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Full text of "Field testing for gold and silver : a practical manual for prospectors and miners"

FIELD TESTING 
FOR GOLD AND SILVER 




DOES IT PAN? 



Frontispiece. 



-FIELD TESTING 
FOR GOLD AND SILVER- 

A PRACTICAL MANUAL 
FOR PROSPECTORS AND MINERS 



BY 

WM. HAMILTON MERRITT, Assoc.R.S.M. 

MEMBER CANADIAN MINING INSTITUTE, LATE, COMMISSIONER 

ROYAL COMMISSION ON MINERAL RESOURCES OF ONTARIO, INSTRUCTOR 
OF PROSPECTORS' CLASSES, ETC. ETC. 



SeconD JEDttfon 




LONDON 
CROSBY LOCKWOOD AND SON 

7 STATIONERS' HALL COURT, LUDGATE HILL 
I9II 

D. VAN NOSTRAND COMPANY 



ye 



Printed at THE DARIEN PRESS, Edinburgh. 



, 



PREFACE. 



THIS little book is the direct outcome of classes held 
for prospectors, my experience in connection with 
them having convinced me that it would be to the 
advantage of the mining man as well as the pro- 
spector if he had a convenient little text-book on the 
FIELD TESTING OF GOLD AND SILVER ORES to 
which he could refer. 

The more I worked with prospectors the more 
convinced I became that the usual blow-pipe sets 
prepared for colleges, etc., were much too complicated 
and too expensive for the field, and that a simpler 
and cheaper set of apparatus was desirable. How 
this want may be met I have endeavoured to show 
in the following pages. 

I do not claim, nor could I claim, any originality 
for the pan-amalgamation process, but by introducing 
a cheap and effective little balance, the procedure, 



VI PREFACE. 

as hereinafter described, enables the operator to get 
definite results in the field with a very cheap and 
portable outfit. 

Indeed, it should be added that the object of this 
work is to demonstrate, in the most practical manner 
possible, how field tests can be made for gold and 
silver with exceedingly cheap and portable apparatus, 
and that tests so obtained are equal to, and may even 
be made superior to, the ordinary assay as conducted 
in the laboratory, with its expensive and stationary 
appliances. 

To meet the demand for the practical, the pro- 
cedure suggested in each class of test is described in 
detail, and tables of the apparatus and ingredients 
necessary are given under their respective numbers, 
the numbers in the case of the apparatus being also 
applied to the illustrations of the same. An operator 
can therefore supply himself with everything necessary 
without much difficulty ; or a dealer will be able to 
put up each class of testing outfit separately, or to get 
together the complete outfit for panning, and the 
outfits for the pan-amalgamation, blow-pipe, and 
furnace "field testing" assays. 

In any case, if the procedure described and the 
apparatus shown are taken in the light of suggestions, 



PREFACE. Vll 

many improvements will no doubt be evolved ; and if 
cheapness and portability are kept in view, as well as 
efficiency, the prospector and mining man will have 
cause to thank those who give the matter their 
attention. 

The mining man and the prospector, nine times 
out of ten, are anxious to supplement their practical 
knowledge with the main scientific principles involved 
in the work they have in hand. I have therefore 
given here in PART II. (PRACTICAL MINERALOGY) an 
outline of instructions which I have found appre- 
ciated in a course for prospectors and miners in 
connection with the practical work in PART I. In it, 
only so much chemistry is given as is involved in 
the comprehension of what a mineral is; sufficient 
mineralogy to enable one to look up a mineral in a 
mineralogical text-book, together with some simple 
confirmatory blow-pipe tests; and enough geology 
to comprise the characteristics of the more common 
rocks. 

I have not hesitated to draw ideas from the excellent 
and modern works of Mr Henry Louis and Captain 
E. L. Fletcher. I have also selected my table of 
minerals and reactions largely from Dr J. C. Foye's 
excellent little book, now out of print, and have 



Vlii PREFACE. 

borrowed some statistical matter from T. F. Van 
Wagenen's booklet on " Hydraulic Mining." 

I must thank various friends and especially Mr 
L. H. Cooke, F.G.S., of the Royal School of Mines 
for some excellent suggestions, of which I have availed 
myself as far as practicable ; and I am also indebted 
to Mr Pellew Harvey, Memb. N.E. Inst. M.M.E., for 
notes bearing on tests by cyanide. 

Many details concerning prospecting, not included 
in this book, can be obtained from Mr Anderson's 
, ' Prospector's Handbook," published by Crosby 
Lockwood and Son. 

WM. HAMILTON MERRITT. 

TORONTO, CANADA. 



CONTENTS. 



PART I. TESTING IN THE FIELD. PAGE 

INTRODUCTORY TO TESTING GOLD ORE IN THE 

FIELD 1 

INTRODUCTORY TO TESTING SILVER ORE IN THE 

FIELD 8 

DETAILED INSTRUCTIONS FOR FIELD TESTS - - 10 

SAMPLING - 10 

PANNING ASSAY --..-..- 14 

PAN-AMALGAMATION ASSAY 15 

FREE-MILLING TESTING OUTFIT ... - 27 

BLOW-PIPE ASSAY FOR GOLD 29 

USE OF IVORY SCALE 36 

BLOW-PIPE ASSAY AND PAN-AMALGAMATION ASSAYS 

FOR SILVER 43 

TESTING CONCENTRATED ORES 45 

BLOW-PIPE ASSAY OUTFIT 46 

COMPLETE PAN- AMALGAMATION AND BLOW-PIPE ASSAY 

OUTFIT 48 

ASSAYING WITH FIELD FURNACE - - . 49 

ASSAYING OUTFIT 61 

ASSAY OF TELLURIDES 62 

ASSAY BY CHLORINATION 63 

ASSAY BY CYANIDE 64 

PROSPECTOR'S OUTFIT 66 

USEFUL INFORMATION 68 

PLACER AND HYDRAULIC MINING 70 



X CONTENTS. 

PART II. PRACTICAL MINERALOGY. 

PAGE 

WHAT is A MINERAL? 75 

MINERALS 77 

TABLE OF COMMON ORES, AND THE MANNER OF 

USING IT 81 

TABLE OF COMMON ORES - 82 

TABLE OF COMMON ROCK-FORMING MINERALS - - 91 

BLOW-PIPE REACTIONS 98 

GEOLOGY 109 

DIAGNOSTIC CHARACTERS OF ROCKS - - - - 115 
TABLE, "CLASSIFICATION OF ROCKS" - -116 

PART III. 

GLOSSARY OF USEFUL MINING TERMS - - .121 
COMMON ROCK-FORMING MINERALS AND ROCKS - 131 



APPENDIX 135 

INDEX - 137 



LIST OF PLATES. 



DOES IT PAN ? Frontispiece 

SAMPLING A QUARTZ VEIN .... facing p. 6 

PROSPECTORS IN A CANOE ,,66 

REPAIRING A SLUICE-BOX .... ,,70 

WHAT is IT? - ,,98 

THE PROSPECTOR'S MOUNTAIN HOME - ,, 119 

HYDRAULIC MINING ,, 124 

SMALL TESTING STAMP MILL - 126 

A FAULT WITH 'SLICKENSIDE' WALLS (Two 

Illustrations) 128 



FIELD TESTING 
FOR GOLD AND SILVER. 



\The numbers under illustrations in each case refer to articles in 
list of outfit. The ton* throughout is taken at 2,000 Ibs. , except 
where otherwise stated, and all valuations are given in the 
decimal currency dollars and cents 4j. 2d. to one dollar, in 
which there are 100 cents^\ 



PART I. 

INTRODUCTORY TO TESTING GOLD ORE 
IN THE FIELD. 

Occurrence of Gold Ores. Gold ore occurs in nature 
in two ways : 

1. Free gold, which can be extracted by mercury ; 

2. Gold in association with other minerals, which 
requires to be smelted or treated by chlorination or the 
cyanide process. 

In field tests, gold ores can therefore be tested by 
amalgamation or by smelting, as hereinafter explained.t 

Free -Milling and Refractory Gold Ores. The first 
class includes " placer " gold and " free-milling " gold ores. 
Free gold varies in its condition, and sometimes, fortu- 
nately rarely, it appears to exist in an allotropic condition, 
which will not amalgamate. Much interesting information 
about gold is found in a " Handbook on Gold Milling," by 
Henry Louis, Assoc. R.S. M., published by Macmillan & Co. 

* That is, the " short ton" now very generally used in America 
and South Africa. 

f For treatment on commercial scale see Appendix A (p. 135). 
A 



2 FIELD TESTING FOR GOLD AND SILVER. 

The second class includes gold locked up in sulphides 
and tellurides of gold and silver, such as sylvanite and 
petzite. 

The cost of treatment of a gold ore depends largely 
upon the condition of the gold in the ore, whether it is 
free-milling or the contrary, known as " refractory." The 
free-milling can be extracted more cheaply than the 
refractory, therefore an ore may be worked with profit 
when in the first condition which would not be possible in 
the second. 

For this reason field tests of gold ores, which will 
determine the character of the ore, are of value to the 
prospector, or indeed to the mining engineer. The latter 
might very frequently supplement an ordinary assay result 
with the procedure hereinafter given under the .head of 
" Pan-Amalgamation Assay." 

A field test may indicate that gold is present, and, as 
generally performed, some idea may be obtained as to 
whether it is present in a large or in a small quantity. 

Panning. The usual test of free-milling gold ore or 
auriferous gravel is " panning." The procedure with gold 
quartz is to pound it up in an iron mortar (Fig. 4) with a 
pestle, and "pan" it down in a gold pan (Fig. 3). 

It will be found advantageous to keep only a small 
quantity in the mortar at a time. 

Pulp. The pounded ore, or "pulp," should be put 
through a sieve into a pan. 

Pan. The ordinary gold pan is made of thin sheet-iron 
or steel, and is usually 16 inches in diameter, 10 inches 
across bottom, with sloping sides from 2^ to 3 inches high, 
and with rounded corners. Great care must be taken that 
there is no grease in the pan. If grease is present it can be 



TESTING GOLD ORE IN THE FIELD. 3 

burned off by heating the pan a dull red heat over a fire. 
The same treatment will also drive off mercury when it 
may have been used in a pan required afterwards for the 
detection of free gold in an ore ; but if gold amalgain was 
present, the pan will still be in a " salted" condition, and 
should be well scrubbed with sand. Separate pans should 
be kept for panning where mercury is used, and mercury 
should in no case ever be used in the pan kept for the 
detection of free gold. 




Fig. 3 and 6. 

Sodium bi-carbonate (" soda ") will also cut grease out 
of a pan, but a prospector will rarely have enough to 
spare for this purpose. 

Operation of Panning Pulverised Quartz. To pan the 

pulp, the pan is generally sunk under water, and the pulp 
is thoroughly mixed with the water until it is all in a state 
of suspension in the pan, which is then agitated with a 
circular motion, so that the heavier particles will naturally 
settle to the bottom. The pan is then lifted, and the 
pulp in suspension is carefully poured off. 

Slimes. This impalpably fine pulp in suspension in 
water is known as " slimes." The pan is then raised out 
of the water, and a circular and side-shaking motion is 
given to the pan, which gradually shakes the lighter 
portions of the pulp to the edge of the pan. The edge is 
scraped off, the pan dipped into the water, a small amount 



4 FIELD TESTING FOR GOLD AND SILVER. 

of which is taken up in order to further assist the sinking 
of the heavier portions and the floating off of the lighter. 

Tailings. The refuse rock matter thus separated is 
known as "tailings." The agitation being continued, 
more tailings will be floated off, or scraped off, from the 
pan, and so on until all of the rock matter has been taken 
away from the mineral matter (or " concentrates ") which 
is left in the pan. 

Concentrates. The concentrates are then further 
panned out, if they are present in any considerable quan- 
tity, until a small quantity remains. The pan is then 
taken out, a little water is put into it, and it is held facing 
the operator, who gives it a side motion with a little jerk 
in one direction, washing the water back and forth. The 
concentrates and the heavier material will go in the direc- 
tion of the jerk, and finally a tail of gold will be seen at 
the extreme end of the remaining concentrates. 

By this means we obtain the presence or absence of 
free gold, but to an indefinite amount. The experienced 
operator soon gets into the habit of estimating pretty 
closely the value of an ore to which he is accustomed, 
but if there is flake gold or much fine gold, or if the gold 
is nuggety or very irregular in its dispersion, the result 
by guessing may be then very misleading. 

Panning Gravel. In the case of gravel the same 
principles apply. More material is generally taken than 
when panning pulverised quartz, and the panning can be 
done more quickly, because the gold is much coarser as a 
rule. A pan * holds about 20 Ibs. of gravel. After the 
first circular shaking motion under water, the bigger stones 

* The placer miner's pan is usually larger than Nos. 3 and 6 
herein mentioned, which hold 15 Ibs. of grave) 



TESTING GOLD ORE IN THE FIELD. 5 

are scraped together, washed in the water which is in 
the pan, and then thrown out. The operator continues 
shaking the pan under water to allow the gold to work to 
the bottom, and washing and throwing out the heavier 
gravel until only fine gravel and sand are left, when the 
procedure is similar to the panning of crushed quartz. 
Finally, with the gold (if any) "black sand" (magnetite) 
is associated, and often iron pyrites and galena, etc. 
Much care is then necessary to wash this heavy concen- 
trated matter away and leave the gold by itself at the 
extreme tail. 

Qualitative Determination. The above is what is called 
"qualitative" estimation, but by proceeding systematically, 
and weighing both the material used and the product 
obtained, the "quantitative," or exact result, can be 
obtained with practically the same amount of trouble as 
the rough and ready method of guessing. 

Quantitative Determination. This being the case, it 
certainly would appear that a method by which any one 
can determine in the field the exact amount of gold per 
ton obtainable from the ore would be of considerable 
value to the prospector, and much more satisfactory than 
a mere guess at the result ; and if this can be obtained 
by an inexpensive and convenient apparatus, it certainly 
ought to be decidedly in the interest of prospectors to 
systematically test their ores in the field by it before 
spending a great deal of time and money upon them 
based on guess-work. 

This was the motive which led to the " outfit," enume- 
rated below, being got together, for with it a test of this 
character can be conducted. 

More commonly the benefit of such testing will be 



6 FIELD TESTING FOR GOLD AND SILVER. 

undoubtedly to prove to the prospector that the vein or 
gravel which he has been paying attention to cannot, in 
its present condition, pay to work, and therefore he will 
be saved much time and money by proving this fact. Any 
one who has done much assaying, or has frequented an 
assayer's office, and seen the average results obtained from 
specimens brought in, will be convinced of the truth of this. 

If a prospector cannot get a paying result out of his ore 
or gravel by the simple field methods hereinafter described, 
he need not expect that a conscientious assayer can 
squeeze something out of nothing, and he will moreover 
have obtained a result in the field, in his tent, of consider- 
ably greater value than the usual assayer's fire test. 

In carrying out a field quantitative estimation of the 
value of gold ore, most men will only determine the amount 
of free gold, but if the operator is experienced, and 
practises, he can make estimations of the amount of gold 
in concentrates, or in refractory ore, by the smelting or 
blow-pipe process, or by assay in a field-furnace, and 
measurement of (or weighing) the resulting bead obtained 
therefrom. 

The procedure in these different classes of field tests 
is given further on, together with a description of the 
apparatus which is necessary to arrive at the results. 

Auriferous sand or gravel can be treated, and the yield 
estimated, in the same way as free-milling gold ore. 

Sampling. One matter of immense importance in esti- 
mating the value of every kind of ore is the " sampling." 

This is particularly the case with gold ore, for a very 
small piece of gold more or less in the sample makes a 
tremendous difference in the estimated value of the vein 
or deposit. 




SAMPLING A QUARTZ VEIN. 



\_Tofacep. 6. 



TESTING GOLD ORE IN THE FIELD. 7 

The sample of any material should represent the average 
of the vein or other deposit, so far as exposed by develop- 
ment, at the time when the sample is taken. 

Selected Specimens. Most prospectors get their samples 
from various outcrops of veins or other deposits, and 
most of the samples are small pieces, which are carefully 
selected. The prospector with experience can, if he wishes 
it, select samples which may pretty well represent the 
average of the mineral deposit. In gold ore, however, 
this is very difficult to do, for where the gold is in a free 
condition in the rock, and not visible to the eye, it often 
occurs so disseminated through the ore that any attempt 
at selecting may lead to the most valuable part being 
thrown away and the less valuable retained. 

On the other hand, if the gold is in a refractory state, 
and associated directly with other minerals in the ore, by 
selecting out the mineral it is associated with it is possible 
to make a selection of the ore. 

Selected specimens are generally not only unsatisfactory 
to the capitalist or promoter, but even the prospector may 
often find he has lost more in time and money in the 
long run through the subsequent disappointment which 
inevitably arises on account of an unfair selection. 

Average Sample. An "average sample" is what should 
be obtained, viz., one that will represent the result which 
may be expected by mining and treating the ore or gravel 
on a large scale. 

Therefore the suggestions concerning sampling should 
be carefully observed, and the simple appliances in con- 
nection therewith are noted below. 

The directions which follow have reference to treating 
the ore as it runs, but it is quite feasible to pan down an 



8 FIELD TESTING FOR GOLD AND SILVER. 

ore and merely treat the concentrated result. In doing 
this, however, there is a likelihood of losing fine leaf and 
float gold, which would to a greater or less extent be taken 
up by the mercury in the direct pan-amalgamation test. 
The concentrated result can be treated directly by the 
blow-pipe method, or the free gold can be extracted from 
it previously by mercury. 

Owing to small yield of most ground, auriferous sand or 
gravel will generally require preliminary concentration 
before treating by pan-amalgamation, 10 or 20 to 1, 
and allowance for this will then be made when weighing 
the resulting bead. In most cases, however, it will be 
more satisfactory to proceed with the testing of ore from 
a vein in the manner hereinafter described. 



INTRODUCTORY TO TESTING SILVER ORE 
IN THE FIELD. 

The commoner ores of silver are 

" Silver- Lead" (argentiferous galena). 

Native Silver. 

Argentite, or black sulphide. Silver, 87 per cent. 
Ag 2 S. 

Tetrahedriie, argentiferous grey copper ore, or copper- 
antimony silver ore. 4Cu. 2 S -f Sb 2 S 3 . (Silver replacing 
copper in variable proportions.) 

Pyrargyrite, ruby silver, or dark red silver ore. Silver- 
antimony sulphide. Silver, 60 per cent. 3Ag 2 S, Sb 2 S 3 . 

Proustite, or light red silver ore. Arsenic-silver sul- 
phide. Silver, 65*4 per cent. 3Ag 2 S, As 2 S 3 . 

Stephanite^ or brittle sulphide of silver. Silver, antimony, 
arsenic and sulphur. Silver, 68*5 per cent. 5Ag 2 S + Sb 2 S 3 . 



TESTING SILVER ORE IN THE FIELD. $ 

Polybasite, or antimony (arsenic, copper) silver sul- 
phide. Silver, 72 per cent., when no arsenic or copper. 
9Ag a S + Sb a S 8 . 

Cerargyrite, or horn silver. Silver chloride. Silver, 
75*3 per cent. AgCl. 

Hessite^ or telluric silver. Silver and tellurium. Silver, 
62 per cent. Ag 2 Te. 

In most cases much the most convenient manner in 
which to test a silver ore is by smelting with a blow-pipe, 
using lead to take up the silver, and then getting a silver 
bead by cupellation. As a rule this will be done in a 
qualitative manner, and if the galena, or other substance 
tested, is found to carry silver, the size of the bead will, 
with a little practice, give a general indication as to 
whether the ore is worthy of a quantitative assay or not. 

By using a Plattner's ivory scale, the size of the button 
will give the exact yield of the ore. 

It is safer for the prospector to place no value upon the 
lead. 

An ore which is found to carry silver, and not too much 
lead, could be tested qualitatively by pan-amalgamation, 
by treating it somewhat in the same manner as a gold ore, 
but previous roasting is necessary in the case of rebellious 
ores, or those which contain, especially, arsenic and 
antimony. 

A large quantity of lead necessitates a smelting test by 
blow-pipe or a fire assay. 

Particulars of the manner in which the operations, 
mentioned in this and the previous pages, are conducted 
will be found in the detailed instructions which follow. 



10 



FIELD TESTING FOR GOLD AND SILVER. 



DETAILED INSTRUCTIONS FOR FIELD 
TESTS. 



SAMPLING. 

Take ore in equal proportions across the vein from 
wall to wall (or across the " pay-streak "), or in alluvial 
deposits from pits sunk through the strata. If sample 




Fig. F. Quartering 
(Second Heap). 




Fig. E. Cross-Cutting (First Heap). 



is a large amount, as from a u cross-cut," make a smooth 
place on the ground. On this place the samples are 
thrown in a pile. The pile should be shovelled over after 
breaking the pieces to the size of macadam ; or if the pile 
be too large, cut through it at right angles (Fig. E), throw- 
ing the rock from the trench thus made in a pile by itself 
(Fig. F). 

Quartering. This should be broken smaller, mixed well 
by shovelling, and made into a low truncated cone, which 



SAMPLING. 



II 



is divided into four equal parts by making a cross on the 
surface, and throwing out two diagonal quarters, which 
are again reduced in size, made into a second similar 
cone, and treated as before. This process is known as 
" quartering." 

The quartering and breaking with a heavy hammer 
(Fig. 63) is continued until the sample is small enough to 




Fig. 63. 

handle on the mixing cloth, on which the remaining 
portion is shovelled, care being taken that the proper 
proportion of " fines," or pulverised ore, is taken, for the 
highest values are often in them. 

The mixing cloth is a smooth-surfaced ( 
waterproof sheet, about 4 feet square. 
It is used best by two people taking 
the four corners, and the sample is rolled 
about by lifting each corner in turn until 
it has been thoroughly mixed on the 
cloth. Then the four corners are lifted 
together, and the cloth laid down and 
spread out. (One person can mix less 
advantageously by lifting each corner in 
turn.) The pile of ore in the centre is 
then flattened, and a thin sheet of iron (such as in Fig. 
12A, page 20), or wood, is used to cut through the ore, 
dividing it into four quarters. Two opposite quarters are 
scraped off on to a piece of smooth wrapping paper or 




Fig. 4. 



12 



FIELD TESTING FOR GOLD AND SILVER. 



newspaper, partly laid under the edge of the mixing cloth, 
the fines being brushed off with brush (Fig. 2). 

(In the case of a smaller sample, the mixing cloth can 
be used from the start.) 





Fig. 2. 



Fig. 31. 



Then pound up in mortar to size of beans. Roll round 
in mixing cloth, quarter down as before described, brush- 
ing away rejected quarters with wide " varnishing brush " 
(Fig. 2). Keep on mixing and quartering down until 
between 2 and 3 Ibs. remain. Dry this thoroughly, pound 
it in mortar, and put it through a 40-mesh sieve, unless 




Fig. 5. 

you know gold is very fine, in which case a 60-mesh sieve 
should be used. Dump any residue that will not go 
through sieve on a clean piece of paper. Remove iron 
scales by magnet (Fig. 31), clean any gold scales in weak 
nitric acid, dry them and throw them in with pulp. 

Getting Sample for Assay. If it is desired to get a 
sample for fire assay, again mix and quarter down the pulp 



SAMPLING. 



on the mixing cloth until a few ounces remain, brush this 
off the mixing cloth and send it to an assayer, or keep it 
for blow-pipe assay or for assay in field assay furnace. 

Weighing out 2-lb. Sample. The consideration of 
rough scales is a matter of some importance. Any scales 
that weigh from J oz. to J lb., or a 
greater amount, will serve the pur- 
pose. The cheapest and lightest 
scale is one used for weighing letters 
(Fig. 10), which weighs from J oz. to 
12 oz. ; but a better scale is a light 
spring balance, weighing up to 2 Ibs., 
and divided into J and J oz. The 
latter scales are best for obtaining 
specific gravities, mentioned here- 
after (p. 79). 

The sample can best be weighed 
by laying it on a sheet of paper, 
turning up the edges, and tying 
them with a piece of string which 
can be hooked on to the scales. 

Ingenuity can be displayed in this matter of weighing 
rock, gravel, or pulp ; and a box or tin to hold a certain 
quantity of broken quartz, gravel, or pulp could be used 
as a measure in place of weighing. 

Weigh the bulk of the pulp now remaining on the 
rough scales (Fig. 10). We will suppose it weighs 2 Ibs. 
6 oz. Mix the pulp on the mixing cloth, flatten the little 
pile, and weigh out 6 oz. from different parts of the 
flattened pile, brush the remaining 2 Ibs. off the cloth into 
an ordinary gold pan. 

This procedure for sampling out 2 Ibs. wil apply 
equally to auriferous sands and gravels. 




Fig. 10. 



14 FIELD TESTING FOR GOLD AND SILVER. 

PANNING ASSAY. 

Panning assay consists merely in panning down a 
certain weight of gravel or pulp, and then weighing the 
resulting free gold, which has been obtained simply by 
the mechanical operation of panning. This method is 
more particularly useful in placer deposits, where it is 
desirable to estimate the average yield of the gravel, 
because the operation of washing gravels is more purely 
mechanical than the amalgamation of crushed quartz in the 
stamp mill, even though, in the former case, mercury is used. 

In the case of gravel, an amount can be weighed out, 
or the panful estimated at 20 Ibs.,* and then the gold 
which is obtained is carefully weighed on the little scales, 
which weighs to 5 grains (Fig. 11). 

For example, if from 20 Ibs. we get 2 grains of gold, 
there would be 2x100=200 grains (*4 oz.) of gold in a 
ton (2,000 Ibs.) of gravel, which, at a value of $17'00 to 
the oz., gives $6'80 to the ton, or to give latitude, bettei 
say to the cubic yard of gravel. 

This is an example of a very high yield, and in most 
cases, as already indicated, it will be advisable to pan 
down several pans of the gravel, say ten pans to one pan 
of partially concentrated material, and in panning this 
down we get the yield of 200 Ibs. of gravel. Again, if the 
amount of gold panned out weighed 2 grains, multiplying 
by 10 gives the yield of a ton (or, as before, a cubic yard) 
of gravel, which in this case would be 68 cts. 

In the case of crushed quartz, or pulp, the panning 
assay can be done from 2 Ibs. of ore (obtained as set forth 
under " Sampling " above), which is very carefully panned 

* Namely, for larger size placer pan, or 15 Ibs. for usual smaller 
gold pan of quartz miners. 




PAN-AMALGAMATION ASSAY. 15 

down until the visible free gold is panned as free as 
possible from sulphurets. This is then dried, brushed 
into a little cone of lead- foil, rolled up, melted and cleaned 
with borax and soda, and cupelled. The procedure is 
described hereafter under the pan-amalgamation assay 
which immediately follows, and the manner of estimating 
the result is also given. 

The advantage of this method is that it saves the trouble 
of mercury amalgamation and, if the gold is very coarse 
and free, it is a quicker manner 
of arriving at the same con- 
clusions. Fine and float gold, 
however, are very apt to be lost. 

If weight of pack makes it im- ^Fig.' X." Horn, 

possible to take a pan, a " horn " 
(Fig. X) can be used, but it is by no means so effective. 

PAN-AMALGAMATION ASSAY. 

Making Sodium Amalgam. To the 2 Ibs. of pulp add 
enough water to make an easily stirred paste. Weigh 
out 1 oz. of mercury on rough scales. This can be done 
by suspending a piece of paper by the four corners by 
string, or suspending' the porcelain thimble. Then put 
the mercury in a porcelain dish or granite-ware saucer, 
or in the bowl of a clay-pipe, the aperture of which has 
been stopped up from the inside by bone-ash or clay. 
The mercury is then heated, and a little sodium* of the 
size of a small pea is added which unites with the mercury 
with a slight flash, forming sodium amalgam. 

Mixing Pulp with Sodium Amalgam. This is at once 
thrown into the pulp, and it is stirred for an hour with a 

* Or solid sodium amalgam may be used, which can be carried 
in a well-stoppered bottle, in place of metallic sodium. 



1 6 FIELD TESTING FOR GOLD AND SILVER. 

wooden pestle. If too much sodium is used it will 
amalgamate with pan. 

In some cases it may be found that a piece of potassium 
cyanide, the size of a pea, will brighten the gold and 
mercury, and assist amalgamation. When used, a dupli- 
cate without it should be made to ascertain proportion 
of fine gold it may have dissolved. 

In place of stirring in a pan the pulp can be shaken 
with the mercury in a large bottle, in two lots. After the 
water and the mercury are put into the bottle with the 
pulp, the bottle is then tightly corked, and the contents 
agitated violently for about thirty minutes. Towards the 
end of the process, the bottle is shaken more on one side 




Fig. 16. 



to give the mercury an opportunity of coming together. 
The pulp in the bottle (or bottles) is then washed out 
into the pan by adding water and shaking the-bottle until 
it is quite clean. 

The pan containing the pulp is then stirred up under 
water so that all the mercury gets an opportunity to settle 
to the bottom. The slimes are allowed to slowly run off. 
An empty pan is then sunk to the bottom of the tub, or 
quiet pool of water, and the other pan, with the pulp in 
it, is panned over the top of the sunken pan, so that the 
tailings and concentrates fall into it. 

Panning Out Mercury. When it is noticed that the 
mercury has settled into one spot, and that if the panning 
were continued further there might be some danger of 



PAN-AMALGAMATION ASSAY. f] 

losing it, it is run off by letting the water drain out of the 
pan, and then making a little channel with the finger 
through the centre of the pulp, and the mercury will run 
to the other side of the pan, and then it is carefully run 
into a granite-ware cup. 

The panning is then continued until all the tailings 
and most of the concentrates are panned away into the 
sunken pan. As much of the mercury as possible is then 
run with the rest into the cup, and the concentrates 
remaining, together with any floured mercury, are washed 
into a granite-ware saucer. The concentrates in the 
saucer can then be panned down further and the floured 
quicksilver, if any, is readily collected together by adding 
a little piece of sodium and stirring it about, after the 
water has been drained off the concentrates. 

The action is assisted if the water has previously been 
warmed a little, in fact, if possible to prevent it, water 
colder than from 60 to 70 should not be used, as it 
makes the mercury more liable to flour. 

We then have the mercury collected in the cup, and 
some concentrates already panned out. 

The first-mentioned pan is now sunk in the water, and 
the pan, into which the tailings and concentrates were 
run, is taken out and repanned into the other pan to see 
if any quicksilver has escaped. 

These first two pannings, for the mercury alone, are 
made comparatively quickly, and without as much care 
as is necessary to pan out the concentrates afterwards. 

Cleaning the Mercury. The mercury is then washed 
by stirring it under water, and washing out any concen- 
trates. The water is then drained off and it is dried with 
blotting paper. 



1 8 FIELD TESTING FOR GOLD AND SILVER. 

The mercury is now weighed on the rough scales to 
see if it has all been got back again. 

If there is considerable loss through flouring, or on 
account of the presence of a great deal of heavy fine 
concentrates, the tailings are repanned to recover the lost 
mercury. A loss in mercury may occasion a corresponding 
loss in gold, therefore it is only reasonable to allow a 
proportionate amount of gold in addition to the final 
result for the mercury which is lost. If there is a distinct 
loss in mercury it is safer to try the test over again. 

Panning Out Concentrates. We now sink the other 
pan and pan the tailings carefully into the sunken pan for 
concentrates. The concentrates are washed out into the 
saucer which contains those obtained from the first pan- 
ning for the mercury. The sunken pan is then again 
raised and the tailings in it are once more panned for 
any final concentrates that may have escaped. This last 
time the tailings can be panned away without sinking a 
pan to catch them. 

Estimating Proportion of Concentrates in Ore. 
Weigh the concentrates which have been recovered, after 
drying them, divide their weight in ounces, and fractions 
of an ounce, into the number of ounces taken for treat- 
ment. (In the case of 2 Ibs. this will of course be 32 oz.) 
The result will give the number of tons of ore it takes 
to yield a ton of concentrates. For example, if J oz. of 
concentrates is obtained from 2 Ibs. of ore, ^ divided into 
32 gives a result of 64 tons of ore to yield 1 ton of 
concentrates. 

In such a case 64 divided into the value of the concent 
-rates (when obtained), will give the yield of ore per ton 



PAN-AMALGAMATION ASSAY. 19 

through their concentrates, after the free gold has been 
extracted by amalgamation. 

Separating Gold from Mercury. The gold is separated 
from the mercury, by retorting it either in a small cast- 
iron retort (Fig. 12), with a cover and pipe to collect the 
mercury, or in a little Russia iron retort supported in a 
sheet of the same material (Fig. 12A). 




Fig. 12. 

It can also be separated by dissolving away the mer- 
cury and silver by nitric acid.* In the case of retorting 
we get the most of the quicksilver back, and it is not 
necessary to carry about as much nitric acid. 

When the cast-iron retort is used, a rag should be 
wrapped round the pipe, and kept wet "while retorting, to 
condense the mercury which is run into a cup with some 
water in it, the end of the pipe being kept just above the 
water. The lid of the retort is luted with asbestos paper 
or wood ashes, and a fire is built around it, the heat 
being brought on gradually. A small piece of brown 

* For this purpose the porcelain dish can best be used, or the 
granite-ware cup. 



20 



FIELD TESTING FOR GOLD AND SILVER. 



paper under the mercury in the retort will prevent the 
gold sponge from sticking to the bottom. 

In the case of retorting with the Russia iron retort, 
the sheet of Russia iron supporting the retort is placed 
on bricks or stones, and a little fire built underneath. 
The Russia iron reto'rt is covered by a large potato, 
which is hollowed out, or an inverted crucible, if it is 
desired to save the mercury or to avoid its pernicious 





Fig. 12A. 

fumes. It is better to cover the mercury in the little 
retort with a small disc of asbestos paper to avoid 
spurting. 

Cleaning Gold Sponge. The gold bullion obtained as 
a sponge in the bottom of the 
retort readily comes out if scraped 
with a knife, and it is then dumped 
on a sheet of paper. This sponge 
is wrapped in a little pure sheet 
lead, or mixed with some pure 

grain lead, and melted in a small hole in charcoal by 

the blow-pipe. 




Fig. 2G. 



PAN-AMALGAMATION ASSAY. 



21 



The blow-pipe is a tube of some metal in varying shapes. 
One sort is seen in Fig. 24 and another in Fig. 24A. A 
" grease-pot " (Fig. 23), or a miner's candle with a large 
wick, gives the flame. If the grease-pot is used, it should 




Fig. 43. 

be heated until the grease is melted and the wick hot and 
soft. The blast is given to the blow-pipe by inflating the 
cheeks and breathing through the nose, while the pressure 
of the cheeks gives sufficient 
force to the flame, which should 
be steady and continuous. 

An artificial blast, given by 
two indiarubber balls, with 
valves (Fig. 43), can be used, 
but this is more useful where 
a smelting process on a little 
larger scale is undertaken. 

The blue point of the flame 
is used to melt the lead. A 
small amount of borax and soda 




Fig. 23. 



is then added, and the lead button is again fused in 
contact with the molten flux, any impurities thereby 
being abstracted. The lead is then allowed to become 
quite cold. 



22 FIELD TESTING FOR GOLD AND SILVER. 

Cupelling 1 . A cupel is made by filling the bowl of a 
clay-pipe (Fig. 25) three-quarters full of dry earth, or 
some other material, and rilling the remainder with bone- 
ash, press down with round end of a bolt, and dry with 



Fig. 24. 

flame of blow-pipe. The lead button is then taken out of 
the charcoal, squared on the little anvil to clean it from 
slag, and gently placed by the pincers in the cupel. 




Fig. 25. 

Cupellation is then carried on by melting the lead button 

beyond the blue point of the blow-pipe flame, and keeping 

. the bead slowly rolling on the cupel until all is absorbed 



but the gold and silver. If the button is black from 
copper, more lead is added, and cupellation continued 
until the button is \vhite or yellow. 

The lead is oxidised and finally all absorbed when the 
silver button will "blick" or flash. For further details 
about cupellation see "Silver' 3 under " Blow-pipe Reac- 
tions" in the latter part of this book. 



PAN-AMALGAMATION ASSAY. 23 

The button is detached from the cupel by forcing the 
point of the small blade of a penknife gently between it 
and the bone-ash. It is cleaned by being placed between 
a folded piece of paper and rolling it beneath the finger 
on a smooth surface. 

Value of Bullion Bead. The colour -of the resulting 
bead. will be a guide as to the purity of the bullion. If it 
is very yellow, the bullion may be classed at about $18 an 
ounce. If a little lighter colour, from $16| to $17J ; and 
if quite a light yellow, from $15 to $16|. 

In the case of the resulting gold where the mercury is 
dissolved in nitric acid, it may be treated as pure gold, 
and valued at $20 an ounce, after treating it exactly as 
the sponge resulting from retorting. 

Parting". If the button does not appear distinctly 
yellow, it will be better to dissolve it in a little nitric acid,* 
and then remelt the resulting gold, if any, with lead, and 
cupel it as before. It will then be valued at $20. 

If, however, there is enough gold still to prevent it from 
dissolving, wrap the button in some silver-foil and melt it 
with the blow-pipe in the cupel; then, when there is more , 
than twice as much of silver as of gold, the button will 
"part," /.., the silver will dissolve out. 

Weighing Gold Button. -The button is then weighed 
on the little scales (Fig. 11), which weigh up to 5 grains, 
and are divided into one-tenth of a grain. 

Every grain of gold (or bullion) obtained in the result 
is equal to about 2 oz. of gold per ton (2,000 Ibs.) of ore 
when 2 Ibs. of pulp are taken for treatment. 

We will suppose an ordinary yellow gold button has 
been obtained by retorting, and we value the bullion at 

The porcelain thimble is most conveniently used for this purpose 



FIELD TESTING FOR GOLD AND SILVER. 



$17^ per ounce. Every grain on the little balance will 
therefore represent 2 x 17, viz., $35 ; therefore each tenth 
of a grain, or each mark on the scale, will represent $3'50 
per ton of ore, and as it is quite possible with practice to 
read to half a division on these scales, therefore a result 
as low as $1*75 per ton can readily be estimated. 





Fig. 11. 

Concentrates. Having obtained the result in free gold, 
the concentrates can be treated as follows : Calcine 
t.e. 9 roast some 4 or 5 grains of them quite sweet, 
which is readily done by spreading them in a thin layer 
in a shallow cavity on charcoal, and roasting them beyond 
the blue point of the blow-pipe flame. Then repulverise 
them and re-roast them until there is no smell of sulphur. 

Smelting Concentrates. The calcined concentrates are 
mixed with an equal quantity of litharge (oxide of lead) 
and some borax and soda, the quantity of the latter two 



PAN-AMALGAMATION ASSAY. 25 

ingredients varying as the concentrates contain more or 
less silica. The more silica, or quartz, the more soda, 
or the more iron or lime the more borax. 

As a rule it will generally be safe to take a little more of 
borax than of ore, and less than the same quantity of soda 
as of ore, more soda being added if the concentrates are 
not quite clean and have some quartz left in them. 

This mixture is then smelted in a small cavity in char- 
coal (Fig. 26), adding more and more as lead button 
increases in size, and keep turning to compel big button 
to gather small ones. When all the lead is reduced it is 
treated as per pp. 21 and 22. 

Qualitative Result from Concentrates. The resulting 
button of lead, obtained from the fusion of the above 
mixture on charcoal, is then cupelled on the clay-pipe 
(Fig. 25), and if a visible button of gold is obtained, the 
concentrates will be worth having an assay made of them. 
If the resulting button is light coloured, it should be dis- 
solved in a little nitric acid ; and if it will not dissolve, 
there is less than two parts of silver to one of gold present 
in the button, the button being chiefly gold ; but if there 
is more silver than that, it will leave a black porous 
sponge of gold, or some flakes of the same colour, which 
will show the presence of that metal. 

Annealing. On heating to dull redness in the porcelain 
dish, the black flakes or sponge of gold will turn a gold- 
yellow colour. This is termed "annealing," and it is 
generally done when working with the blow-pipe in the 
little porcelain thimble, which is held by the pincers, and 
the flame is directed by the blow-pipe to the spot above 
which the gold flakes lie. If the black flakes should be 
carbon, they burn away. 



26 FIELD TESTING FOR GOLD AND SILVER. 

Result. The above treatment has determined the 
amount of free gold there is present in the ore ; it has 
shown the number of tons of ore necessary to yield 1 
ton of concentrates, and it has revealed the fact that the 
concentrates carry gold, or that they do not, and a rough 
guess can be made at the amount of gold they carry from 
the size of the resulting button. 

Example of Results from a Free-Milling Ore. 

Free Gold. Button of bullion was yellow and weighed 
I'l grain, at $18 an ounce (18x2x ri) = $39-60. 

Concentrates. 2 Ibs. yielded \ oz. Therefore (32-r-J = 
128) it takes 128 tons of ore to yield a ton of concentrates. 
Some of the concentrates treated as above described for 
gold yielded a small button of gold. 

Roasting Refractory Ore. In the case of an ore com- 
posed chiefly of sulphurets, and which has been proved 
to contain no free gold, 2 Ibs. can be roasted quite 
sweet, care being taken to do it very gradually, with con- 
stant stirring to prevent " fritting " or fusing. This may 
be done in a pan, or in a species of iron ladle, which 
prospectors sometimes use for the purpose. It can then 
be treated by pan-amalgamation exactly as above, and in 
many cases a fair idea of the amount of gold present in a 
refractory state will be obtained. 

Roasting Concentrates. In the case of concentrates, 
if the operator takes the time to pan out 2 Ibs. (or a 1-lb. 
test can be made), he can proceed with them in the same 
manner as with the refractory ore just mentioned. 



FREE-MILLING TESTING OUTFIT. 27 

FREE-MILLING TESTING OUTFIT. 

The following is a list of articles required in field work, 
it being taken for granted that the prospector is already 
in possession of a rough knife for scratching minerals, a 
pocket compass , and a small magnifying glass. 

Sampling. 

1. " Mixing cloth/' or smooth waterproof sheet, 4 feet 
square. 

2. Brush, broad (varnishing brush). 

Panning. 

3. Gold-pan, Russia iron (not to be used with quick- 
silver). 

4. Iron mortar (5 inches x 6 inches) and pestle. 

5. Sieve, brass wire, 40-mesh, in tin dish with cover. 

Pan-Amalgamation. 

6. Two gold pans, one ordinary iron, the other granite- 
ware. 

7. Nitric acid, strong, in 2-oz. glass-stoppered bottle, in 
'' patent lightest weight liquid mailing case." 

8. Mercury, 1 Ib. in bottle, in " patent lightest weight 
liquid mailing case." 

9. Sodium, \ oz. in bottle, with naphtha, in " patent 
lightest weight liquid mailing case." 

10. Hand-scale, "traveller's letter and parcel balance," 
weighing J oz. to 12 oz., for weighing mercury and ore ; 
or, if obtainable, Salter's spring balance, \ oz. to 2 Ibs. 

11. Balance hand-scale with sliding weight on beam, 
very sensitive, from 0*1 to 5 grains, for weighing beads of 
bullion and weighing out charges for quantitative blow- 
pipe assay. 



28 FIELD TESTING FOR GOLD AND SILVER. 

12. Small-sized mercury retort (2x2j inches), with 
close-fitting cover and pipe to collect mercury ; or, 

12A. Mercury retort, small, Russia sheet-iron, Ijxlf 
inches. Also sheet of Russia iron, 8 inches square (with 
a hole for supporting the Russia iron retort in the centre), 
for quartering when sampling. 

13. Porcelain dish and two porcelain thimbles (small, for 
parting in). 

14. Granite-ware cup and saucer, small size. 

15. Brass wire sieve, 60-mesh. 

16. Wooden pestle. 

17. Sheet lead, pure, 2 oz. 

18. Sheet silver, pure, oz. 

19. Borax glass, ground, 1 oz., in deep round tin box. 

20. Soda, 1 oz., in deep round tin box. 

21. Litharge, 4 oz., in deep round tin box. 

22. Bone-ash, 2 oz., in deep round tin box. 

23. Paraffin lamp, tin, with - Ib. paraffin. 

24. Blow-pipe. 

25. Two clay pipes, one, mounted, for cupelling, the 
other for heating mercury. 

26. Charcoal, three pieces, sawn square. 

27. Pincers for small lead buttons. 

28. Steel anvil, J x 1 J x 2 inches. 

29. Small piece thin asbestos card. 

30. Hammer, small. 

31. Magnet. 

32. Smooth-headed bolt, for making cupels in clay-pipe. 
This outfit will determine the value of free-milling ores 

as low as of any commercial value ; it will enable the pro- 
portionate yield in concentrates to be estimated, and the 
concentrates to be qualitatively tested as to their precious 
metal contents. 



BLOW-PIPE ASSAY FOR GOLD. 29 

BLOW-PIPE ASSAY FOR GOLD, 
OR QUANTITATIVE DETERMINATION OF CONCEN- 
TRATES AND REFRACTORY ORES. 

The above is all that most prospectors will care to 
know, but in the case of mining engineers or advanced 
students in blow-pipe work, the actual yield of the con- 
centrates (or of refractory ores) can be determined in the 
field by measuring the resulting button on Plattner's ivory 
scale (Fig. 33) ; or in the case of very rich ores, or where a 
comparatively large amount of the material is smelted 
in a field assay furnace. The resulting button may be 
weighed on a portable little beam balance (Fig. 44). 

Sampling. The sampling has already been described. 
In the case of concentrates obtained from the pan-amal- 
gamation process, they are carefully calcined, as already 
noted, pulverised still finer, and the sample to be tested 
is obtained by flattening the roasted concentrates, after 
thoroughly mixing them, and taking small portions on the 
point of a knife from different parts. 

In the case of smelting, or any other, ore, the pro- 
cedure is exactly the same as with the concentrates, 
except that if it has not been put through the amalga- 
mation process, the procedure will vary, as laid down 
further on in " Sampling and Metallics" under "Assaying 
with Field Furnace," for the pulp may carry metallic flakes 
of gold or silver, which will be caught upon the screen, 
and will alter the result of the 
test. 

Calcination. The roasting is 
most easily performed by plac- 
ing a small quantity of pulverised 
concentrates, or pyritous ore, in Fig. 36. 

a little fire-clay capsule (Fig. 35), placing it on the 




30 FIELD TESTING FOR GOLD AND SILVER. 

Fletcher's furnace (Fig. 36), with the cover off, and blow- 
ing the flame gently upward through the side hole, 
occasionally stirring the concentrates. 

Charging.* If the ivory scale is used, 3 grains of 
roasted concentrates are weighed out on the little scales 
(Fig. 11), 3 grains of soda, 5 grains of borax glass, 6 
grains of litharge, and \ grain of flour. These are mixed 
together and put into a little clay crucible (Fig. 34), by 
being brushed into it from a folded piece of paper by a 




Fig. 34. Fig. 37. Fig. 35. 

small camel's hair brush (Fig. 37). The crucible is then 
covered with a little salt, and a pin, or small piece of iron 
wire, is thrust into it if there is any danger about the 
concentrates not having been roasted quite sweet. 

Fusion in the Blow-pipe Furnace. The smelting is 
performed in the above-mentioned little fire-clay crucible 
(Fig. 34) in a small Fletcher's furnace, with side hole 
(Fig. 36), by means of the flame from a spirit lamp (Fig. 
42), blown by a large-nozzled Black's blow-pipe (Fig. 24A). 

To blow in the furnace, it is placed on an upturned 
assayer's crucible, or on a brick, close to the edge, and 
the spirit lamp (Fig. 42) is held so that the wick comes 
just below the side hole of the furnace, close to it, in such 

* Notes on fluxes and charging occur (p. 50) under "Assaying 
with Field Furnace " further on, and the same principles apply here. 



BLOW-PIPE ASSAY FOR GOLD. 3! 

a position that the whole flame can be blown into it by the 
blow-pipe. 

The flame is blown upwards through the side hole, 
commencing to heat gradually, then increasing the force 
till the interior grows orange red, and when finished all 
bubbling will have ceased, and the slag be quite clear on 
the top of the little pot. The time taken will be from 
four to eight minutes. Care must be taken not to continue 
it long, or the pot will be eaten through and the charge 
escape. The oxidisable metals, such as iron, tin, and 
cobalt, combine with, the slag, and leave nickel and 



Fig. 24A. 

copper, as well as gold and silver, with the lead. When 
the crucible has cooled it is broken up... 

The resulting lead button is taken in the pincers, 
hammered free from slag, then cupelled, and the bullion 
bead is fused with silver-foil, parted, again fused with 
some more lead-foil, and again cupelled. The resulting 
button of pure gold can then be measured by Plattner's 
ivory scale. 

Two assays, or more, should be made, especially when 
assaying for gold, the "rich leads" being fused together, 
scorified (details of operation following), and cupelled as 
one. It is always advisable to scorify down, if possible, 
as there is less loss in silver, and the process is quicker 
than the cupellation. In a low-grade ore several separate 
charges should be fused down. Then scorify the pieces of 




32 FIELD TESTING FOR GOLD AND SILVER. 

silver-lead so obtained by twos and threes at a time down 

to small buttons. 

These small buttons are then scorified all together in 
a fresh cupel (or capsule), and the result- 
ing button is cupelled fine. In this way 
the silver and gold are united in one 
large button, the weight of which, as given 
on the scale, need only be divided by 
the number of charges taken to find the 
Fig. 42. amount of one charge. 

Scorifying. If the button is too large to cupel, it should 
be scorified down in the little capsule (Fig. 35). The 
capsule is placed on the top of the furnace or in the top 
of the pipe used for cupelling. First heat the capsule 
with the flame of the blow-pipe. Put in the cleaned 
lead button, or buttons, in the centre of the capsule, and 
blow down on it. First melt the lead beneath the full 
force of the reducing (yellow) flame, then keep the lead 
just melted beyond the blue tip of the flame. The lead 
rapidly oxidises. If too much copper or nickel is present, 
more lead is added. 

If a coat of oxide covers the lead, heat strongly with 
point of blue flame until it melts, and then process can 
go on steadily further away from point of flame. As 
process goes on, slag or litharge forms around bright lead 
button. This litharge is yellow unless copper present 
makes it black. If heat is too great, silver will be carried 
off, therefore it should be kept only hot enough to keep 
it from " freezing." 

When the lead is reduced to the size of a mustard seed, 
or in the case of a rich ore somewhat larger, the scorifier 
or capsule is gradually drawn away to let the bead cool 
slowly and prevent spurting and loss. If it does spurt, 



BLOW-PIPE ASSAY FOR GOLD. 33 

it shows the scorification has been carried too far, and the 
button with ejected silver is put in some sheet lead ready 
for the next process of cupellation. 

The lead silver button readily breaks away from the 
litharge on the anvil, and after being cleaned and squared 
is cupelled. 

Cupelling. The procedure of "cupelling" has already 
been alluded to, as also has the operation of "parting" 
or separating the silver and copper from the gold in the 
bullion, but a few further suggestions about it may be 
found useful. 

Parting. It will be remembered that before gold and 
silver can be "parted" by the nitric acid, some 2^ to 3 
of silver to 1 of gold must be present. 

Therefore it is best first to make a rough test of the 
ore by extracting a button on the cupel and see if it will 
" part." If it will not, a preliminary assay is made for 
silver (see example No. 3 under "Assaying with Field 
Furnace"). From the amount obtained a calculation is 
made of the number of assays necessary to obtain a 
quantity of silver so great that the gold may be parted 
from it ; and if the result of silver be required, and its 
weight exceeds that of the gold, enough separate assays 
can then be made to give the necessary preponderance 
of silver. 

As a rule, however, if the silver weight only approxi- 
mates that of the gold, it is usually hardly worth while 
calculating it, and silver-foil is added to the assay mixture 
(or to the bullion button obtained afterwards), to an 
amount necessary for parting. 

When working with this small amount of ore it is 

C 



34 FIELD TESTING FOR GOLD AND SILVER. 

recommended by Fletcher always to make at least three 
assays of an ore for gold, concentrating the rich leads 
together and cupelling in one button. Therefore, if the 
ore is low-grade, or if the preponderance of silver is 
desired for parting, and several separate assays are made, 
the fine cupellation of the raw lead from each assay is 
not performed separately, but as follows : 

When all the assays have been fused, and the lead 
freed from slag, and hammered into cubes, these are 
placed two or three at a time (if not too heavy), on a well- 
heated capsule (Fig. 35), and scorification conducted as 
described on p. 32. 

The resulting lead buttons are next put together in a 
new capsule (after they have been broken out, hammered, 
and cleaned), and the concentration by scorification con- 
tinued until the rich lead is only the size of a grain of 
mustard seed. This button is then subjected to a fine 
cupellation on another cupel. 

If the silver is to be determined as well as the gold, 
the button must always be large enough to weigh, which 
is now done on balance (Fig. 44), and the button is then 
parted by dissolving out the silver with nitric acid. The 
gold (pure) is then washed, dried, annealed (p. 25), and 
weighed or brushed on to lead-foil, fused, cupelled and 
measured on ivory scale, all operations having been 
already described. 

Result. We will again take the example given above (as 
a result from a free-milling ore), whose concentrates have 
now been tested quantitatively, viz., 3 grains of concen- 
trates, after roasting have been smelted in the Fletcher 
furnace. The resulting gold (pure) bead fitted in between 
the divergent lines of the ivory scale opposite cross-line 



BLOW-PIPE ASSAY FOR GOLD. 



35 



No. 7, Table A, giving a yield of 315 oz. to the ton. The 
value of pure gold being $20'67 per oz., we have a value of 
$6511 per ton of concentrates ; or since it took 128 tons 

of ore to yield a ton of concentrates, we have - =*50 

of a dollar (viz., 50 cents) as the yield of a ton of ore 
through its concentrates. Therefore the complete yield 
of the ore, already given as an example of a result under 
" Pan-amalgamation," will be 



COMPLETE RESULT. 
Free Gold 

Button of bullion was yellow, and weighed 
11 grain, at $18 an ounce (18 x 2 x 11) = 



$39-60 



Concentrates 
2 Ibs. yielded J oz. Therefore, 

(32 divided by | = 128) it takes 128 tons of 
ore to yield a ton of concentrates. Yield 
of concentrates, estimated on Plattner's 
ivory scale, is $6511. Therefore value 
per ton of ore from concentrates (6511 
divided by 128)= 



0'50 



Total value of gold per ton = 



- $4010 



A fire assay of this ore yielded a value of gold of $41*33 
per ton. 



FIELD TESTING FOR GOLD AND SILVER. 



USE OF IVORY SCALE. 

TABLE A. 

Showing the number of ounces of gold and silver per 
ton the ore carries when the gold and silver buttons cor- 
respond to the different numbered cross-lines on the ivory 
scale (Fig. 33), 3 grains of ore being taken for assay. 



No. of 
Cross- 
Line. 


Ounces of 
Gold per Ton. 


Ounces of 
Silver perTon 


No. of 
Cross- 
Line. 


Ounces of 
Gold per Ton. 


Ounces of 
Silver perTon 


50 




522-1 


25 


141-93 


64-5 


49 




490-6 


24 


125-72 


57-0 


48 


... 


460-6 


23 


110-57 


49-5 


47 


... 


433-5 


22 


96-77 


43-5 


46 


... 


405-0 


21 


84-16 


37-5 


45 


... 


379-5 


20 


72-76 


33-0 


44 




355-5 


19 


62-41 


28-5 


43 




331-5 


18 


52-96 


24-0 


42 




309 '0 


17 


44-7 


19-5 


41 




286-5 


16 


37-2 


16-5 


40 




267-0 


15 


30-75 


13-5 


39 


... 


247-5 


14 


24-9 


10-5 


38 




228-0 


13 


19-95 


9-0 


37 




211-5 


12 


15-75 


6-0 


36 




193-5 


11 


12-15 


4-5 


35 




178-5 


10 


9-15 


4-0 


34 




163-5 


9 


6-6 


3-0 


33 




150-0 


8 


4-65 


2-1 


32 




136-5 


7 


3-15 


1-3 


31 


... 


123-0 


6 


1-95 


9 


30 


... 


112-5 


5 


1-2 


45 


29 




100-5 


4 


58 


25 


28 




91-5 


3 


24 


1 


27 




81-0 


2 


07 


03 


26 




72-0 


1 


009 


003 



It is not necessary to be confined to the use of 3 grains 
of ore when calculating results by measuring beads on 
he ivory scale, therefore it will be advisable to explain 
what the ivory scale is made for, and how to use it with 
varvine Quantities of ore. 



ASSAY FOR GOtD. 



Two lines diverge from a point to 1 millimetre apart in 
a distance of 156 millimetres. This distance is divided 
by 50 cross-lines. The weight (in milligrams) of buttons 
of gold and silver respectively have been determined as 
they fit in between the diverging lines opposite to the 
cross-lines which divide the scale. The following Table B 
gives these weights : 

TABLE B. 

Weight of gold and silver buttons in milligrams cor- 
responding to the cross-lines on ivory scale (Fig. 33). 



No. of 
Cross- 
Line. 


Weight of Gold 
(pure) Button. 


Weight of 
Silver Button. 


No. of 
Cross- 
Line. 


Weight of Gold 
(pure) Button. 


Weight of 
Silver Button 


50 




3-48 


25 


946 


43 


49 




3-27 


24 


838 


38 


48 




3-07 


23 


737 


33 


47 




2-89 


22 


645 


29 


46 




2-70 


21 


561 


25 


45 




2-53 


20 


485 


22 


44 




2-37 


19 


416 


19 


43 




2-21 


18 


353 


16 


42 




2-06 


17 


298 


13 


41 




1-91 


16 


248 


11 


40 




1-78 


15 


205 


09 


39 




1-65 


14 


166 


07 


38 




1-52 


13 


133 


06 


37 




1-41 


12 


105 


04 


36 




1-29 


11 


081 


03 


35 




1-19 


10 


061 


027 


34 




1-09 


9 


044 


020 


33 




1-00 


8 


031 


014 


32 




91 


7 


021 


008 


31 




82 


6 


013 


006 


30 




75 


5 


008 


003 


29 




67 


4 


0039 


0017 


28 




61 


3 


0016 


0007 


27 




54 


2 


0005 


0002 


26 


1-065 


48 


1 


00006 


00002 



38 FIELD TESTING FOR GOLD AND SILVER. 

Thus we see that the weight of a gold button fitting in 
between the lines opposite cross-line No. 15 is 0'205 
milligrams, and of a silver button 0'09 milligrams. 

The procedure of determining the weight of 
a button by measurement on the ivory scale is 
to take it up with the slightly moistened point 
of the small blade of a penknife and place it 
between the two convergent lines. With the 
aid of a magnifying glass the button is seen 
more plainly, and it is then moved with the 
knife-point into a position where the lines are 
just tangent to its sides, the eye being held 
vertically over it. 

Should the button come about midway between 
two of the transverse lines, the percentage is 
found by simply dividing the sum of the per- 
centages corresponding to these lines by two. 

Should it, however, lie nearer one line than 
the other, the space between the lines may be 
divided into thirds by the eye, and if the button 
lies in the lower third, add one-third to the 
percentage corresponding to the lower line, or 
if in the upper third, subtract one-third from 
the percentage indicated by the upper line. 

It has been found that with ores containing 
less than 0*5 per cent., the weight of a single 
button can be more correctly determined on the 
ivory scale, and for ores over 1 per cent, the 
weight of a single button can be more correctly 
Fig. 33. determined by weighing than by measuring. 
The results obtained in measuring may be con- 
trolled by determining the weight of several buttons by 
measurement and then actually weighing them all at one 



ASSAY FOR GOLD. 39 

time, after thoroughly cleaning them between moist paper 
and the anvil. 

To calculate the yield of any ore per ton, it is necessary 
first to explain that 450*1 grains bears the same ratio to 
1 milligram that 1 oz. bears to a ton of 2,000 Ibs. There- 
fore if 4501 grains (called an "assay ton") of material 
are taken, the yield from it in milligrams is the same as 
the number of ounces in a ton of 2,000 Ibs. of the same 
material. 

So that if we take an "assay ton" (or a decimal of 
an assay ton) of ore or concentrates, the weight of the 
resulting button in milligrams will be the number of 
ounces (or decimal of an ounce) of gold or silver in a ton 
of the ore or concentrates. 

For convenience I have given Table A above (from 
Fletcher), where a small amount of ore or concentrates is 
taken, namely, 3 grains, However, any amount of material 
may be estimated by this ivory scale, the procedure 
being as follows : 

Suppose 10 grains of material are taken. There are 
as already mentioned, 450*1 grains in an assay ton, and 
this amount being divided by the number of grains of 

material taken, gives a figure ' = 45*01), which must 

be multiplied by the figure of the cross-line opposite which 
it fits in on the scale, that is to say, by the weight of the 
button in milligrams. The result will be the number of 
ounces to the ton (2,000 Ibs.) of ore. 

Thus if the button fits opposite cross-line No. 6. If it is 
silver we see *006 is recorded opposite cross-line No. 6 for 
silver in Table B, and we multiply this by 45*01 (see 
above), which gives the number of milligrams which an 
assay ton would yield, viz., "27006 oz. of silver per ton 



40 FIELD TESTING FOR COLD AND SILVER. 

of material taken. In the case of the button being 
a gold (pure) button, then we note that opposite No. 6 
on the gold scale there is a weight of '013 milligrams, 
and this multiplied by 45'01 gives '585 as the number of 
ounces of gold per ton in the material taken. 

If a larger pot than usual is used, as in a small field fur- 
nace (Fig. 57), the same calculation will give results say 
'2 of an assay ton of material is operated on, we have 
(4501 x '2) = 90'02 grains. 

Then as above 45Q>1 = 5 

90-02 

This time we will say that the button fits opposite cross- 
line No. 20 on the ivory scale. Then as before, for silver, 
5 x '22 (silver scale No. 20) = I'lO oz. of silver per ton 
in the material taken. 

Or if a gold button, then as before 5 x *485 (gold scale 
No. 20) = 2'4 oz. of gold per ton in the material taken. 

That is to say, the rule will be 

If weight of ore in grains = a 

and weight of button on ivory scale = b 

Then - x b = weight in ounces of ore or concen- 
trates per ton of 2,000 Ibs. 

Namely, we get the weight of a button in milligrams 
from an assay-ton weight of the material, which is the 
same thing as the number of ounces in a ton (2,000 Ibs.) 
of it. It being a simple rule of three as follows : If a 
button weighs b milligrams from a weight of ore, what 
will a button weigh in milligrams from an " assay ton " 
(450'1 grains) of ore ? 

Where there is gold and silver, and the latter is to be 
determined as well as the former, the button had better 
be large enough to weigh, and then, after parting, the 



BLOW-PIPE ASSAY FOR GOLD. 41 

ivory scale will indicate the weight of the gold button. 
This weight can then be deducted from the original 
weight, giving thereby the weight of silver by difference. 

Those gold buttons which are larger than cross-line 
No. 26 are more accurately determined by weighing on 
the balance, the procedure of which is given under 
"Assaying" further on, therefore Table B above only 
gives weight of the gold beads to that number. 

Measuring Gold Buttons larger than Cross-line No. 
26 on Ivory Scale. However, where it is desired to 
measure buttons larger than cross-line No. 26, and ascer- 
taining their weight thereby, it can be done as follows : 
As already mentioned, the scale diverges 1 millimetre 
in 156 millimetres, and is usually divided into 50 divisions 
in this span, there therefore being 3*12 millimetres between 
each division. 

The weight of the gold buttons are given up to cross- 
line No. 26, as it is better to weigh them if possible when 
larger than that. 

The weight of larger buttons can be calculated from 
the weight of these given in Table B, as follows : 
N = weight of gold button you wish. 
R = weight of a known gold button. 
Y= distances on scale from where the two lines 
come together (marked 0) to the cross-line 
corresponding to the unknown button. 
S = distance on scale from to the cross-line corre- 
sponding to the known button. 

Then N = A X Y 3 , 
S 3 

For example, we know from Table B that weight of gold 
button opposite cross-line No. 10 is "061 milligrams (R). 



42 FIELD TESTING FOR GOLD AND SILVER. 

The unknown button corresponds to line No. 35, viz., it 
is (35x3*12) = 109*2 millimetres from (Y). 

The distance on scale from to 10 (10x3*12) is 31*2 
millimetres (S). 

Then by above formula 



2*610 milligrams is the weight of a gold button opposite 
to cross-line No. 35. 

Estimating " Refractory" Values by Difference. It is 
evident that if estimations of the ore are made in the first 
instance by a blow-pipe assay, and then a pan-amalgama- 
tion test is made of the ore, and the free-milling value 
obtained thereby, that by difference we have the refractory 
values of the ore in question. 

Without going into the details, a sample of ore gave 
an average value, from three assays, of $79*28 per ton, 
and two pan-amalgamation tests gave an average yield of 
$21 '10 per ton. Therefore the difference, $59*18, may be 
considered as the refractory values of a ton of this ore. 

Namely 

Free-milling value - - $20*10 per ton. 
Refractory value - - 59*18 

Total - - $79*28 



BLOW-PIPE ASSAYS FOR SILVER. 43 

BLOW-PIPE AND PAN-AMALGAMATION 
ASSAYS FOR SILVER. 

Qualitative Estimation. For silver ore, the prospector 
can, by use of the blow-pipe, roughly determine whether 
galena, or decomposed carbonates, carry enough silver 
to make them worthy of assay. In some cases it will be 
better to pan down and test the concentrates. If much 
sulphurets, or arsenic or antimony, is present, the ore 
must first be carefully calcined in a little clay capsule 
(Fig. 35). 

In the same manner as above mentioned for treatment 
of gold concentrates, the silver ore can be scorified, or 
mixed with litharge, borax, soda, and flour, fused down, 
and the resulting lead button cupelled. A silver button 
is obtained if the metal is present, and if silver alone, it 
will all dissolve in nitric acid. 

Lead ore will be more safely valued for its silver con- 
tents alone, viewing lead as a by-product, therefore this 
test is of value to the prospector. 

Quantitative Estimation. In exactly the same manner 
as for gold, the silver button, obtained from a weighed 
quantity of pulp, can be measured on the Plattner ivory 
scale, and with a greater degree of correctness than the 
gold button, owing to its larger size. For flux, the same mix- 
ture asabove mentioned under gold maybe used (pp. 29, 30), 
but for galena use 8 grains of ore, 4 grains of soda, 6 grains 
of nitre, and a salt cover. (In this case multiply weight 
of the button in milligrams, as shown by the Plattner ivory 
scale, by 56'26 to get ounces per ton of silver in ore.*) 

The resulting lead button should be first scorified in a 

* See p. 39 for reason. 



44 MELD TESTING FOR GOLD AND SILVER. 

little clay capsule to oxidise off the lead, as there is less 
loss to silver this way than in cupellation. 

When small enough the lead button is broken out. It 
breaks out very cleanly from the capsule, and is then 
cupelled and measured on ivory scale. 

If 3 grains of pulp are taken, the result is shown on 
Table A, or if more ore be operated on, the result is 

calculated from Table B, and the formula x , given 

under " Use of Ivory Scale" above. 

Thus, if 10 grains of ore were smelted, and silver button 

450 1 
fitted opposite cross-line No. 22 ('29 milligram), then - 

x *29 equals 13 oz. of silver to the ton. 

Or if the button be" large and be weighed, this is done, 
and the value arrived at, as described under "Assay with 
Field Furnace," just following this. 

If the ore is rich, it can be determined by scorifica- 
tion by mixing 3 grains of pulp with 15 grains of lead 
and a small piece of borax glass, proceeding exactly 
as under " Scorification " (p. 32) and k ' Cupellation " 
(p. 33), already described in gold assay. 

The general tendency is to cupel too hot. This makes 
process longer and causes a loss in silver (pp. 22 and 106). 

Other mixtures and other tests can be seen in the 
excellent little blow-pipe work by Fletcher, published by 
John Wiley & Sons, 53 Tenth Street, New York, U.S.A. 

An approximate quantitative field test by pan-amalga- 
mation can be made of silver ores which do not contain 
too much lead. 

The procedure is somewhat similar to that of gold ore, 
except that the stirring in the pan is in this case grinding 
with a stone, flat on the grinding side. One ounce of salt 



TESTING CONCENTRATED ORES. 45 

is added, and the pulp is ground for an hour. The pan is 
then heated, and ^ oz. of copper sulphate is added, and 
stirred for a little while ; then an oz. of mercury is added 
and the grinding is continued for an hour or longer, 
occasionally warming the pan. The mercury is then 
panned out and retorted and weighed, as in the case of 
the gold ore. 

If the ore is "rebellious," with much sulphurets or 
arsenic or antimony, it will be necessary to previously 
roast the pulp until the fumes are nearly all driven off, 
then add salt, mix well, and finish roasting at a good heat. 

The ingredients mentioned above (copper sulphate and 
extra supply of salt) are not included in list of " outfit," 
because the blow-pipe "smelting" process will be found 
much more convenient, as a rule, for silver ores. 



TESTING CONCENTRATED ORES. 

Gravels, gold ores, or silver ores can all be concentrated 
by panning, and then tested as above, the result being 
divided proportionately to the amount taken. This is a 
matter of common-sense. For example, if 10 Ibs. are 
panned down to 1 Ib. and that is tested, the result 
would be divided by 10 to give the yield of the original. 

Some judgment must be used in the class of ore so con- 
centrated. If it was a smelting ore, the loss in sliming 
in the brittle sulphurets or tellurides would give a yield 
altogether below the real value of the ore. The same 
result would also be found to obtain in the case of a gold 
ore where there was much fine gold, for some of it will be 
amalgamated in a stamp mill, while in the previous con- 
centration of the ore a larger proportion will be washed 



46 FIELD TESTING FOR GOLD AND SILVER. 

away. Conditions must govern cases, but, generally 
speaking, gravels and extremely low-grade ores only 
should be tested after being concentrated. 

Where testing concentrated ore, the direct formula to 
calculate the result from will be 

The weight in grains of the ore before concentra- 
tion = A. 

Weight in grains of concentrated portion = B. 

Weight (in milligrams) of gold (pure) button from 
assay =C. 

Number of grains of concentrates taken for assay = D. 

A 

=E = number of assay tons of ore taken. 

' -xC 

Then E = ounces of gold, or silver, which the ore 

~D~~ 

carries to the ton of 2,000 Ibs. 



BLOW-PIPE ASSAY OUTFIT. 

24 A. Black's blow-pipe, large nozzle. 

33. Plattner's ivory button scale. 

34. Clay crucibles, one dozen. 

35. Clay capsules, two dozen. 

36. Fletcher's blow-pipe furnace, with side hole. 

37. Camel hair brush. 

38. Flour, J oz. in tin box. 

39. Methylated spirits, J pint. 

40. Common salt, fine, \ oz. in tin box. 

41. Nitre, J oz. in tin box. 

42. Spirit lamp, tin. 

43. Blast-bulb. 



BLOW-PIPE ASSAY OUTFIT. 



47 



With the above-mentioned complete outfit (Nos. 1-43) 
free-milling ores can be tested, and value determined as 
low as $1*50 per ton for gold ores, and much lower, if 
desired, for silver ores. Also the value of the concen- 
trates, of refractory gold ores, or of smelting silver ores, 




Fig. Y. 



can be approximately estimated. Any one can learn pro- 
cess of testing with this outfit in a few days. As it is 
portable and exact in its results (especially for free-milling 
ores), this outfit should prove of value to prospectors, or 
experts, in the field. 

The weight of the outfit (Nos. 1-43) is about 20 Ibs, 



48 FIELD TESTING FOR GOLD AND SILVER. 



COMPLETE PAN-AMALGAMATION AND 
BLOW-PIPE ASSAY OUTFIT. 

The articles already named, from 1 to 43 (pp. 27, 28, 
and 46), constitute the above-mentioned complete outfit. 
These may all be carried in a convenient little box, such 
as represented in Fig. Y, with the exception of the larger 
and stronger articles, such as mortar and pestle, pans, 
mixing cloth, and sieve. The box may be of dimensions 
14 inches long, 8 inches wide, and 4 inches high, which 
will conveniently pack away in any prospector's pack- 
sack. 



ASSAYING WITH FIELD FURNACE. 



49 



ASSAYING WITH FIELD FURNACE. 

For field-testing work on gold and silver ores, pan- 
amalgamation and the blow-pipe will, if persisted in, give 
as approximate a value of the ore as to justify subsequent 
work on the claim or its 
abandonment. There are 
many instances, however, 
where, in the blow -pipe or 
smelting process, it is of great 
advantage to operate on a 
much larger quantity of the 
material at one time. 

This can be done by means 
of a portable assay furnace, 
using preferably some form 
of gaseous fuel. 

The smallest and most 
portable furnace (Fig. 57) 
which has come under my 
notice is made by E. H. 
Sargent & Son, of Chicago, 
Illinois. This furnace has the 
advantages of only weighing 
7 Ibs., being about 5 by 8 
inches, when set up it is about 
20 inches in height, and it 
packs in a space of 1 cubic 
foot, with all the necessary Fig. 57. 

materials the box then 

weighs, ready packed, some 25 Ibs. (without mortar and 
pestle) ; and lastly, one of its greatest recommendations 
is that refined petroleum (" coal-oil ") is used as 1 the fuel. 




50 FIELD TESTING FOR GOLD AND SILVER. 

This form of fuel is much more easily obtained, and is 
less dangerous, than gasoline, which is the volatile liquid 
fuel most commonly used for assaying. 

General Procedure. The procedure for assaying gold 
and silver is quite simple. The main features have 
already been alluded to under the blow-pipe assay. As 
in that operation, the process consists in a fusion of a 
mixture of the ore with fluxes, or by scorifying the ore with 
lead and borax where it is of a high grade. The fluxes 
are arranged so that metallic lead is liberated, which seizes 
hold of any gold and silver present, while the quartz, 
silicates, iron 4 etc., which may be in the ore, are carried 
off as slag. 

If an ore contains much sulphide it is always best to 
roast it previous to a crucible assay, and add an iron nail 
or two, which combines with the sulphur. 

As previously mentioned under the blow-pipe work, the 
ordinary quartzose gold ores are fluxed principally by 
sodium bi-carbonate, to combine with the silica. Litharge 
will take up the silica, and can be used where the pot is 
small and fear of boiling over is felt, which occurs some- 
times with the soda. Care must be taken, however, that 
the excess of litharge is not enough to eat into the crucible. 
For roasted concentrates, or limy silver ores, borax is 
used, and silica (pulverised glass, etc.) is added to flux 
the iron or lime and protect the crucible. 

These are the general principles which it is well 
to keep in mind, and as ores are generally mixtures, 
they require a corresponding mixture of fluxes to treat 
them. 

In the following procedure I do not pretend to 
go into the many details which are required in labora- 



ASSAYING WITH FIELD FURNACE. 5! 

tory assay work, to meet all the difficulties that may be 
met with in treating complex ores ; therefore if much 
assaying is contemplated, I would recommend the 
reader to get Brown's "Manual of Assaying," or some 
similar work. 

The procedure mentioned hereafter is with a view of 
the operator using some originality, and in all probability 
improving on the suggested methods. 

Sampling and " Metallics." We will consider that the 
process of obtaining a fair average sample has been gone 
through as laid down under the preliminary procedure 
for "pan-amalgamation" (pp. 10-13). 

The resulting pulp after having been quartered down 
the last time, and put aside for the assay sample, is then 
run through a 60 or 80 sieve, the portion not running 
through being further pulverised in the mortar until 
nothing but flattened "metallics," or particles of wood, 
etc., remain on the screen. These latter are dumped on 
a piece of paper, and as before mentioned, treated by a 
magnet, which takes off any iron, while any pieces of 
wood, etc., are blown off by a gentle breath. 

If there are any malleable flakes of gold or silver 
("metallics"), they are carefully brushed on to a small 
sheet of lead, which is folded over on them and made 
into a little ball. This is fused, fluxed with borax glass, 
cupelled, and estimated as mentioned hereafter for the 
resulting button of the assay proper. 

If there are "metallics," which must be treated as 
above, the whole of the sieved pulp from which they 
have come is weighed, and the proportionate yield of an 
assay ton of this pulp in "metallics" may be estimated 
as follows : 



52 FIELD TESTING FOR GOLD AND SILVER. 

We will suppose that there are 6 oz. of pulp. There 
are 437'5 grains in an ounce (av.). 
437'5 x 6 = 2625 grains. 
There are 450'1 grains in an assay ton. 
Therefore 2625 -f- 450*1 = 5 '8 assay tons in sample. 
We will suppose that the resulting gold button from 
the "metallics" weighed 1*25 milligrams. Then 1'25 -*- 
5*8 = '21 as the weight of gold "metallics" from I assay 
ton of pulp. 

And as every milligram in the resulting gold button 
means an ounce of gold in a ton of the pulp this would 
be equivalent to a yield of '21 oz. of gold in "metallics" 
from a ton of the pulp. This will be added to the result 
obtained from the assay of the pulp. 



Fig. 48. 

i he same instructions will apply to silver, should there 
be metallic silver in the ore. 

Weighing-out Charge. We now have the 6 ozs. of 
pulp in a fine state of division from which "metallics" 
may, or may not, have been taken. This should be 
dumped on a piece of rubber cloth or glazed paper, and 
thoroughly mixed by rolling from each corner (as already 
described in the large scale sampling), and by turning 
over and mixing with a spatula (Fig. 48) or common 
kitchen knife (which is very useful). 

The sample can then be quartered down, and the two 
discarded quarters brushed off, the remainder mixed again, 
and if it is still a larger sample than 3 or 4 oz. it can be 
again quartered down. Then it is carefully flattened down, 



ASSAYING WITH FIELD FURNACE. 53 

and the assay is taken from it in little portions from every 
part of the flattened pile, taking care to get some of the 
bottom as well as the top, and from the edges as well as 
the middle (this is more particularly described under 
"Charging" just below), the assay ton weights No. 45 
in list of outfit being used to weigh out the pulp. 

Scorification. We shall first consider the assay by 
scorification with the field furnace. 

Charging. The sifted ore, or pulp, is spread out J inch 
deep, and '1 assay ton is weighed out on the ore balance 
(Fig. 11), picking up a bit here and there from ^ 
a dozen or more places, with the small spatula l~^ if 
(Fig. 48). This weighed charge of ore is poured Fig> 46 
into a scorifier (Fig. 51), and the particles 
clinging to the scale pan are swept into it with the 
camel's hair brush (Fig. 37). 

The lead measure (deep cavity) Fig. 46 is next filled 
with test lead, and half of this is poured on the ore in the 
scorifier and well mixed with it, using the spatula f the 
second half of the lead is poured over 
this, and a borax measure (shallow 
cavity) of borax-glass added. (See 
also under " Blow-pipe Assay.") As a 
rule, 5 parts of lead to 1 of pulp will 
suffice, but where copper runs over 7 
per cent, or nickel over 10 per cent, more lead is necessary, 
as much as 15 of lead to 1 of ore. The same applies to 
matts and speiss. 

Starting the Blast and Scorifying. The reservoir is 
filled with kerosene to within f inch of the top, and the 
cap firmly screwed on. The cup is then filled with alcohol 
(wood-alcohol is cheap and good) and lighted. The 




54 FIELD TESTING FOR GOLD AND SILVER. 

furnace is placed on the support with the muffle in place 
and its door closed. As soon as the alcohol in the cup 
is seen to boil, a stroke or two of the pump is given (the 
air valve being of course closed) ; the outrushing vapour 
is kindled and the retort becomes hot. When the alcohol 
has burned out, more pressure is given with the pump, and 
as soon as the top of burner becomes red hot, full pres- 
sure, obtained initially by about 50 strokes of the pump. 

In a short time the inside of muffle grows bright red, 
when the charged scorifier is placed at the back of muffle 
with the tongs (Fig. 55), the door is closed and plugs 
inserted. A few minutes later, a glance through the vent- 
hole will show the lead melted and the ore floating on 
it. The door is then laid on its back (leaving the upper 




Fig. 55. 

half of the muffle opening exposed) and the assay allowed 
to take care of itself. The ore promptly sinks into the 
lead, the latter is oxidised, part of it passing off in fumes, 
and a much greater part floating to the sides in small 
flakes, where they form a ring of slag which constantly 
grows as the melted button of lead becomes smaller and 
smaller, till the slag closes over it, and the scorification 
is complete. The scorifier is then removed and allowed to 
cool, or it is poured out into a small iron mould. If it be 
placed on the anvil, the cooling will be much hastened. 

A few strokes of the pump must be given occasionally 
to keep up full pressure, and should the lead solidify or 
^freeze," half a measure of borax should be added and 



ASSAYING WITH FIELD FURNACE. 55 

the door closed to raise the heat in the muffle for a short 
time. 

When the scorifier has grown cold it is broken with 
the hammer, and the lead ( usually found in one button, 
though it is worth while crushing up the slag and looking 
through it for scattered lead) is beaten into a cube and 
thoroughly cleaned with the button brush. 

Smelting" in Pot. We shall now consider the work of 
weighing out the charges of pulp and fluxes for a fusion 
in a pot. It is best to have one set of weights for all 
purposes, and as it is much more convenient to have the 
assay ton weight for weighing the pulp, we shall use that 
weight, and its divisions, for the fluxes also. As already 
indicated, the weight of "assay ton" bears such a relation 
to the ton that when an assay ton of pulp is taken, for 
every milligram of weight in the gold or silver button 
resulting from the assay there is an ounce of that metal 
in the ton of pulp (or ore). 

The following mixture is weighed out on the little bone 
scales (Fig. 11), using the assay ton weights, and putting 
the sliding weight of the scales at 0. 

For Roasted Concentrates. For Ore. 

Ore "2 assay ton "2 assay ton. 

Litharge "3 *3 

Borax *3 T 

Soda *1 - *3 

Flour '05 - - '05 

This is fused in the furnace, the manipulation of which 
is as above described. When the fusion is complete, the 
charge is poured out into a small iron mould (No. 65), or 
the pot is allowed to cool and the bead is broken out. The 
lead button is then squared by hammering on the upturned 




56 FIELD TESTING FOR GOLD AND SILVER. 

iron mortar, holding it with the pincers (No. 27), and it is 
then ready for scorifying still smaller, or cupelling at once. 

Cupellation. Wipe out a cupel (Fig. 50) with the 
finger, place in muffle and get it very hot ; then put the 
cube of lead in it, either by sliding cube from large spatula 
or drawing cupel to front of muffle and placing cube in 
it with the tongs. Lay a bit of charcoal on cupel so as 
not to entirely cover the cavity and push to back of 
muffle ; close door, insert plugs, and raise 
heat till, by looking through vent at part 
of cupel cavity not covered by the charcoal, 
the lead is seen to be fluid, then remove 
Fig. 50. charcoal and close door, leaving plugs out. 
The lead oxidises as it did in the scorifica- 
tion process, but the little flakes of lead oxide, in place of 
collecting in a slag at the sides, are absorbed into the 
body of the cupel. Watch the lead as it grows very 
small, and as the last of it leaves the precious metals 
there is usually an interesting "flash" from the latter. 
Remove the cupel and place on anvil to cool. 

Inquarting. Unless the ore be known to contain no 
gold, it is well to inquart or alloy with silver at once, so 
that acid can get at and dissolve out the silver already 
alloyed with the gold ; more or less silver always is 
associated with gold in ore. Weigh out about three times 
as much silver-foil as the button weighs. Should the 
button be too small to weigh, the silver must be guessed 
at. It may be approximated by remembering that the 
foil weighs about 3'3 grains to the square inch, hence an 
eighth inch square weighs "05 grains, and a sixteenth 
inch a fourth as much. 

Having cut off with scissors the proper amount of 



ASSAYING WITH FIELD FURNACE. 57 

silver, as nearly as may be, place it in contact with the 
button in a little hollow made with a knife in a charcoal 
slab. Direct the flame of the spirit lamp with the blow-pipe 
on the metals for a moment and they will fuse together. 

Parting. Having separated the fused button from any 
clinging fragments of charcoal by rolling between the 
finger and thumb, it is placed in a perfectly clean porce- 
lain dish and a very few drops of pure (rain) water are 
.placed on it with the dropper (Fig. 54), then a drop or 
two of nitric acid is added, and the dish is warmed over 
the lamp till chemical action begins indicated by a 
multitude of small bubbles arising from the button. It 
is then put down till action ceases. Should the entire 
button be dissolved without residue, it shows that there 
is no gold in the ore ; but if there remain 
a black or very dark brown powder or mass, 
pour off the fluid very carefully, preferably p. ^ 
into another dish, so as to catch any of 
the residue that may be carried over. Three or four 
times add a few drops of water, each time heat, wash 
several times, decant the water, and finally heat the dish 
till it is entirely dry, and now weigh the pure gold. 
Should the amount be too small to weigh, make a small 
capsule of lead-foil, place the gold in it and pinch 
together so as to retain it, then cupel as before in the 
muffle or with the blow-pipe. The process is now a short 
one, there being so little lead to get rid of. When the 
cupel is cold, detach and measure the tiny button of gold. 
(See under " Use of Ivory Scale.") 

Weighing or Measuring. When cupel is cool, remove 
button with the forceps and place it in pan (depression) 
of button balance. Should it be too small to take hold of 



FIELD TESTING FOR GOLD AND SILVER. 



with forceps, detach with a touch of a knife's point, four 
it on to a piece of writing paper, and thence four it into 
balance pan or on to ivory scale. Weigh by trying the 
various riders at different positions. 

The button balance (Fig. 44) is a bar balanced on a 
knife edge. It is divided into ten parts, and the manner 
of weighing on it is by balancing riders of different 




Fig. 44. 

weights against the bead. There are three such riders 
weighing 100, 10, and 1 milligrams respectively. The 
following gives the weights of buttons indicated by them. 

TABLE C. 



No. of 
Division 
on arm of 
Balance. 


Light Rider 
(1 milligram) 
Weight of Button. 


Medium Rider 
(10 milligrams) 
Weight of Button. 


Heavy Rider 
(100 milligrams) 
Weight of Button. 


1 

2 


'1 milligram 
"2 


1 milligram 

2 


10 milligrams 
20 


3 


3 




3 




30 




4 


'4 




4 




40 




5 


5 




5 




50 




6 


6 




6 




60 




7 


"7 




7 




70 




8 


8 




8 




80 




9 


9 




9 




90 




10 


10 




10 




100 





To get the yield of the ore where '1 assay ton of 
material is taken, the weight of the button of gold, or 
silver, in milligrams (taken from above table) multiplied 



ASSAYING WITH FIELD FURNACE. 59 

by 10 will give the number of ounces per ton in the ore ; 
or if '2 assay ton of material is taken, the weight of the 
button in milligrams multiplied by 5 will give the number 
of ounces per ton in the ore ; or if *5 assay ton of material 
is used, the weight of the resulting button in milligrams is 
multiplied by 2 to get the number of ounces of gold or 
silver in a ton of pulp. 

Where a button is too small to weigh, it can be measured 
on the ivory scale, exactly as laid down under " Use 
of Ivory Scale." 

If a = fraction of assay ton of ore taken, and b weight 
of resulting button in milligrams, 

Then - x b weight of button from an assay ton of 
ore, or ounces of gold or silver in a ton of the pulp. 

EXAMPLE No. 1. WEIGHING. 

An unparted button, from *2 assay ton of ore, balarced 
the medium rider on line (or division) No. 2, and the 
light rider half-way between No. 6 and No. 7. It entirely 
dissolved in the nitric acid. 

Solution. Since it entirely dissolved, the ore contains 
no gold. 

To find the yield of silver, since the button was weighed 
(and not measured), refer to table of weights (Table C). 
Line No. 6, light rider, gives "6 milligrams. 
Line No. 7, light rider, gives '7 



The average being - - *65 
Line No. 2, medium rider, gives 2'00 

Then 2'65 x5 = 13'25 oz, 
is the amount of silver to the ton of 2,000 Ibs, 



60 FIELD TESTING FOR GOLD AND SILVER. 

EXAMPLE No. 2. MEASURING. 

If from '1 assay ton of ore a button of pure gold on 
ivory scale fits opposite cross-line No. 7 ('021 milligrams, 

Table B), we then have .y x '021 = 10 x '021 = '21 oz. of 
gold to the ton of 2,000 Ibs. 

Where the yield of both gold and silver is desired, the 
button must be large enough to weigh before parting. 
(See also " Blow-pipe Assay "). We will suppose that the 
button will part. Then we have an 

EXAMPLE No. 3. GOLD AND SILVER. 

The unparted button, from '2 assay ton of ore, balanced 
medium rider at 4 and light rider at 6. 

The gold button balanced light rider at 3. Refer to 
Table C. 

Line No. 4, medium rider, gives 4*0 milligrams. 
Line No. 6, light rider, gives 0'6 

Weight of button = 4'6 
Line No. 3, light rider, gives '3 of gold. 

There are therefore 4'3 of silver. 
As there were *2 assay ton of pulp, 1 -r '2 = 5, and we 
have as result 

'3x5= 1-5 oz. of gold ) 
4-3x5 = 21-5 oz. of silver} 10 the ton f Ore ' 
It is hardly necessary to remark that the resulting gold 
button can be measured if too small to weigh. 

If "metallics" are encountered in the preparation of 
the sample, they are treated separately as another assay, 
and their value added to that of the result of the assay 
whether in gold or silver, or both. The estimation of 



ASSAYING OUTFIT. 



61 



" metallics " has been treated under the head of " Sam- 
pling and Metallics "(p. 51). 

Notes. It is customary to assay test and sheet lead 
and litharge for silver, and make allowance for the amount 
of this metal ; lead always containing more or less silver. 

Occasionally the lead will " freeze " in the cupel. The 
remedy is to add lead-foil, introduce a piece of charcoal 
(as at starting), and raise the heat. 

Should scorifier or cupel spill on muffle, at once place 



Fig. 56. 

bone-ash (the white or unsaturated part of used cupels 
may be crushed and saved for the purpose) on the spill^ 
stir and rake out with scraper (Fig. 56). 



ASSAYING OUTFIT. 



44. Button balance, with 

three riders. 

45. Weights '05, '1, '2, 

and '5 of an assay ton. 

46. Lead and borax mea- 

sure. 

47. Small sheet rubber 

cloth, 9 inches square. 

48. Common kitchen knife 

or spatula. 

49. Small varnishing brush. 



50. Cupels, 6 dozen. 

51. Scorifiers, 4 dozen. 

52. Pots, 2 dozen. 

53. Button pincers. 

54. Medicine dropper. 

55. Scorifier tongs. 

56. Rake. 

57. Blast lamp, support, fur- 

nace, nipple, cleaner, 
muffle, door, and plugs. 

58. Test lead (granulated). 



62 FIELD TESTING FOR GOLD AND SILVER. 



59. Litharge. 

60. Borax glass. 

61. Soda. 

62. Salt. 

63. Hammer, large, for ore. 



64. Scissors. 

65. Small iron mould. 

66. Button brush. 

67. Cupel and lead-button 

tongs. 



This part (44-67) of the complete outfit (1-67) is 
supposed to be augmented by a few necessary articles 
already enumerated in the previous lists (pp. 27, 28, 46). 

ASSAY OF TELLURIDE GOLD AND 
SILVER ORE. 

SCORIFICATION ASSAY. MIXTURE FOR POT ASSAY. 

Assay Ton. Assay Ton. 

Ore - - - 01 Ore - - 0'2 

Litharge - - 1*0 (cover). Soda bicarb. TO 

Granulated lead 2*0 Litharge - 2*0 

Borax glass cover. Argol - -01 

Borax glass cover. 

The above charges are recommended by Mr F. Clemes 
Smith in a paper in Trans. Am. Inst. M.E.^ and are said 
to minimise the loss of gold. 

TESTS BY CHLORINE AND CYANIDE. 

Refractory ores are treated by smelting or chlorination ; 
or, when the gold is very finely divided, by cyanide solu- 
tion. Assaying as already described will give value of 
ores, but it is often desirable to determine by an actual 
test the values which can be extracted by chlorination or 
by the cyanide process. With this in view the following 
general notes of procedure are given to form the basis of 
tests in which the operator can use ingenuity as to apparatus 
and manipulation.* 

* The following tests will scarcely be within the range of the 
prospector, but they have been inserted for the convenience of 
engineers in the field. 



ASSAY BY CHLORINATION. 63 

Assay by Chlorination. Sulphide ores (if not roasted), 
and ores with calcite, dolomite, and manganese, are not 
adapted for chlorination, as they use up too much chlorine. 
The test is carried on as follows : Place the completely 
roasted sample in an ordinary soda-water bottle with 
enough water to make the whole of the consistency of 
thin mud. The ore and water should together occupy 
about two-thirds of the bottle. Bleaching powder and a 
thin glass bulb filled with dilute sulphuric acid are then 
added, and the bottle securely closed. As cork is attacked 
by chlorine, glass or vulcanite stoppers are better, and the 
screw-stoppered bottles are most convenient. If corks 
are used, they must be wired down. The bottle is then 
shaken so as to break the sulphuric acid bulb and mix its 
contents with the bleaching powder, when chlorine is 
evolved. The bottle is now left for several hours in a 
warm place, being shaken occasionally by hand to mix its 
contents. At the end of a period of eight to twelve hours 
the bottle is opened, and if excess of chlorine is still pre- 
sent the liquid is separated from the ore and the latter 
washed thoroughly by filtration or decantation. The 
liquid and washings, whether clear or muddy, are warmed 
to expel free chlorine, and an excess of ferrous sulphate is 
then added to them. The precipitate is collected, scori- 
fied with lead, and cupelled. In all cases it is better to 
keep the first liquid separate from the washings, which 
should be concentrated by evaporation, since if this is not 
done the precipitate of gold may be too fine to settle and 
will pass through filter paper. A better method of precipi- 
tation is to boil the liquid with iron filings for a few 
minutes, decant through filter-paper, wash the filings, 
and dissolve them in dilute sulphuric acid, when a 
residue of gold is obtained which is easy to filter. 



64 FIELD TESTING FOR GOLD AND SILVER. 

Bromine may be used instead of the materials generating 
chlorine. 

The quantities of chemicals required will be such as 
are sufficient to generate a volume of chlorine equal to 
twice the capacity of the bottle used, or a solution of 2 
per cent, of bromine in water works well. 

Assay by Cyanide. Ores that contain much ferrous 
salts or copper salts (particularly oxidised ores, carbonates, 
etc.) are not well adapted for the cyanide process, as they 
consume a great deal of potassium cyanide and therefore 
make the process expensive. 

In the first place, two standard solutions are necessary to 
carry on this test : (1) A standard solution of caustic soda, 
which is made by dissolving 40 grains of the caustic soda in 
1 litre of water, which solution will give '04 grain of caustic 
soda to every cubic centimetre of the solution this is used 
to determine the acid (or cyanide wasting) properties of the 
ore ; (2) a standard solution of silver nitrate, which has 
170 grains of silver nitrate in 1 litre of water this is used 
to estimate the amount of potassium cyanide present. 

The process of testing is as follows : * 400 grains of 
ore are mixed with water, then every cubic centimetre of 
caustic soda that is added will represent O'Ol per cent, of 
caustic soda as necessary to neutralise the ore.t For an 
example, suppose it took 24 cubic centimetres of standard 
solution before the litmus paper showed blue (viz., before 
neutralisation), therefore 0*24 per cent, caustic soda is 

* First steep some of the pulp for ten minutes in an equal volume 
of water, and if it does not turn blue litmus paper red dispense 
with caustic soda test, and go directly into cyanide consumption 
estimation. 

t A second soda test can be made after the ore has been washed 
by water. The difference in the result will show the amount of 
soda which may bs saved. 



ASSAY BY CYANIDE. 65 

necessary to neutralise the ore, or 100 tons of ore will 
take "24 of a ton (viz., 480 Ibs.) of caustic soda to 
neutralise it. 

The next test is made to see how much cyanide is used up. 
Five hundred grains of the ore are taken in 500 grains of 
water. Twice the theoretical amount of caustic soda is then 
added to the ore in this solution. Shake up for half an hour 
so that all the free acid and acid salts are neutralised. Add 
500 grains of 1 per cent, solution of potassium cyanide, 
which brings it to J per cent, solution, as there are already 
500 grains of water to which it has been added. Shake 
up for ten minutes. This is filtered and tested by the 
above-mentioned silver nitrate solution, and every cubic 
centimetre of this is equivalent to a consumption of '13 
grains of potassium cyanide. 

Then 1,000 grains of the ore are taken and mixed with 
1,000 grains of J per cent, potassium cyanide in a bottle, 
and either agitated on a water-wheel for from twelve to 
twenty-four hours or allowed to stand the same time. 
Another lot of 500 grains can be taken with 1,000 grains 
of J per cent, solution, and treated in the same way. The 
product is filtered, and 500 grains of the filtrate is evapo- 
rated nearly to dryness. Then carbonate of soda, some 
glass, borax, litharge, and flour are added for an assay, 
and it is smelted. The resulting button is weighed, and 
the result calculated as from 1,000 grains of ore in the 
one case or 500 grains of ore in the other case. 

The estimation is sometimes made by difference, viz., 
assaying the ore, then dissolving out with cyanide, and 
assaying the tailings after they have been well washed ; 
the difference giving the amount that the cyanide has 
dissolved out. 

The strength of solutions of cyanide in practice vary 
rom *3 oer cent, to '08 oer cent. 



66 FIELD TESTING FOR GOLD AND SILVER. 



PROSPECTOR'S OUTFIT. 

When a prospector is going out into the woods or into 
the mountains to prospect, he does it in one of two ways. 
Where there are many lakes, he takes his outfit in a canoe. 
In the mountains he takes his outfit on a horse. In either 
of these cases his camp is a centre, and he moves every- 
thing with him from camping place to camping place, 
and sleeps there every night. 

In these cases he takes his whole testing outfit, as 
above enumerated, as its total weight is only about 20 Ibs., 
including pans, mortar, c., or 50 Ibs. with field furnace. 

In the other way of prospecting, the prospector goes 
off with a very light outfit on his back, and he camps 
where night overtakes him. In such a case a prospector's 
outfit for a month may be somewhat as follows : 

A compass. 

A magnifying glass. 

A map of country (geological if obtainable). 

A note-book and pencil. 

One pair of blankets. 

Small tent, 2 or 3 Ibs. 

25 Ibs. flour. 

1 Ib. tea. 

One small hand axe. 

One poll-pick (heavy). 

5 Ibs. bacon (more is necessary if no prospect of 

game). 
Two tin plates, cup, a small tin tea-pail, a hunting 

knife. 




PROSPECTORS IN A CANOE. 



{To face p. 66, 



PROSPECTOR'S OUTFIT. 67 

Some matches, salt, soap, and towel. 
Horn for panning (Fig. X). 

22 single shot rifle (short, long, and extra long 
cartridges). 

The rifle alluded to can either be used with a short 
cartridge to shoot birds, rabbits, etc., or it will kill deer 
with the extra long cartridge ; therefore the rifle means fresh 
meat to the prospector. In starting out his pack weighs 
about 50 Ibs., coming back it will weigh some 16 Ibs. 

Some oatmeal may advantageously be substituted for 
part of the flour for the evening meal. 

If the prospector can stand the weight, he will pro- 
bably add sugar, but every ounce counts. 

With this light outfit the prospector, after locating some 
place, will come back to it with a larger outfit and more 
food, and do his work of opening the claim to see what it 
is like. All the testing he can do with this outfit is to 
crush up any ore he finds on a rock with his poll-pick 
and pan it with his horn. He can easily take enough of 
his testing outfit in his pocket to test the concentrates 
with blow-pipe and cupellation. If he has no horn he 
will use a plate for panning, after burning off the grease. 

If the prospector is in a placer country, he will substi- 
tute a light shovel and a pan for the poll-pick and horn. 

In the first-mentioned case, where a prospector has 
a canoe or pack horse, in addition to things above 
mentioned, he will have a larger " A " tent, a shovel, the 
outfit for testing, above enumerated, or at least a pan, a 
mortar and pestle and a sieve, a frying pan, some sugar, 
beans, bacon, and a larger supply of eatables generally. 



68 FIELD TESTING FOR GOLD AND SILVER. 



USEFUL INFORMATION. 

A ton of broken quartz measures about 20 cubic feet. 

The area of a circle is 07854 (diameter) 2 . 

Ratio of area to circumference is as its radius is to 2. 

An acre is 43,560 square feet. 

A troy pound = 0*822857 avoirdupois lbs. = 5,760 grains. 

A troy ounce = 480 grains. 

An avoirdupois ounce = 437 '5 grains. 

An avoirdupois pound = 7,000 grains. 

A long ton is 2,240 Ibs. avoirdupois. 

A short ton, 2,000 Ibs., or 29,1661 troy oz. 

1,000 feet (board measure) of dry white pine = 4,000 Ibs. 

1,000 feet (board measure) of green white pine = 6,000 Ibs. 

One cord of seasoned wood = 128 cubic feet. 

One miner's inch = 2,159 cubic feet per twenty-four 
flours = 0*025 cubic feet per second. 

1 metre = 3*28 feet. 

1 gramme = 15*43 grains. 

An " assay ton" (2,000 Ibs. ton) = 29166 grammes, or 
450*1 grains. 

Vein with 2 inches solid galena has Ij tons in every 
6 by 6 feet of vein. 



TABLE OF WEIGHTS. 69 

TABLE OF WEIGHTS OF VARIOUS SUBSTANCES. 





Weight per 
Cubic Foot. 


Cubic Feet per 
Long Ton 
(2,240 Ibs.). 




Ibs. 




Gold (pure) 


1203 


1-87 


Lead 


710 


3-15 


Silver 


655 


3-42 


Rolled iron - - - - 


480 


4-68 


Galena .... 


468 


4-79 


Niccolite .... 


468 


4-79 


Cerussite - 


400 


5-60 


Chalcocite - - - - 


355-7 


6-30 


Magnetite - - - 


318-6 


7-03 


Specular iron ore 


327-4 


6-84 


Pyrites .... 


312 


7-18 


Barytes - - - 


277-5 


8-07 


Chalcopyrite 


262-1 


8-55 


Zinc blende - - - - 


250 


8-96 


Brown Hematite - 


250 


8-96 


Limestone - - - - 


168 


13-30 


Granite . . - - 


147 to 174 


15-2 to 12-8 


Porphyry - * 


366 to 171 


13-5 to 13-1 


Slate 


162 to 178 


13-8 to 12-6 


Quartz 


165-2 


13-6 


Sandstone - - - - 


130 to 157 


17-3 to 14-3 


Brick 


125 to 135 


18-1 to 16 


Clay - - - - - 


119-7 


18-7 


Anthracite - 


85-4 to 99 


26 -2 to 22 -6 


Bituminous coal - 


75 to 83 


29 -8 to 26-1 


Cannel coal . . . 


75 


29-8 


Lignite .... 


78 to 84 


28-7 to 27 


Oak 


48 to 58 


40 to 46 -6 


Ash 


43 to 47 


45 to 50 


White pine - 


34 


65 


Yellow pine 


32 


70 


Wood charcoal (heaped measure) 


12 -5 to 39 


57-5 to 180 




pine walnut 





70 FIELD TESTING FOR GOLD AND SILVER. 



PLACER AND HYDRAULIC MINING. 
Weights of Placer Ground. 

1 cubic foot of dry loose loam weighs 72 to 80 Ibs. 

packed 90 to 100 

wet loose 66 to 68 

packed 85 to 95 

fine sand dry 100 to 117 

wet 82 to 90 
1 cubic foot of ordinary gravel, free 
from cement, and containing no 

heavy boulders (dry) weighs 90 to 100 

The same (wet) 80 to 90 
1 cubic foot filled with boulders not over 

6 inches in diameter (dry) weighs 95 to 105 

The same (wet) 85 to 95 

1 cubic inch of water weighs *036 

foot 62-5 

yard 1687'5 

Moving Power of Water. 

16 feet per minute begins to wear away fine clay. 

30 just lifts fine sand. 

39 lifts sand as coarse as linseed. 

45 moves fine gravel. 

120 inch pebbles. 

200 pebbles as large as eggs. 

320 boulders 3 to 4 inches thick. 

400 6 to 8 

600 12 to 18 




REPAIRING A SLUICE-BOX. 



{To face p. 70. 



PLACER AND HYDRAULIC MINING. ft 

Cubic Yards of Dirt which may be washed per Day 
(Ten Hours) per Man. 





Ordinary. 


Cemented. 


By the pan 


1 c. yd. 


j c. yd. 


rocker 


2 


2 


long torn 


5 to 6 


3 to 5 


,, sluice 


10 to 20 


6 to 12 


hydraulic ) 
monitor > 


100 to 1,000 


100 to 1,000 


boom 


unlimited 


unlimited 



Cleaning Gold Nuggets. Boil in water, and after- 
wards wash with alum water ; then boil with hydrochloric 
acid and salt and water. While gold is hot, wash with hot 
water, then put in strong ammonia and let it stand in it 
for a few hours. 

I 
Hydraulic Mining Notes. 

1. To find the area of a section of a flume with straight 
sides. Multiply the width of the bottom (in inches) by 
the height of sides (in inches) ; the product will be the 
area in square inches which, divided by 144, gives the 
area in square feet. 

2. To find the area of the section of a ditch with 
sloping sides. Add together the width at top and bottom 
(in inches), multiply this sum by the depth (in inches), 
and divide the result by 2. The quotient, divided by 144, 
will be the area in square feet. 

3. Measuring the water of streams or ditches. Mea- 
sure depth at regular intervals from side to side. Add all 
these depths together and divide the sum by the number 
of soundings. An average depth is thus gained. Cal- 
culate then the area of the section according to (1) above. 



7 1 FIELD TESTING FOR GOLD AND SILVER. 

Measure the velocity by means of a float, and make the 
test about the middle of the stream. Multiply the area 
by the velocity, and the product will be the flow. 

4. Making the preliminary survey of a hydraulic 
placer claim. First, lay off the dump ; second, decide 
how much grade and fall to give the sluices ; and third, 
find the least fall necessary between source of water and 
water-box. The remaining distance will then be the 
greatest head attainable. 



PART II. 
PRACTICAL MINERALOGY. 



WHAT IS A MINERAL? 

IT is not necessary for a prospector to know much 
chemistry, but it is impossible for him to form a clear 
and intelligent idea of a mineral or of a rock (composed 
of minerals) unless he appreciates the chemical character 
of a mineral. 

Minerals are composed of chemical elements, which are 
substances which cannot be further separated. A list 
of thirty of the more common of the seventy known 
elements is given in Appendix B (p. 136), with their 
chemical symbols and combining, or atomic, weights. 
When these elements unite together and form a compound, 
they always do so in fixed proportion and in definite 
weight. Therefore, in any pure mineral, whose compo- 
sition is known, the amounts of the elements going to 
make up any given mass of it can be calculated by a rule 
of three sum. 

For example, in galena (PbS) we have lead (Pb) = 207 
and sulphur (S) = 32, total 239. Therefore in 239 Ibs. of 
pure galena we will find 207 Ibs. of lead (86j per cent.), 
and so on in proportion. 

Thus any mineral that is pure enough to be weighed 
directly, or which can be concentrated pure and then 
weighed, can be estimated in this way, and the percen- 
tage content of the ore calculated in the field. 

The combination of two or more of these elements 
together gives rise to three classes of substances, namely, 
acids, bases, and sails. 



76 FIELD TESTING FOR GOLD AND SILVER. 

Oxides of non-metallic elements are acid. 

Oxides of metallic elements are bases. 

Where an acid and a base unite, one exactly neutralising 
the other, a substance is produced, having neither acid 
nor basic tendency. It is known as a salt. 

Most minerals are salts. 

There is only one common acid mineral, namely, quartz 
(SiO 2 ), or the oxide of the non-metallic element silicon. 

There are many minerals which are basic, such as 
hematite (Fe 2 O 3 ) and magnetite (Fe 3 O 4 ), the oxides of 
iron, and cuprite (CuO), the oxide of copper. 

Among the many minerals which are salts are common 
salt or sodium chloride (NaCl) ; limestone or calcite 
(CaCO 3 ), formed from the union of the oxide of calcium, 
(metal) and carbonic acid gas ; gypsum (CaSO 4 '2H 2 O), 
formed by the union of the oxide of calcium (metal) and sul- 
phuric acid; apatite,* "phosphate of lime" {CsL 3 (P^O 4 ) 2 } 9 
formed by the same base as above uniting with phos 
phoric acid. 

There are a great many minerals the acid member of 
which is silica, with one or more metallic oxides forming 
the basic member. These are known as silicates^ and 
felspar, mica, hornblende, pyroxene, talc, serpentine, etc., 
are examples. 

These facts are important to remember, because whole 
families of minerals and rocks are classified acid or basic 
according to the greater or lesser quantity of silica present 
in them. 



* Apatite contains also fluoride, or chloride, of calcium, often 
both. 



MINERALS. 77 

MINERALS. 

A mineral is an inorganic body composed of one or 
more elements. It has theoretically a definite chemical 
composition, and usually a regular geometric form. 

When a mineral has had an opportunity to form slowly, 
it generally has a certain individual external form known 
as its crystalline form. Such minerals commonly exhibit 
constant qualities as to composition, form, hardness, weight 
(specific gravity), and physical appearance. 

We therefore note that the principal characteristics 
of minerals are : 

1. Composition. This may sometimes vary by an ele- 
ment replacing a similar one to a greater or less extent. 
The more basic or metallic the mineral is, the heavier it 
will be. 

2. Crystalline Form. Minerals crystallise under six 
systems. Prospectors are familiar with the ordinary 
crystalline form of some of the common minerals, such 
as the cubes of iron pyrites, galena, and fluor spar ; the 
hexagonal prisms of quartz and mica ; the rhombic shape 
of calcite, dolomite or spathic iron ore. 

Systems. Examples. 

1. Isometric - - Pyrites and galena (lead ore). 

2. Tetragonal - - Cassiterite (tin ore). 

3. Orthorhombic - Stibnite (antimony ore). 

4. Monoclinic - - Pyroxene and hornblende. 

5. Triclinic - - Labradorite and albite. 

6. Hexagonal- - Hematite (iron ore) and quartz 

The crystallisation affects the internal structure of 
minerals so that some break along certain planes, known 



78 FIELD TESTING FOR GOLD AND SILVER. . 

as cleavage planes ; this serves as an additional means of 
identifying many minerals. As a familiar example in 
granite, we note the hackly surface of the quartz, which 
has no cleavage, and the smooth surfaces of both felspar 
and mica crystals which have cleavage planes. 

3. Hardness. This characteristic of a mineral is a very 
important guide in field work. The following minerals 
are taken as a standard scale of hardness : 

1. Talc. 4. Fluor-spar. 7. Quartz. 

2. Gypsum. 5. Apatite. 8. Topaz. 

3. Calcite. 6. Orthoclase felspar. 

Any minerals of hardness 1 and 2 are easily scratched 
with the nail ; 3 and 4 are readily scratched with a knife ; 
5 is scratched with difficulty, and 6 with much difficulty 
by a knife ; while 7 is distinctly harder than steel. 

A more exact scale of test can be made with a copper 
coin, a piece of glass, and a knife, viz. : 

1. .Easily scratched by the nail. 

2. Yields with difficulty to the nail. Does not scratch 

copper coin. 

3. Scratches and is scratched by copper coin. 

4. Not scratched by copper coin. Does not scratch 

glass. 

5. Scratches glass with difficulty, leaving its powder 

on it. Yields to the knife. 
t>. Scratches glass readily. Yields with difficulty to 

the knife. 
7. Does not yield to the knife. Yields to the edge of 

a file, though with difficulty. 



MINERALS. 79 

4. Specific Gravity. The specific gravity of a mineral 
is its weight as compared with the weight of an equal 
volume of water. For example, the specific gravity of 
gold is about 19, because it is that many times as heavy 
as the same amount of water. 

The specific gravity of a mineral or a rock is easily 
tested in the field by weighing about J Ib. of it, suspended 
by a thin string, on the scales used for weighing ore 
(see p. 13). Weigh it in the air, obtaining a weight (a). 
Then weigh it suspended in water (b). Subtract weight 
b from weight tf, getting a resulting weight (c\ Finally 
divide weight a by <:, and the result is the specific 
gravity of the specimen. 

For example, we will give the results of a trial of certain 
known specimens made in the manner above indicated, and 
by referring to the tables of " Common Ores" and " Rock- 
forming Minerals" it will be seen how closely the result 
tallies with the specific gravity of the rock or the mineral 
in question. 

EXAMPLE. 
A piece of quartz 

Weight in air 207 oz. (a) 

water 12'9 (6) ZL W = 2 - 6 5 sp. gr. 
~T8 (c) ' 8 W 

A piece of hematite (iron ore) 
Weight in air 8'85 oz. (a) 

water 6W (b) Eg W = 4 - 66 sp . gr . 
T90 (c) 

A piece of galena (lead ore) 
Weight in air 6*8 oz. (a) 



water 6 (b) . W = 7 - 6 sp . gr . 



8o FIELD TESTING FOR GOLD AND SILVER. 

A piece of granite (an acid rock) 
Weight in air 17*25 oz. (a) 

water 1070 (b) > W = 2 . 66 
6-55 (c) 

A piece of diallage (pyroxenite, an ultra-basic rock) 
Weight in air 20'25 oz. (a) 

water 14'10 (b) ^? = 3 '29 sp. gr. 

"e^ (c) 615W 

5. Lustre. May be of two main kinds metallic, like 
galena, etc. ; or vitreous (or glassy), like quartz, etc. 

6. Colour and Streak. If the mineral is more or less 
transparent, its colour may vary immensely, as for example, 
quartz is found from black to white. In opaque minerals 
the colour is fairly constant, as in galena, hematite, etc. 

The streak from the scratch of a knife, however, is quite 
important for field determination, for no matter how much 
the colour may vary, the streak, or powder, is the same 
colour. As for example, quartz, tin ore (cassiterite), and 
tourmaline give white streak or powder ; black or red 
hematite a red streak ; pyrargyrite and cinnabar a bright 
red streak, etc. 



COMMON ORES. 8 1 



TABLE OF COMMON ORES, AND THE 
MANNER OF USING IT. 

The characteristics of minerals have just been con- 
sidered, and they will now be given in a tabulated form 
opposite to the mineral (or ore) in question in the tables 
of " Common Ores " and " Rock-forming Minerals " which 
follow this. 

If the mineral is found which is thought to correspond 
to some common ore, the table can be consulted. In 
the table we will notice first the percentage of the metal 
which it carries, then its name, then its system of crystal- 
lisation, then its fracture, then its specific gravity, its 
hardness, its streak, its colour, the action of acids upon it 
(which will seldom be referred to in the field), and lastly 
the blow-pipe reaction. Under this last we see the 
names of certain elements, such as sulphur, iron, copper, 
silver, etc. 

In order to see if those mentioned elements are present,, 
we refer to the paragraphs under " Blow-pipe Reactions " 
immediately following the table, and by carrying out the 
tests described in the reactions, we can prove whether 
the mentioned elements are present or absent. 

We shall therefore finally have proved by test that the 
mineral we suspect corresponds in its characters to that 
mentioned in the table opposite to it. 

An "ore" is a mineral or mixture of minerals of an 
economic value, and the term is generally applied to 
metallic elements : therefore some of the minerals in 
the following list, properly speaking, should not com 
under the general heading of ores. 



FIELD TESTING FOR GOLD AND SILVER. 



TABLE D. COMMON ORES. 

Abbreviations S.C,, System of Crystallisation ; Sp. Gr., Specific 
Gravity ; H. , Hardness. 

Blow-pipe Reactions given in immediately succeeding paragraphs. 



Ores of 


Per 

cent. 


Name. 


SC 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Antimony 


71-8 


Stibnite 


3 


Sub-con- 


4-5 


2 


Metallic 










choidal 








Arsenic - 


46-1 


Mispickel 


6 


Uneven 


5-9 


3-5 


Sub-met- 






(arsenical 




granular 






allic 






pyrites) 












Bismuth - 




Native 


6 




9-7 


2 


Metallic 














to 
















2-5 






59-1 


Tetradymite 


6 


Uneven 


7-2 


1-5 


Metallic, 












to 


to 


splendent 












7-9 


2 






81-25 


Bismuthinite 


3 


Conchoi- 


6-4 


2 


Metallic 










dal 








Chromium 


46 


Chromite 


1 


Uneven 


4-3 


5-5 


Sub-met- 






(chrome iron 






to 




allic 












4-5 






Cobalt - 


28-1 


Smaltite 


1 


Granular, 


6-4 


5-5 


Metallic 










uneven 


to 


to 














7-2 


6 






29-5 


Erythrite 


4 




2-9 


1-5 


Pearly, 














to 


adaman- 














2-5 


tine, dull 


Copper - 




Native 


1 


Hackly 


8-9 


2-5 


Metallic 














to 
















3 






34*6 


Chalcopyrite 


2 


Conchoi- 


4-1 


3-5 


Metallic 






(yellow 




dal, 


to 


to 








copper 




uneven 


4-3 


4 








pyrites) 














55-58 


Bornite 


1 


Conchoi- 


4-4 


3 


Metallic 






(horse-flesh 




dal, 


to 










ore) 




uneven 


5-5 







COMMON ORES. 



TABLE D. COMMON ORES. 

Abbreviations S.C., System of Crystallisation ; Sp. Gr., Specific 
Gravity; H., Hardness. 

Blow-pipe Reactions given in immediately succeeding paragraphs. 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Lead gray 


Lead gray, 


Soluble in Hydro- 


Fusible, Sulphur, 




tarnishes 


chloric Acid 


Antimony 


Tin white 


Tin white 


Soluble in Nitric 


Partly volatilises 






Acid 


and fuses. 








Sulphur, Arsenic 








Iron. 


Silver white, 


Silver white, 


Soluble in Nitric 


Fusible, Volatile, 


reddish 


reddish 


Acid 


Bismuth. 


Steel gray 


Steel gray 


Soluble in Nitric 


Fusible, volatile, 






Acid 


Tellurium, 








Bismuth. 


Lead gray, 


Lead gray, 


Soluble in Nitric 


Fusible, Sulphur, 


tin white 


tin white 


Acid 


Bismuth. 


Brown 


Iron black, 


Not acted on 


Infusible, Iron, 




brownish 




Chromium. 




black 






Grayish black 


Tin white to 


Decomposed by 


Fusible, Arsenic, 




steel gray 


Nitric Acid 


Cobalt, Iron. 


Paler than 


Red, gray, 


Soluble in Hydro- 


Fusible, Arsenic, 


colour 


blue 


chloric Acid 


Cobalt, Water. 


Metallic, 


Copper red 


Soluble 


Fusible. 


shining 








Greenish black 


Brass yellow, 


Decomposed in 


Fusible, Sulphur, 




tarnishes 


Nitric Acid 


Iron, Copper. 


Pale grayish 
black 


Copper red to 
brown 


Partly soluble in 
Nitric Acid 


Fusible, Sulphur, 
Iron, Copper, 



FIELD TESTING FOR GOLD AND SILVER. 



Ores of 


Pei- 
cent. 


Name. 


SC. 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Copper - 


79-8 


Chalcocite 


3 


Conchoi- 


5-5 


2-5 


Metallic 


(contd.) 




(copper 




dal 


to 


to 








glance) 






5-8 


3 






Oto50 


Tetrahedrite 


1 


Sub-con- 


4-5 


3 


Metallic 










choidal, 


to 


to 












uneven 


5-1 


4-5 






83-8 


Cuprite 


1 


Conchoi- 


5-8 


3-5 


Adaman- 






(red copper) 




dal, 


to 


to 


tine, sub- 










uneven 


6-1 


4 


metallic, 
















earthy 




57-4 


Malachite 


4 


Sub-con- 


3-7 


3-5 


Adaman- 










choidal, 


to 


to 


tine, 










uneven 


4 


4 


vitreous 




55*2 


Azurite 


4 


Conchoi- 


3-5 


3-5 


Vitreous, 










dal 


to 


to 


adaman- 












3-8 


4-5 


tine 




36-0 


Chrysocolla 




Conchoi- 


2 to 


2 to 


Vitreous, 










dal 


2-2 


4 


earthy 


Gold - - 




Native 


1 


Hackly 


15-6 


2-5 


Metallic 












to 


to 














19-5 


3 






28-5 


Sylvanite 


5 


Uneven 


7-99 


1-5 


Metallic 












to 


to 














8-33 


2 






25-60 


Petzite 




Brittle 


8-8 


2-5 


Sub-met- 
















allic 


Iron 


60 


Limonite 




Fibrous, 


3-6 


5 


Silky, sub- 






(brown iron 




earthy 


to 


to 


metallic, 






ore) 






4 


5-5 


earthy 




70 


Hematite 


6 


Sub-con- 


4-5 


5-5 


Metallic 






(specular 




choid al, 


to 


to 








iron) 




uneven 


5-3 


6-5 






72-4 


Magnetite 


1 


Sub-con- 


4-9 


5-5 


Metallic, 






(black iron 




choidal 


to 


to 


sub-met- 






ore) 






5-2 


6-5 


allic 




46-7 


Pyrite 


1 


Conchoi- 


4-8 


6 


Metallic 






(iron py- 




dal, 


to 


to 








rites) 




uneven 


5-2 


6-5 





COMMON ORES. 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Blackish lead- 
gray 


Blackish lead- 
gray 


Soluble in Nitric 
Acid 


Fusible, Sulphur, 
Copper. 


Same as colour 
Brownish red 


Flint gray to 
iron black 

Red 


Decomposed by 
Nitric Acid 

Soluble in Hydro- 
chloric Acid 


Fusible, Sulphur, 
Antimony, Iron, 
Copper. 
Fusible, Copper. 


Paler than 
colour 


Green 


Soluble with 
effervescence 


Fusible, Copper, 
Water. 


Paler than 
colour 


Blue 


Soluble with 
effervescence 


Fusible, Copper, 
Water. 


White, when 
pure 
Yellow 


Green, blue, 
brown, black 
Yellow 


Decomposed 

Soluble in Aqua 
Regia 


Infusible, Copper. 
Water. 
Fusible. 


Steel gray to 
silver white 


White 




Tellurium, Gold, 
Silver. 


Iron black 

Yellowish 
brown 


Between steel 
gray and iron 
black 
Brown 


Soluble in Hydro- 
chloric Acid 


Tellurium, Gold, 
Silver. 

Infusible, Iron, 
Water. 


Red, reddish 
brown 


Steel gray, iron 
black, red 


Soluble in Hydro- 
chloric Acid 


Infusible, Iron. 


Black 

Greenish or 
brownish 
black 


Iron black 
Brass yellow 


Soluble in Hydro- 
chloric Acid 

Decomposed by 
Nitric Acid 


Fuses with diffi- 
culty, 
Iron. 
Fusible, Sulphur, 
Iron. 



FIELD TESTING FOR GOLD AND SILVER. 



Ores of 


Per 
cent. 


Name. 


s.c. 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Iron 




Marcasite 


3 


Uneven 


4-6 


6 


Metallic 


(contd.) 




(white iron 






to 


to 








pyrites) 






4-8 


6-5 






61-5 


Pyrrhotite 


6 


Sub-con- 


4-4 


3-5 


Metallic 






(magnetic 




choidal 


to 


to 








pyrites) 






4-6 


4-5 






48*22 


Siderite 


6 


Uneven 


3-7 


3-5 


Vitreous, 






(spathic 






to 


to 


pearly 






iron) 






3-9 


4-5 




Lead - 


86-6 


Galena 


1 


Sub-con- 


7-2 


2-5 


Metallic 










choidal, 


to 














even 


7-7 








42-4 


Bournonite 


1 


Conchoi- 


5-7 


3 


Metallic 










dal, 


to 














uneven 


5-5 








77-5 


Cerussite 


3 


Conchoi- 


6-4 


3 


Adaman- 






(white lead 




dal 




to 


tine, 






ore) 








3-5 


vitreous, 
















resinous 




68-3 


Anglesite 


3 


Conchoi- 


6-1 


275 


Adaman- 










dal 


to 


to 


tine 












6-3 


3 






76-2 


Pyromorphite 


6 


Sub-con- 


6-5 


3-5 


Resinous 






(phosphate 




choidal, 


to 


to 








of lead) 




uneven 


7-1 


4 




Manganese 


63-3 


Pyrolusite 


3 


Uneven 


4-8 


2 to 


Metallic 






(gray ore) 








2-5 








Wad 




Uneven 


3 


0-5 


Metallic, 






(bog man- 






to 


to 


earthy 






ganese) 






3-2 


6 






47-8 


Rhodochro- 


6 


Uneven 


3-4 


3-5 


Vitreous 






site 






to 


to 














3-7 


4-5 






about 


Franklinite 


1 


Conchoi- 


5 


5-5 


Metallic 




8 






dal 




to 
















6-5 




Mercury - 


86-2 


Cinnabar 


6 


Sub-con- 


8-9 


2 


Adaman- 










choidal, 




to 


tine, 










uneven 




2-5 


metallic 



COMMON ORES. 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Grayish or 


Bronze yellow 


Decomposed by 


Fusible, Sulphur, 


brownish 




Nitric Acid 


Iron. 


black 








Grayish black 


Bronze yellow, 


Soluble in Hydro- 


Fusible, Sulphur, 




copper red 


chloric Acid 


Iron. 


White 


Gray, brown, 


Slowly soluble 


Fuses with diffi- 




red, green, 


with efferves- 


culty. 




white 


cence 


Iron. 


Lead gray 


Lead gray 


Partly soluble in 


Fusible, Sulphur, 






Nitric Acid 


Lead. 


Pale grayish 


Copper red to 


Partly soluble in 


Fusible, Sulphur, 


black 


brown 


Nitric Acid 


Leadj Copper, 








Antimony. 


Uncoloured 


White, gray, 


Soluble in Nitric 


Fusible, Lead. 




blue, green, 


Acid 






black 






Uncoloured 


White, yellow, 


Soluble with diffi- 


Fusible, Lead, 




gray, green, 


culty in Nitric 


Sulphur. 




blue 


Acid 




White, 


Green, yellow, 


Soluble in Nitric 


Fusible, Phos- 


yellowish 


brown, white 


Acid 


phorus, Lead. 


Black, bluish 


Iron black, 


Soluble in Hydro- 


Infusible, Man- 


black 


steel gray 


chloric Acid 


ganese. 


Brown 


Black, bluish 


Soluble in Hydro- 


Infusible, Man- 




or brownish 


chloric Acid 


ganese, Water, 




black 




from most varieties 


White 


Rose red to 


Soluble with 


Infusible, Man- 




brown 


effervescence in 


ganese. 






warm Hcl. 




Reddish brown 


Iron black 


Soluble in Hydro- 


Infusible, Iron, 






chloric Acid 


Manganese, 








Zinc. 


Scarlet 


Red to lead 


Soluble in Aqua 


Volatile, Sulphur, 




gray 


Regia 


Mercury. 



FIELD TESTING FOR GOLD AND SILVER. 



Ores of 


Per 
cent. 


Name. 


b.C. 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Nickel - 


43-6 


Niccolite 


6 


Uneven 


7-3 


5 


Metallic 






(copper 






to 


to 








nickel) 






7-6 


5-5 






35-2 


Gersdorffite 


1 


Uneven 


5-6 


5-5 


Metallic 






(nickel 






to 


to 








glance) 






6-9 


6-2 




G4-9 


Millerite 


6 


Uneven 


4-6 


3 


Metallic 












to 


to 














5-G 


3-5 




Platinum 




Native 


1 


Hackly 


16 


4 


Metallic 












to 


to 














19 


4-5 




Silver - 




Native 


1 


Hackly 


10-1 


2-5 


Metallic 












to 


to 














11-1 


3 






87-1 


Argentite 


1 


Sub-con- 


7-1 


2 


Metallic 






(black sil- 




choidal, 


to 


to 








ver or silver 




uneven 


7-3 


2-5 








glance) 














59-9 


Pyrargyrite 


6 


Conchoi- 


5-7 


2 


Metallic, 






(ruby silver 




dal 


to 


to 


adaman- 






or dark red 






5-9 


2-5 


tine 






silver ore) 














65-4 


Proustite 


6 


Conchoi- 


5-4 


2 


Adaman- 






(light red 




dal, 


to 


to 


tine 






silver ore) 




uneven 


5-5 


2-5 






68-5 


Stephanite 


3 


Uneven 


6-2 


2 


Metallic 






(brittle 








to 








silver ore) 








2-5 






64 


Polybasite 


3 


Uneven 


6-2 


2 


Metallic 




to 










to 






72 










3 






75-2 


Cerargyrite 


1 


Conchoi- 


5*5 


1 


Resinous, 






(horn silver 




dal 




to 


adaman- 














1-5 


tine 




G2-8 


Hessite 


3 


Even 


8-3 


2 


Metallic 






(telluric 






to 


to 








silver) 






8-G 


3-5 





COMMON ORES. 



8 9 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Brownish black 


Pale copper 
red, tarnishes 


Soluble in Aqua 
Regia 


Fusible, Arsenic, 
Nickel. 


Grayish black 
Bright 


Silver white, 
steel gray 

Brass to bronze 
yellow 


Decomposed by 
Nitric Acid 

Soluble in Aqua 
Regia 


Fusible, Sulphur, 
Arsenic, Nickel 
(often Iron). 
Fusible, Sulphur, 
Nickel. 


Whitish steel 
gray 


Whitish steel 
gray 


Soluble in Aqua 
Regia 


Infusible. 


Silver white 


Silver white 


Soluble in Nitric 
Acid 


Fusible. 


Same as colour, 
but shining 


Blackish lead 
gray 


Partly soluble in 
Nitric Acid 


Fusible, Sulphur, 
Silver. 


Cochineal red 


Black to cochi- 
neal red 


Decomposed by 
Nitric Acid 


Fusible, Sulphur, 
Antimony, 
Silver. 


Cochineal red 


Cochineal red 


Decomposed by 
Nitric Acid 


Fusible, Sulphur, 
Arsenic, Silver. 


Iron black 


Iron black 


Decomposed by 
Nitric Acid 


Fusible, Sulphur, 
Antimony, 
Silver. 


Iron black 
Shining 


Iron black 

Gray, green, 
whitish 


Decomposed by 
Nitric Acid 

Insoluble 


Fusible, Sulphur, 
Antimony, 
Copper, Silver. 
Fusible, Silver. 


Lead gray, 
steel gray 


Lead gray, 
steel gray 


Soluble in Nitric 
Acid 


Fusible,Tellurium 
Silver. 



FIELD TESTING FOR GOLD AND SILVER. 



Ores of 


Per 

cent. 


Name. 


S.C. 


Fracture. 


S p r ; 


H. 


Lustre. 


Silver - 


53-1 


Stromeyerite 


3 


Sub-con- 


6-2 


2-5 


Metallic 


(contct.) 




(argenti- 




choidal 


to 


to 








ferous sul- 






6-3 


3-5 








phide of 
















copper) 












Tin 


78-6 


Cassiterite 


2 


Sub-con- 


6-4 


6 


Adaman- 






(tin stone) 




choidal, 


to 


to 


tine 










uneven 


7-1 


7 




Zinc 


80-26 


Zincite 


6 


Sub-con- 


5-4 


4 


Sub-ada- 






(red zinc 




choidal 


to 


to 


mantine 






ore) 






5-7 


4-5 






67 


Sphalerite 


1 


Conchoi- 


3-9 


3-5 


Resinous, 






(blend or 




dal 


to 


to 


adaman- 






black jack) 






4-2 


4 


tine 




52-0 


Smithsonite 


6 


Uneven 


4 


5 


Vitreous, 






(carbonate 






to 




pearly 






of zinc) 






4.4 








54-2 


Calamine 


3 


Uneven 


3-1 


4-5 


Vitreous, 






(silicate of 






to 


to 


adaman- 






zinc) 






3-9 


5 


tine, 
















pearly 


Aluminium 


13 


Cryolite 




Uneven 


2-9 


2-5 


Vitreous, 












to 3 




pearly 




22 


Beauxite 




Uneven 






Earthy 




var'ble 














Barium - 


65-7 


Barite 


3 


Uneven 


4-3 


2-5 


Vitreous, 












to 


to 


resinous, 












4-7 


3-5 


pearly 




77-7 


Witherite 


3 


Uneven 


4*2 


3 


Vitreous, 












to 


to 


resinous 












4-3 


4 




Carbon - 


85 to 


Anthracite 












(Fuels) 


95 
















75 to 


Bituminous 














85 


Coal 














60 to 


Brown Coal 














75 


















Graphite 


6 


Lamellar 


2 


Ito 


Metallic 














2 





COMMON ORES. 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Dark steel gray, 


Dark steel gray 


Soluble in Nitric 


Fusible, Sulphur, 


shining 




Acid 


Copper. 


White, grayish, 
brownish 


Brown, black, 
red, gray, 


Slightly acted on 


Infusible, Tin. 




white, yellow 






Orange yellow 


Red, orange 


Soluble 


Infusible, Zinc. 




yellow 






White to red- 


White, yellow, 


Soluble in Hydro 


Fuses with diffi- 


dish brown 


brown, black, 


chloric Acid 


culty. 




red, green 




Sulphur, Zinc. 


White 


White, gray, 


Soluble with 


Infusible, Zinc. 




green, brown 


effervescence 




White 


W T hite, bluish, 


Gelatinises 


Fuses with diffi- 




greenish, 




culty. 




yellowish, 




Zinc, Water. 




brown 






White 


White, red, 


Soluble in Sul- 


Fusible, Fluorine, 




brown, black 


phuric Acid 


Aluminium. 


Whitish 


Whitish to 


Soluble in Sul- 


Aluminium, Iron. 




brownish 


phuric Acid 




White 


White, blue, 


Insoluble 


Fuses with diffi- 




yellow, red, 




culty. 


White 


gray, brown 
White, 


Soluble in Hydro- 


Barium, Sulphur 
Fusible, Barium. 




yellowish, 


chloric Acid 






greenish 






Black, shining 


Black, steel 


Not acted on 


Infusible. Fine 




gray 




powder burns. 



FIELD TESTING FOR GOLD AND SILVER. 



Ores of 


Per 

cent. 


Name. 


S.C. 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Cadmium 


77-8 


Greenockite 


6 




4-8 


3 


Adaman- 














to 


tine 














3-5 




Calcium - 


80 in 


Gypsum 


4 


Uneven 


2-3 


1-5 


Pearly, 




CaSO 4 










to 


vitreous 














2 






89 to 


Apatite 


G 


Conchoi- 


2-9 


5 


Vitreous, 




92 of 






dal, 


to 




sub-resi- 




Ca 






uneven 


3-2 




nous 




Phos ate 


















Calcite 


6 


Conchoi- 


2-5 


2-5 


Vitreous, 










dal 


to 


to 


earthy 












2-7 


3-5 








Dolomite 


6 


Conchoi- 


2-8 


3-5 


Vitreous, 










dal, 


to 


to 


pearly 










uneven 


2-9 


4 




Molyb- 


59 


Molybdenite 


G 




4-4 


1 


Metallic 


denum 










to 


to 














4-8 


1-5 




Potassium 




Nitre 


3 


Conchoi- 


1-9 


2 


Vitreous 










dal 








Sulphur - 




Native 


2 


Conchoi- 


2 


1-5 


Resinous 










dal 




to 
















2-5 





Strontium 


56-4 


Celestite 


3 


Conchoi- 


3-9 


3 


Vitreous, 




(SrO) 






dal, 




to 


pearly 










uneven 




3-5 






70-3 


Strontianite 


3 


Uneven 


3-6 


3-5 


Vitreous, 




(SrO) 








to 


to 


resinous 












3-7 


4 




Sodium - 




Halite 


1 


Conchoi- 


2-1 


2.5 


Vitreous 






(common 




dal 


to 










salt) 






2-2 










Borax 


4 


Conchoi- 


1-7 


2 


Vitreous, 










dal 




to 


resinous 














2-5 





COMMON ORES. 



93 



Streak. 


Colour. 


Action of Acids. 


31ow-pipe Reactions. 


Orange yellow 


Yellow, 


Soluble in Hydro- 


Infusible, Sulphur 


to brick red 


orangeyellow, 


chloric Acid 


Cadmium. 




bronze yellow 






White 


White, gray, 


Soluble in Hydro- 


Fusible, Sulphur, 




yellow, red, 


chloric Acid 


Calcium, Water 




blue, black, 








brown 






White 


Green, blue, 


Slowly soluble in 


Fuses with diffi- 




white, gray, 


Nitric Acid 


culty, Calcium, 




yellow, red, 




Phosphorus. 




brown 






White, grayish 


White, gray, 


Soluble with 


Infusible, Cal- 




green, red, 


effervescence 


cium. 




yellow, black 






White, grayish 


White, gray, 


Slowly soluble 


Infusible, 




green, red, 


with efferves- 


Calcium, 




brown, yellow 


cence 


Magnesium. 




black 






Lead gray or 


Lead gray 


Decomposed by 


Infusible, Sulphur 


greenish 




Nitric Acid 


Molybdenum. 


White 


White 


Soluble in Water 


Fusible, 








Potassium. 


Same as colour 


Yellow, some- 


Insoluble 


Fuses, burns. 




times reddish 








or greenish 






White 


White, bluish, 


Insoluble 


Fusible, Stron- 




reddish 




tium, Sulphur. 


White 


Green, white, 


Soluble in Hydro- 


Fuses with diffi- 




gray, brown, 


chloric Acid 


culty. 




yellow 




Strontium. 


White 


White, often 


Soluble in Water 


Fusible, Sodium. 




tinted 






White 


White, grayish 


Soluble in Water 


Fuses to a trans- 




bluish, 




parent glass. 




greenish 




Boron, W r ater. 



FIELD TESTING FOR GOLD AND SILVER. 



TABLE E. COMMON ROCK-FORMING MINERALS. 
(See also description tttider Part III. ) 

Abbreviations S.C., System of Crystallisation ; Sp. Gr., Specific 
Gravity ; H. , Hardness. 

Blow-pipe Reactions given in immediately succeeding paragraphs. 



Class. 


Mineral. 


s.c. 


Fracture. 


Sp. 
Gr. 


H. 


Lustre. 


Quartz 


Crystalline 


6 


Conchoidal 


2-5 


7 


Vitreous, 




Calcedony 






to 




resinous 




Camel ian 






2-8 








Agate 














Onyx 














Jasper 
Flint 














Chert 












Felspar - 


Orthoclase 


4 


Conchoidal, 


2-4 


6 


Vitreous, 








uneven 


to 


to 


pearly 










2-6 


6-5 




/ 


Albite 


5 


Uneven 


2-5 


6 


Pearly, 












to 


to 


vitreous 












2-6 


7 








Oligoclase 


5 


Conchoidal, 


2-5 


6 


Vitreous, 










uneven 


to 


to 


pearly 


(Plagio- 
clase) 




Labradorite 


5 


Conchoidal, 
uneven 


2-7 
2-6 
to 


7 
6 


Pearly, 
vitreous 












2-7 










Anorthite 


5 


Conchoidal, 


2-7 


6 


Pearly, 










uneven 






vitreous 




\ 
















Kaolin 


3 




2-4 


1 


Pearly, 










to 


to 


earthy 










2-6 


2-5 




Mica 


Muscovite 


3 


Lamellar 


2-7 


3 


Pearly 










to 


to 












3 


2-5 





COMMON ROCK-FORM IKG MINERALS. 



95 



TABLE E. COMMON ROCK-FORMING MINERALS. 

(See also description tinder Part III.) 

Abbreviations S.C., System of Crystallisation ; Sp. Gr., Specific 

Gravity; H., Hardness. 
Blow-pipe Reactions given in immediately succeeding paragraphs. 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


White, often 


Colourless, 


Not acted on 


Infusible, Silicon. 


same as 


white, red, 






colour 


yellow,brown. 








blue, green, 








black 






Uncoloured 


White, red, 


Insoluble 


Fuses with diffi- 




gray, green 




culty. 


Uncoloured 


White, blue, 


Insoluble 


Difficultly fusible. 




gray, green, 








red 






Uncoloured 


White, green, 


Insoluble 


Fusible. 




red 






Uncoloured 


Gray, brown, 


Decomposed with 


Fusible. 




greenish, 


difficulty with 






white 


Hydrochloric 








Acid 




Oncoloured 


Colourless or 


Soluble without 


Fusible. 




white 


gelatinising in 








Com. Hydro- 








chloric Acid 




White, or 


White, yellowish 


Decomposed 


Infusible, Alumi- 


lighter than 


greenish, 




nium, Water. 


colour 


bluish, reddish 






Uncoloured 


White, gray, 


Insoluble 


Difficultly fusible, 




violet, black, 




Iron. 




red, brown, 








green, yellow 







9 6 



FIELD TESTING FOR GOLD AND SILVER. 



Class. 


Mineral. 


s.c. 


Fracture. 


S P . 
Gr. 


H. 


Lustre. 


Mica 


Phlogopite 


3 


Lamellar 


2-7 


2-5 


Pearly, 


(contd.) 








to 


to 


sub-metallic 










2-8 


3 






Biotite 


6 


Lamellar 


2-7 


2-5 


Vitreous, 










to 


to 


splendent, 










3 


3 


sub-metallic 


*Amphi- 


Hornblende 


4 


Sub-conchoi- 


2-9 


5 


Vitreous, 


bole 






dal, 


to 


to 


pearly, 








uneven 


3-4 


6 


silky 


* Pyroxene 


Augite 


4 


Uneven, 


3-2 


5 


Vitreous, 








conchoidal 


to 


to 


resinous, 










3-5 


6 


pearly 


Talc 


Talc 


3 


Scaly, 


2-5 


1 


Pearly 








earthy 


to 


to 












2-8 


1-5 




Chlorite - 


Chlorite 


6 


Lamellar 


2-3 


1 


Pearly 










to 


to 












2-8 


2-5 




Olivine - 


Olivine 


4 


Conchoidal 


3-3 


6-5 


Vitreous 










to 


to 












3-5 


7 




Serpentine 


Serpentine 




Conchoidal, 


25 


2-5 


Resinous, 








splintery 


to 


to 


pearly, 










2-6 


4 


earthy 



* Amphibole and pyroxene are very much alike, and when there is no crystalline 
structure it is impossible to distinguish between them. Amphibole crystals are usually 
long and bladed, though sometimes stout. Pyroxene crystals are usually thick and 
stout, never having a slender bladed form. 



COMMON ROCK-FORMING MINERALS. 



97 



Streak. 


Colour. 


Action of Acids. 


Blow-pipe Reactions. 


Uncoloured 


Yellowish, 


Decomposed by 


Fusible, Iron. 




brown, green, 


Hydrochloric 






white 


Acid 




Uncoloured 


Green, black, 


Decomposed by 


Fusible, Iron. 




brown, red, 


Hydrochloric 






white 


Acid 




White, or paler 


White through 


Slightly soluble 


Fusible. 


than colour 


green to 








black 






White, gray, 


White through 


Slightly soluble 


Fusible. 


grayish green 


green to 








black 






White, or 


Blue, green, 


Insoluble 


Fuses with diffi- 


lighter than 


red, gray, 




culty, 


colour 


brown, white 




Magnesium. 


Greenish 


Green, yellow 


Decomposed by 


Fuses with diffi- 


white 




Sulphuric Acid 


culty. 








Iron. 


Greenish 


Olive green, 


Soluble and 


Infusible, Silica, 


white 


also yellow 


gelatinising 


Magnesium, Iron 




and brown 






White, gray 


Green, red, 


Decomposed by 


Fuses with diffi- 




yellow 


Hydrochloric 


culty. 






Acid 


Water. 



Graphite, Halite, Limonite, Hematite, Magnetite, Calcite, Gypsum, 
Dolomite, Siderite, which may be considered as rock-forming minerals^ 
are given in the table above, under ores. 



98 FIELD TESTING FOR GOLD AND SILVER. 



BLOW-PIPE REACTIONS. 

Detailed instructions in blow-pipe work of a simple 
nature, connected with the determination of gold and 
silver values in ores, will be found above, but as a matter 
of convenience and reference for those who have some 
knowledge of blow-pipe work the following more advanced 
information is given. 

The examination of assay with borax and salt of phos- 
phorus is generally made on platinum wire where the 
colour of the bead is more readily observed. Make a 
small loop in the end of the platinum wire, heat it to 
whiteness in the blow-pipe flame, and dip it into powdered 
borax or salt of phosphorus ; heat again in the blow-pipe 
flame (adding more of the reagent if necessary) until a 
clear glassy bead is formed. While the bead is hot and 
soft, touch it to a minute speck of the assay, and heat 
again in the oxidising, then in the reducing flame. If no 
distinct colour is produced, add a little more of the assay 
to the same bead, and heat again, repeating the operation 
as many times as may be necessary. 

The examination with soda is generally performed on 
charcoal in the reducing flame. When the result looked 
for is the production of minute globules of metal, care 
should be taken that they do not escape observation. If 
necessary a portion of the charcoal around the assay may 
be cut out, ground up with a little water in a small mortar, 
and the charcoal and soda washed away. Any shining 
particles of metal may then be readily detected. When 
two or more metals are present an alloy is usually formed. 

Aluminium. Heat in the oxidising flame a small frag- 
ment of the mineral on charcoal or in platinum-pointed 




WHAT is IT? 



[ To face p. 98. 



LOW-PIPE REACTIONS. 99 

pincers, moisten with a drop of the cobalt solution, and 
heat again If the mineral assumes a blue colour, it 
indicates the presence of aluminium. 

This test is not applicable to fusible minerals, as fusible 
silicates give the same result, nor to minerals not white 
or nearly so after ignition. If the assay is not sufficiently 
porous to absorb the solution, it should be powdered. 

Antimony. On charcoal the assay yields dense white 
inodorous fumes which partly escape and partly condense 
on the coal. In the open tube, similar results are obtained. 
In a closed tube, when sulphur is present, the mineral 
yields a sublimate, black while hot, but becoming brownish 
red when cold. 

Arsenic. On charcoal most compounds of arsenic yield 
a white coating and evolve a garlic odour. Arsenic and 
some of its compounds when heated in a closed tube give 
a sublimate which has a metallic lustre ; if the mineral 
contains sulphur as well as arsenic, a red or yellow sub- 
limate of a sulphide of arsenic may be formed. In an 
open tube a white sublimate of arsenious oxide is produced, 
and the characteristic garlic odour given off. Some 
compounds of arsenic impart a light blue colour to the 
outer blow-pipe flame. 

Barium. A yellowish green colour is imparted to the 
outer blow-pipe flame by many of the compounds of 
barium. 

Bismuth. Before the blow-pipe on charcoal bismuth 
yields a coating which is dark orange yellow while hot 
and lemon yellow when cold, the yellow coating being 
usually surrounded by a white ring. 



IOO FIELD TESTING FOR GOLD AND SILVER. 

Boron. Boron imparts a bright yellowish green colour 
to the blow-pipe flame ; this is heightened by moistening 
the assay with sulphuric acid before heating. If the 
result is not satisfactory, mix one part of the powdered 
mineral with one part fluorite and three of potassic 
bisulphate and fuse on platinum wire ; boron, if present, 
will impart the green colour to the flame at the instant of 
fusing. 

Cadmium. Before the blow-pipe on charcoal cadmium 
gives a coating which is, when cold, reddish brown. The 
lest is more delicate when soda is used. 

Calcium. Imparts a brick red colour to flame, and sub- 
stance glows with white look of alkali earths. 

Carbonates. Give an effervescence of CO 2 in salt of 
phosphorus bead in a loop of platinum wire. 

Chromium. With borax both in the oxidising and 
reducing flame chromium gives a bead which is green 
when cold. Tin causes no change. 

Cobalt. With borax on platinum wire, minerals con- 
taining cobalt give a blue bead. If arsenic or sulphur is 
present the assay should first be heated on charcoal till 
fumes are no longer emitted. If a small quantity of iron 
is present the bead will be green while hot but blue when 
cold. 

Copper. When copper characterises a mineral it can 
be reduced to the metallic state by heating the assay with 
soda on charcoal. With borax or salt of phosphorus a 
red bead is formed in the reducing flame; in the oxidising 
flame the bead is green while hot but becomes greenish 
blue or blue on cooling. When the bead is formed on 
charcoal with borax or salt of phosphorus in contact with 



BLOW'-PIPE REACTIONS. 1OI 

tin it assumes a x^ery clianteterfstic ifcd colour. Most 
copper compounds colour the flame green. 

Fluorine. Fluorine combined with weak bases and 
little water may be tested by heating the substance in a 
closed tube in which a strip of moistened Brazil-wood 
paper is inserted. The paper becomes straw yellow, and 
a ring of silica is deposited near the assay. Another 
process by which the presence of fluorine in any combina- 
tion may be shown, is to mix the pulverised assay with 
some salt of phosphorus previously fused on charcoal and 
powdered, and heat the mixture in an open glass tube in 
such a way that the flame may be carried inside the tube 
by the current of air. Fluorine is recognised by its pun- 
gent odour, its effect on glass, and by moistened Brazil- 
wood paper placed in the upper end of the tube becoming 
straw yellow. 

Gold. When gold is in combination with metals which 
are volatile at a high temperature, e.g., tellurium, mercury, 
antimony, it is only necessary to heat the alloy on char- 
coal with the oxidising flame, when the gold remains 
behind in a pure state, and may be recognised by its 
physical properties. Lead is removed by the process of 
cupellation, as explained under " Silver." 

When associated with copper, the presence of which is 
easily detected by salt of phosphorus on charcoal, the 
alloy, for example gold coin, is dissolved in pure melted 
lead, and the new compound subjected to the process of 
cupellation on bone-ash. Copper is by this means entirely 
removed. To test the remaining globule for silver, it is 
treated with salt of phosphorus on charcoal in the oxi- 
dising flame ; the silver is gradually oxidised and dissolved 
by the glass, which, when cold, assumes an opal-like 



102 FIELD TESTING FO*R GOLD AND SILVER. 

appearance: To determine approximately the relative 
proportions of the two metals, the metallic globule is 
taken from the cupel, placed in a small porcelain dish 
containing some nitric acid, and heat applied. If the 
alloy contains 25 per cent, of gold, or less, it turns black, 
the silver is gradually dissolved, and the gold remains 
behind as a brown or black spongy or pulverulent mass. 
If the alloy contains more than 25 per cent, of gold, the 
globule turns also black, but the silver is not dissolved. 
If both metals are present in about equal proportions, 
the globule remains unaltered. If the amount of gold is 
considerable, it is indicated by the colour of the alloy. 

In both of the latter cases it must be fused on coal 
with borax and at least twice its weight of silver, free 
from gold, and then treated with nitric acid, when the 
separation will be complete. To form a gold button, it 
must be well washed with distilled water and fused on 
coal with borax, and it will then have the pure gold 
colour and bright surface. 

When associated with metals which, per se, are infusible 
before the blow-pipe, as, e.g., platinum, iridium, palladium, 
the metallic globule obtained by cupellation shows much 
less fusibility than pure gold. The exact nature of the 
foreign metals cannot be ascertained before the blow-pipe ; 
the humid way must be resorted to. 

Iodine. Fused on charcoal, iodides give fumes of 
iodine. Fused with potassic bisulphate in a test tube, 
compounds of iodine yield violet vapours, which condense 
in upper part of the tube. 

Iron. With borax on platinum wire, a very little iron 
with the oxidising flame gives a glass which is yellow 
when hot, colourless on cooling ; with more, the glass is 



BLOW-PIPt: REACTIONS. 103 

red while hot, yellow when cold; with still more, it is 
dark red when hot, and yellow when cold. In the re- 
ducing flame, the glass becomes bottle green. Minerals 
containing much iron become magnetic when highly 
heated in the reducing flame, especially if soda is used. 

Lead. Fused with soda in the reducing flame on 
charcoal, compounds of lead yield a globule of the metal. 
When heated on charcoal a coating is produced which is 
lemon yellow while hot, and sulphur yellow when cold. 
The coating imparts to the reducing flame an azure blue 
colour. 

Lithium. Some compounds of lithium colour the blow- 
pipe flame bright purple-red when heated in the platinum 
forceps. To obtain the best result, mix one part of the 
powdered minerals with one part each of fluorine and 
potassic bisulphate, make the whole into a paste with a 
little water, and fuse on platinum wire, when even if but 
little lithium is present, the characteristic colour will be 
imparted to the flame. 

Magnesium. Proceed as when testing for aluminium. 
A magnesium mineral will assume a pale red or pink 
colour. The test is applicable to both fusible and infusible 
minerals which are white or nearly so after the first 
ignition. 

Manganese. Manganese is very readily detected by 
fusing a little of the powdered substance with two or three 
times its volume of soda on platinum-foil. A green mass 
flows around the undissolved portion, and on cooling 
becomes bluish green. With borax on platinum wire 
manganese yields in the oxidising flame a glass which 
is violet when hot, but on cooling becomes violet red. 
An excess renders the glass quite black and opaque. 



104 FIELD TESTING FOR GOLD AND SILVER. 

Mercury. Compounds of mercury, when heated in a 
closed tube with soda, yield a sublimate of metallic 
mercury, which may be rubbed into globules with a piece 
of copper wire. 

Molybdenum. Molybdenum colours the blow-pipeflame 
yellowish green. Its compounds before the blow-pipe on 
charcoal yield a coating which is yellowish while hot and 
white when cold. The white coating assumes an azure 
blue colour when touched with an intermittent reducing 
flame. 

Nickel. When volatile substances are present, the 
assay must be strongly heated on charcoal in the reducing 
flame until it no longer emits fumes or odours. With 
borax on platinum wire, nickel yields a bead in the 
oxidising flame which is violet while hot, but reddish 
brown when cold. In the reducing flame the bead 
becomes gray and cloudy, and sometimes opaque, from 
a separation of metallic nickel. With continued blowing 
the metal collects together, and the bead becomes colour- 
less. The reaction is obscured by the presence of iron, 
cobalt, or copper. 

Phosphorus. Phosphates impart a dirty green or bluish 
green colour to the blow-pipe flame. The colour is more 
distinct if the powdered mineral is first moistened with 
sulphuric acid and then fused on platinum wire. 

Platinum. White metal, infusible. If in form of " sper- 
rylite " fuses to white brittle button, fumes of As 2 O 3 . 

Potassium. Potassium imparts a pale violet colour to 
the blow-pipe flame. The colour is obscured if sodium 
or lithium is present. 

Silicon. Silicates, when fused with soda on charcoal, 
dissolve with effervescence, forming a glass which is 



BLOW-PIPE REACTIONS. 105 

transparent wnile hot. With salt of phosphorus on 
platinum wire silicates are decomposed, the "skeleton 
of silica" floating in the clear hot bead. 

Silver. Many compounds of silver yield a globule of 
the metal when fused with soda on charcoal in the 
reducing flame. When treated for a long time with the 
reducing flame, a slight, dark-red coating is produced. 

When in combination with metals which are volatile 
at a high temperature, e.g., bismuth, lead, zinc, antimony, 
the substance is heated alone on charcoal, when, after 
volatilisation of these metals by long blowing, a button 
of pure silver remains behind, and a reddish coating is 
deposited on the charcoal. If associated with much lead 
or bismuth, these metals are best removed by cupellation, 
a process which is executed in the following manner. 

Break off the bowl of a common clay-pipe and make 
a suitable upright holder of twisted wire. Fill the pipe 
three-quarters full of any form of dry earth or pulverised 
rock, fill the remainder of the pipe with finely pulverised 
bone-ash with which previously may be advantageously 
mixed a minute quantity of soda, and then dampened to 
an almost imperceptible degree. The top is made smooth 
and slightly concave by pressing on it with the head of an 
ordinary carriage bolt. The cupel is then dried by the 
blow-pipe with the flame of a candle, gas, or spirit lamp. 
On this little cupel the assay is placed, and heated with 
the oxidising flame until the whole of the lead or bismuth 
is oxidised and absorbed by the cupel. When the assay 
is once fused the blue point of the flame can be held 
well away from it, the operation will proceed rapidly, 
and there will be less loss in silver than if greater 
heat be used. The silver, or if gold is present, the 



106 FIELD TESTING FOR GOLD AND SILVER, 

alloy of silver and gold, remains as a bright metallic 
button on the cupel. 

When combined with metals which are not volatile, but 
which are more easily oxidised than silver, the presence 
of this metal may in some cases be detected by simply 
treating the alloy with borax or salt of phosphorus on char- 
coal. Copper, nickel, cobalt, etc., are oxidised and their 
oxides dissolved by the flux, while silver remains behind 
with a bright metallic surface. But when these metals 
are present to a considerable extent, another course has 
to be pursued, a course which may always be taken when 
a substance is to be assayed for silver, or silver and gold. 

The assay-piece is reduced to a fine powder, mixed 
with vitrified borax and metallic lead (the quantities of 
which altogether depend upon the nature of the substance, 
and for which, therefore, no general rule can be given), 
and the mass placed in a cylindrical hole of the charcoal. 
A powerful reducing flame is given until the metals have 
united to a button, and the slag appears free from metallic 
globules. The flame is now converted into an oxidising 
flame and directed principally upon the button. Sulphur, 
arsenic, antimony, and other very volatile substances are 
volatilised; iron, tin, cobalt, and a little copper and nickel 
become oxidised and absorbed by the flux ; silver and 
gold, and the greater part of the copper and nickel, remain 
with the lead (and bismuth if present). When all volatile 
substances are driven off, the lead begins to become 
oxidised and the button assumes a rotary motion ; at this 
period the blast is discontinued, the assay is allowed to 
cool, and, when perfectly cold, the lead button is separated 
from the glass by some light strokes with a hammer. 
It is now placed on a cupel of bone-ash and treated with 
the oxidising flame until it again assumes a rotary motion. 



feLOW-PIPE REACTIONS. 167 

If much copper or nickel is present the globule becomes 
covered with a thick infusible crust which prevents the 
aimed-at oxidation ; in this case another small piece of 
pure lead has to be added. The blast is kept up until the 
whole of the lead and other foreign metals, viz., copper 
and nickel, are oxidised ; this is indicated by the cessation 
of the rotary movement, if only little silver is present, or 
by the appearance of all the tints of the rainbow over the 
whole surface of the button, if the ore was very rich in 
silver ; after a few moments it takes the look of pure 
silver. The oxides of lead, copper, etc., are absorbed by 
the bone-ash, and pure silver, or an alloy of silver with 
other noble metals remains behind, and the button may be 
tested for gold, etc., after the method given under "Gold." 

Sodium. Compounds of sodium impart an intense 
yellow colour to the blow-pipe flame. 

Strontium. When a mineral contains strontium, it 
colours the blow-pipe flame bright red. When moistened 
with hydrochloric acid the colour imparted to the flame 
is more intense. 

Sulphur. Sulphides yield fumes of sulphur when heated 
in charcoal, in a closed tube or in an open tube. A 
compound of sulphur when heated on charcoal with soda 
yields a mass which stains a silver coin black or brownish 
black when moistened and placed upon it. 

Tellurium. On charcoal tellurium gives a white coating 
and colours the reducing flame green. In an open tube 
a white or whitish sublimate is produced which, before 
the blow-pipe, fuses to clear colourless drops. 

Tin. Fused with soda on charcoal in the reducing 



Io8 FIELD TESTING FOR GOLD AND SILVER. 

flame, compounds of tin yield a globule of the metal, and 
at the same time a coating is formed on the coal which is 
slightly yellow when hot but is white when cold. The 
reduction of the tin is much assisted when a little cyanide 
of potassium is used with the soda. This coating, 
moistened with the cobalt solution and heated in the 
oxidising flame, assumes a bluish green colour. 

Titanium. On platinum wire with salt of phosphorus 
in the oxidising flame, titanium forms a clear bead which 
appears yellow while hot if much is present, but becomes 
colourless on cooling. The same bead reddens and 
finally assumes a violet colour in the reducing flame if 
treated with tin. If iron is present the reaction will be 
obscured. 

Tungsten. With salt of phosphorus on platinum wire 
in the oxidising flame a yellowish or colourless bead is 
produced which, treated with the reducing flame, is green 
while hot but blue when cold. On charcoal with salt of 
phosphorus in the reducing flame the bead becomes a 
deep green if treated with tin ; the reaction is obscured if 
iron is present. 

Water. When the powdered mineral is heated in a 
closed tube, water, if present, will be condensed on the 
colder portion of the tube and may be tested with litmus 
paper to ascertain if it is acid or alkaline. 

Zinc. Some compounds of zinc when heated on char- 
coal, either alone or with soda, yield a coating which is 
yellow while hot but white when cold. The coating wet 
with the cobalt solution and then heated assumes a fine 
yellowish green colour which is most distinct when cold. 



GEOLOGY. 109 

GEOLOGY. 

We have now considered the chemical aspects of 
minerals, and the characteristics of minerals both when 
of economic value or when forming the component 
parts of rocks and rock masses. Where the aggre- 
gations of minerals comprise rock masses, the considera- 
tion of them passes into the domain of Geology, and as 
it is extremely useful for prospectors to know the names 
of the common rocks that are likely to be met with in the 
field, some of those occurring most frequently will be 
described. 

As will have been noticed, the list of common rock- 
forming minerals is not large. So in like manner the 
broad families of rocks that are ordinarily found in the 
field are not many. But as every member of a family 
has its own individual characteristic, so the subdivision 
of rocks may be multiplied and divided into an almost 
infinite number of varieties. 

Mineral occurrences of economic value are generally 
found directly or indirectly associated with eruptive rocks, 
therefore more attention will be paid to them than to the 
families of aqueous rocks. 

Each mineral mentioned below will be found described 
in the table of " Rock-forming Minerals " (Table E) under 
the section on " Minerals." 

Aqueous Rocks. 

It is a pretty well established fact that the earth was 
originally in a molten condition, and therefore the primary 
rocks are of an igneous or melted variety. The decom- 
position and washing away of these has given rise to the 
different sorts of aqueous rocks. 



110 FIELD TESTING FOR GOLD AND SILVER. 

Let us follow the process down. We will take an 
igneous rock composed of free quartz and silicates, such 
as felspar and mica (containing aluminium, iron, etc.), 
granite for example. This rock in decomposing and 
wearing down will form sand and sandstones from the 
little grains of quartz, and clays* will result from the 
decomposed mica and felspar. Thus we have the origin 
of the sandstones on the one hand, and clay shales on the 
other hand. These quartz or siliceous rocks, and these 
clays or argillaceous rocks, form two of the three great 
families of aqueous rocks. Where rounded pebbles are 
included the rock is called a conglomerate, and if angular 
fragments occur it is known as a breccia. The third great 
group is made up of the limestones that are found so 
commonly in nature, whether formed from organic life 
by fossils, corals or shells, or by chemical depositions. 

Metamorphic or " Foliated" Rocks. 

Metamorphic rocks are those which have been subject 
to change through being buried beneath the surface and 
squeezed and twisted by pressure, which is constantly 
being exerted on the earth's surface, and by alteration by 
the action of thermal waters. The sand rocks are changed 
into quartzite, and the clay rocks are altered into slates, 
schists, and gneisses, and the limestones into marble and 
highly crystalline limestone (see pp. 131 to 134). 

Igneous rocks may be subject to the above-mentioned 
influences, as well as aqueous rocks, and become meta- 
morphosed. 

The family of metamorphic rocks are not so likely to be 
mineral-bearing, except when formed from igneous rocks, 

* When quite pure it is white, and is known as kaolin. 



GEOLOGY. Ill 

or in the case of an aqueous rock where such a substance 
as iron has been deposited in a bed and then changed by 
metamorphic influence, together with the accompanying 
aqueous rocks which contain it. 

Gneiss. The common metamorphic rocks, besides 
slates and marbles, are gneiss, which is generally of a 
laminated character, and commonly composed of quartz, 
felspar (orthoclase), and mica or hornblende. 

Mica Schist. Composed of mica and quartz (or kaolin 
or clay), or of mica alone. 

Where the mica is partly decomposed and has lost its 
lustre, with the addition of water, it is known as hydro- 
mica ; and where it forms the chief portion of schists, the 
rock is then known as hydro-mica schist. 

Talc Schist Composed chiefly of talc in a schistose 
condition, but the talc is often mixed with more or less 
quartz or felspar. 

Chlorite Schist. Composed chiefly of greenish chlorite 
mixed up with a certain amount of quartz, felspar, and 
micaceous matter, but the chlorite always present in 
sufficient quantity to give it a greenish colour. 

Hornblende Schist. This is composed of hornblende 
and quartz in alternating layers or folia. 

Serpentine. This rock, whether of eruptive or sedi- 
mentary origin, is fine grained, massive, compact, and 
varying in colour from very dark green to light greenish 
yellow. In most cases it is due to the decomposition of 
some ultra basic rock. 



112 FIELD TESTING FOR GOLD AND SILVER. 

Igneous Rocks. 

The igneous rocks are composed of two broad families 

Firstly, where the molten mass has cooled slowly at a 
great depth, and has subsequently been exposed by 
denudation. (Where it is thrust out from its source 
between layers of covering strata it is then known as 
a " laccolite.") The cooling has been very slow, under 
great pressure. 

This slow cooling under pressure has allowed the 
crystals to form out individually and clearly, and we 
notice the mottled character of the rock quite plainly, 
being able to discern such minerals as quartz, felspar, 
hornblende, etc. 

Secondly, where we see the close-grained character, 
the molten matter has been poured out on the earth sur- 
face under no great pressure, and has cooled rapidly. 
The texture of igneous rocks varies from coarsely crystal- 
line to glassy structure, and in the table given below they 
are classified according to their texture, as well as by the 
minerals of which they are composed. 

COARSELY CRYSTALLINE ROCKS. 

Granite. The component parts of granite are quartz 
and orthoclase felspar with mica or hornblende, and 
according to the occurrence of these last two minerals it 
is frequently called either a mica-granite or a hornblende- 
granite. 

Granite is a rock in which veins of precious metals are 
frequently formed, and in some instances it is charged 
with a good deal of mineral matter chiefly in the form 
of small crystals of iron pyrites disseminated through it. 
The granite which shows signs of alteration is more likely 



GEOLOGY. TI3 

to be mineral-bearing than that which is hard and glassy, 
and the gray granites are more promising than the reddish 
varieties. 

Syenite is composed of orthoclase felspar and generally 
hornblende, or some mica. A small amount of quartz 
will bring it into the condition of a quartz-syenite, from 
which it passes into a typical granite. 

Greenstones. Dark greenish coloured rocks, which are 
common igneous rocks, are known as greenstones^ and 
this name can properly be applied to the classes of rocks 
known as diorite, dolerite, diabase, basalt, etc. It is often 
impossible to tell to which grade a rock should belong 
without microscopic examination, therefore the old- 
fashioned name of greenstones can well be applied to the 
moderately crystalline igneous class of rocks where the 
hornblende or augite (or their green decomposition 
products) give them a dark and greenish hue. 

Diorite. This rock consists of basic felspar (plagioclase, 
most commonly oligoclase) and hornblende. Mica is 
sometimes present with the hornblende, and, as in syenite, 
quartz may also occur to a limited extent, so that there 
is such a rock as a quartz-diorite, though it is not 
common. 

Gabbro is a coarsely crystalline rock composed of 
plagioclase felspar and pyroxene, often olivine, and 
generally some magnetite. 

Where hypersthene appears with, or in place of, diallage, 
the rock is known as norite^ in which commonly there is 
black mica and more or less magnetite or titanite. 

Dolerite and Diabase are names given to finer grained 
H 



ii4 FIELD TESTING FOR GOLD AND SILVER. 

rocks of the gabbro class, olivine occurring in some 
varieties. 

The alteration of these rocks gives rise to the mineral 
chlorite which is the chief cause of the green colour so 
common in this class of dike rock. It must be remembered 
that the more basic the rock is, the more liable it is to 
decomposition. 

Peridotite and other ultra-basic rocks consist mainly 
of olivine (or its decomposition product "serpentine"), 
augite or hornblende or allied minerals. 

COMPACTLY CRYSTALLINE, SEMI-GLASSY, AND GLASSY 
ROCKS. 

The close-grained and glassy igneous rocks are not 
so common as the more coarsely crystalline varieties. 
Types of them occur which correspond to each of the 
above-mentioned coarsely crystalline rocks. An inter- 
mediate or compactly crystalline state of the granite type 
is known as quartz -felsite, of the syenite type as felsite, 
of the diorite type as diorite-porphyry, and the gabbro 
type as dolerite or diabase. 

The most common semi-glassy igneous rock is one 
which represents the semi-glassy type of the basic rocks. 
It is known as basalt, which often is found in columnar 
form. 

The semi-glassy type of granite is known as rhyolite, 
and of syenite as trachyte, and of diorite as andesite. 

The glassy state of the granite and syenite type is known 
as obsidian, and the corresponding condition of the basic 
rocks is very rare. 

The tables on pp. 116 and 117 will give as complete 
a comprehension of the rocks above mentioned as is 
necessary for the average prospector. 



GEOLOGY. 115 

DIAGNOSTIC CHARACTERS OF IGNEOUS 
ROCKS. 

1. Colour. The acid rocks (those containing much 
silica) are generally grey or light coloured. The inter- 
mediate rocks are generally dark gray or dark greenish 
gray. The basic rocks are generally black or greenish 
black. The ultra-basic rocks are generally black or 
green. 

2. Decomposition. The more acid rocks generally re- 
sist denudation better, and are comparatively fresh, while 
the basic rocks are often scaling and soft at the surface 
or covered with iron-rust. 

3. Specific Gravity. The more acid the rock is the 
lighter it is, and the more basic the higher will be its 
specific gravity. Therefore the determination of the 
specific gravity as described under "Minerals" (sub- 
heading "Specific Gravity") is of first-class importance 
(see pp. 78 and 79). It can be done in a moment or two 
with a cheap set of scales, and the specific gravity of 
most of the rocks generally met with is given in the fol- 
lowing table. 



Il6 FIELD TESTING FOR GOLD AND SILVER. 











3 






S 


Calcareous. 


: 


Limestones anc 
Gypsum. 


Limestones. 


Compact and Su 
crystalline Lim 
stones, Dolomil 


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lighly Crystallil 
and Serpentine 
Limestone. 










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THE PROSPECTOR'S MOUNTAIN HOME. 



[To face p. 119. 



PART III. 

I. GLOSSARY OF USEFUL MINING 
TERMS. 

II. COMMON ROCK-FORMING MINERALS 
AND ROCKS. 



GLOSSARY OF USEFUL MINING TERMS. 

Adit. A horizontal passage from daylight into a mine, 
which assists in the drainage. 

Alluvium. The gravelly and other deposits made by 
running streams, especially in times of flood. 

Amalgamation. The production of an amalgam or alloy 
of mercury ; also the process by which gold and silver 
are extracted from pulverised ores by producing an 
amalgam from which the mercury is afterwards expelled. 

Apex. The edge or outcrop of a vein. 
Argentiferous. Containing silver. 

Arrastra. A primitive contrivance for the reduction and 
amalgamation of free-milling gold or silver in ores. It 
consists of a shallow tub-shaped enclosure, usually about 
12 feet in diameter, formed of either iron, wood, or stone. 
An upright shaft fixed to pivots above and below stands 
in the centre, and from it arms extend to which horses or 
mules are attached. Blocks of stone attached by thongs 
or chains to these arms are dragged around upon the 
stone pavement or iron plate which forms the bottom in 
such a way that the front of the lower surface of each 
block is slightly raised so that it may pass over the finely 
broken ore and triturate it upon the bottom. After 
grinding the ore to a pulp, sufficient mercury is added 



122 FIELD TESTING FOR GOLD AND SILVER. 

to amalgamate all the precious metal supposed to be 
present, and the grinding process is continued for some 
time. 

Assay. To test ores and minerals, usually by smelting 
or blow-pipe examination. 

Auriferous. Containing gold. 

Bar-diggings. Gold-washing claims located on the 
bars (shallows) of a stream and worked when the water 
is low, or otherwise with the aid of coffer-dams or wing- 
dams. 

Battery. A set of stamps in a stamp mill comprising 
the number which fall in one mortar, usually five. 

Bed-rock. The solid rock underlying alluvial and 
other surface formations. 

Blossom. The oxidised or decomposed outcrop of a 
coal-bed. 

Blow-out. A large outcrop beneath which the vein is 
smaller. 

Bonanza. A body of rich ore. 

Bullion. Uncoined gold and silver. Base bullion is 
pig lead containing silver and some gold, which are 
separated by refining. 

Calcining. Burning or roasting ores or other minerals 
as part of their treatment for smelting, crushing, or other- 
wise utilising them. 

Cap, Cap-rock. An unscientific term used to indicate 
the country rock by which a vein is pinched at the 
surface. 



GLOSSARY OF MINING TERMS. 123 

Carbonates. The common term in the West for ores 
containing a considerable proportion of carbonate of 
lead. 

Casing. The lining of a shaft, the tubbing of a well ; 
also applied to the decomposed matter sometimes found 
between a vein and the wall-rock. 

Cement. Gravel firmly held in a silicious matrix, or 
the matrix itself. 

Chlorides. A common term for ores containing 
chloride of silver. 

Chloridise. To convert into chloride. Applied to the 
roasting of silver ores with salt, preparatory to amalgama- 
tion. 

Chlorination. The process of dissolving gold from re- 
fractory ores which have been pulverised and thoroughly 
oxidised by calcination. 

Chute. A channel or shaft underground, or an in- 
clined trough above ground, through which ore falls or is 
"shot" by gravity from a higher to a lower level. 

Cleaning Up. The process of collecting together the 
metal or ore which has accumulated in sluice-boxes or in 
the various contrivances for saving it by mining machinery. 

Clinometer. An apparatus for measuring vertical 
angles, particularly dips. 

Concentration. The removal by mechanical means of 
che less valuable or worthless portions of an ore. 

Country, Country Rock. The general rock-mass in 
which mineral veins or other deposits are held. 

Cradle. See Rocker, 



124 FIELD TESTING FOR GOLD AND SILVER. 

Cyanide Extraction. The process of leaching out gold 
by cyanide of potassium in a very dilute solution. A very 
valuable process for saving the fine gold escaping from 
stamp mills. 

Dead-roasting. Roasting carried to the farthest prac- 
ticable degree in the expulsion of sulphur. Same as 
roasting " sweet." 

Deposit, Irregular. Ore-bodies, not veins or beds. 

Dip. The angle, measured by the steepest line in the 
plane of a bed or vein from the horizon. 

Ditch. An artificial water-course, flume, or canal to 
convey water for mining. 

Drift. An underground passage ; a level or tunnel. 

Dump. The pile of rock which has been hoisted to the 
surface and deposited there. It may be said to be a 
low-grade ore reserve. 

Face. A perpendicular wall of rock ; the end of a drift, 
etc., in a mine. 

Fault. The term for any fissure accompanied by a 
displacement of the strata on either side. 

Feeder. A small vein joining a larger vein. 

Float. Broken and transported pieces of vein matter. 
If sharp and angular, they have not come far ; but if 
rounded and worn, they may have travelled some dis- 
tance. Also called shode or shode-stones. 

Floor. The stratum below a mineral bed. 




HYDRAULIC MINING. 



To face p. 124. 



GLOSSARY OF MINING TERMS. 125 

Flouring. The separation of quicksilver into globules 
which refuse to reunite. The coating of quicksilver with 
what appears to be a thin film of some sulphide is called 
"sickening." 

Flucan. Same as " Gouge." 

Flume. A wooden conduit bringing water to a mine 
or mill. 

Flux. In metallurgy, any substance added to facilitate 
the smelting of another. 

Foot-wall. The face of rock below a vein. 

Free. Native ; uncombined with other substances, as 
free gold or silver. 

Free-milling. Applied to ores which contain free gold 
or silver, and can be reduced by crushing and amalgama- 
tion, without roasting or other chemical treatment. 

Fuse. A tube, ribbon, or cord filled or saturated with 
a combustible compound, used for exploding powder. 

Gangue. The veinstone, veinstuff, or matrix of a vein 
in which the metallic contents are enclosed. The com- 
monest gangues are quartz, calcspar, fluorspar, barytes, etc. 

Gossan. A ferruginous crust filling the upper parts of 
pyritous veins or forming a superficial cover on masses 
of these ores. It consists principally of hydrate oxide of 
iron, and has resulted from the oxidation and removal of 
the sulphur as well as the copper, etc. 

Gouge. The layer of clay, or decomposed rock, which 
lies along the wall or walls of a vein. Also called 
"Flucan." It is not always valueless. 

Grass-roots. A miner's term equivalent to the surface. 

Hanging Wall The face of rock above a vein. 



126 FIELD TESTING FOR GOLD AND SILVER. 

Heave. A dislocation of the vein, apparently side- 
ways. 

Horn. An article made of an ox or buffalo horn, in 
which earth or pulp may be delicately tested by washing 
to detect gold, amalgam, etc. 

Horse. A mass of country rock lying within a vein. 

Hungry. A term applied to hard barren vein matter, 
such as white quartz. 

Hydraulic Mining. Washing down gold-bearing earth 
by means of a large and powerful jet of water. 

Lagging. The slabs or small timber placed between 
the main timber sets and the roof or walls to prevent 
small rock from falling into the drift. 

Level. A horizontal passage in a mine. 

Lixiviation. The separation of a soluble from an in- 
soluble material by means of steeping in a solvent. 

Lode. A mineralised fissure, generally applied to a 
large vein, or of local use in certain mining districts. 

Mill-run. A test of the value of a quantity of- ore in 
a battery, arrastra, etc. 

Mine. A place where mineral is worked below ground, 
and in which artificial light must be used. But in some 
countries, any mineral working. 

Mineral. Any constituent of the earth's crust that has 
a definite composition. 

Miner's Inch. The unit of measurement of water used 
by sluice and hydraulic miners. It is that amount of 
water hourly discharged through an opening 1 inch 
square under a head of 7 inches. If the head is 7 




SMALL TESTING STAMP-MILL. 



{To face p. 126. 



GLOSSARY OF MINING TERMS. 127 

nches and the hole is through a plank 2 inches thick, 
a miner's inch is equal to about 90 cubic feet per hour. 

Nugget. A lump of native metal, especially of a 
precious metal. 

Ore. A mineral of sufficient value (as to quality and 
quantity) to be mined with profit. 

Ore-shoot. A large and usually rich aggregation of 
mineral in a vein. Distinguished from pay-streak in that 
it is a more or less vertical zone or chimney of rich vein 
matter extending from wall to wall, and having a definite 
width laterally. 

Outcrop. The exposed portion of a vein on the surface. 

Panning. Washing earth or crushed rock in a pan, by 
agitation with water, to obtain the particles of greatest 
specific gravity it contains ; chiefly practised for gold, 
also for diamonds and other gems. 

Pay-streak. The thin layer of a vein which contains 
the pay-ore. 

Pinch. A contraction in the vein. 

Pit. A shallow shaft ; or, in some places, a vertical shaft 
at a coal mine ; or, loosely, a term applied to the coal-mine 
itself. 

Placer. A gravel deposit carrying gold or other 
mineral. 

Pocket. A single mass of ore which may be of any 
size. When a vein carries ore in isolated masses with 
much dead ground between them, it is said to be pockety. 

Poll Pick. A combination pick and hammer-head. 

Prop. A piece of timber or metal placed at right 
angles (or nearly so) to the roof or wall for its support. 



128 FIELD TESTING FOR GOLD AND SILVER. 

Prospect. A name given to a mineral location or to 
underground workings, the value of which has not yet 
been made manifest. A prospect is to a mine what 
mineral is to ore. 

Prospecting. The process of seeking pay-ore or pay- 
gravel, or the preliminary operations to test a discovery. 

Reduce. To deprive of oxygen ; also, in general to 
treat metallurgically for the production of metal. 

Reef. The outcrop of a hard vein projecting above 
surface. Also applied to auriferous quartz lodes or beds, 
particularly in Australia and Africa. 

Refractory. Resisting amalgamation ; difficult to treat. 

Riffle. A groove or interstice, or a cleat or block, so 
placed as to produce the same effect, in the bottom of a 
sluice, to catch free gold. 

Rim-rock. The bed-rock rising to form the boundary 
of a placer or gravel deposit. 

Roasting 1 . Calcination, usually with oxidation. 

Rocker. A short trough in which auriferous sands are 
agitated by oscillation, in water, to collect their gold. 

Roof. The stratum above a mineral bed. 

Rusty Gold. Free gold which does not easily amalga- 
mate, the particles being coated, as is supposed, with 
oxide of iron. 

Salting. Placing foreign ore in the crevices of a vein 
or elsewhere to fraudulently raise its apparent value. 

Seam. A layer of mineral. 

Selvage. See " Gouge." 

Sett or Set A frame of timber. 

Shaft A vertical opening from the surface. 




A FAULT WITH ' SLICKENSIDE' WALLS. 



To face p. 128 (after Diagram in outline). 



GLOSSARY OF MINING TERMS. 1 29 

Shode. See " Float." 

Slag. The vitreous mass separated from the fused 
metals in smelting ores. 

Slickenside. A polished and often striated surface in 
a vein or fault, or on its walls. 

Slope. An inclined shaft run down on a vein or dip- 
ping bed. It is an inside slope when it does not extend 
to the surface. 

Sluicing. Washing auriferous earth through long 
troughs (sluices). 

Stockwork. A mass of country rock so impregnated 
by veins that the whole must be mined together. 

Strike. The direction or bearing of any vein or stratum. 
The strike is at right angles to its dip. 

Stope. A step. The excavation of a vein in a series of 
steps. 

Stoping Overhand. Stoping upward, the flight of steps 
being reversed. 

Stoping Underhand. Stoping downward, so that the 
workings present the appearance of a flight of steps. 

Spoon. See " Horn." 

Stull. A stick of timber, or platform for supporting 
miners, or vein waste, temporarily or permanently, 

Sulphurets. In miners' phrase, the undecomposed 
metallic ores, usually sulphides. Chiefly applied to auri- 
ferous pyrites. 

Tailings. The waste from dressing of ore or washing 
of gravel. 

Tamping. Filling and ramming a bore-hole with clay, 
etc. 

Throw. The amount of dislocation of a stratum or 
vein measured vertically. 

I 



130 FIELD TESTING FOR GOLD AND SILVER. 

Tunnel. A horizontal passage, properly speaking one 
with both ends open to the surface, but it is applied to 
one opening at daylight and extending across the country 
rock to the vein or mine. 

Underlie. The inclination of a vein from the perpen- 
dicular, whereas dip is the inclination of a bed or vein 
from the horizon. 

Upraise. An auxiliary shaft, a mill-hole, carried from 
one level up toward another. 

Vein. A mineral deposit filling a fissure, or replacing 
more or less the walls of a fissure. 

Vug-, Vugg, or Vugh. A cavity in the rock, usually 
lined with a crystalline incrustation. 

Wall. The faces of a fissure ; the sides of a gallery. 

Whim. A hoisting appliance consisting of a pulley 
supporting the hoisting rope, which is wound on a drum 
turned by a horse attached to a beam. 

Whip. A hoisting appliance consisting of a pulley 
supporting the hoisting rope to which the horse is 
directly attached. 

Winch or Windlass. A small hoisting machine con- 
sisting of a horizontal drum operated by crank-arm and 
manual labour or by other power. 

Winze. An interior shaft usually connecting two 
levels. 

Workings. Any underground development from which 
ore is being extracted. 



COMMON ROCK-MINERALS AND ROCKS. 131 



COMMON ROCK-MINERALS AND ROCKS. 

Anticlinal. A fold of the rock or strata, convex upward. 

Augite. A mineral entering largely into the composi- 
tion of many traps and volcanic rocks. In composition it 
is closely allied to hornblende, but differs in the form of 
crystal, is less siliceous, and of greater specific gravity. 
Chief example of pyroxene. 

Bed. A layer seam or stratum of rock or mineral. 

Boulder. A loose mass of rock, usually more or less 
rounded, and larger than a pebble-stone or a cobble- 
stone, or say more than a foot in diameter. 

Boulder Clay. The stiff, hard, and usually unstratified 
clay of the drift or glacial period, which contains boulders 
scattered through it ; also called till, hard-pan, drift-clay, 
or simply drift. 

Calcite. Carbonate of calcium in a pure crystalline 
form. Limestone is an impure form of the same. A very 
common mineral. 

Chlorite. A soft, dark green mineral, entering largely 
into the composition of chloritic schist. It is a silicate of 
alumina, magnesia, and iron. 

Columnar. Resembling columns. The cliffs of trap- 
pean rocks or diabases have often a columnar structure. 

Conglomerate. A rock formed largely of rounded 
pebbles and stones, held together by a matrix or paste. 

Crystalline Rock. Rock consisting of crystalline par- 
ticles. When they are distinct, the rock is said to be 
coarsely crystalline. 

Diabase. Greenstone. Intrusive rock. Plagioclase 
felspar and augite. 



132 FIELD TESTING FOR GOLD AND SILVER. 

Diorite. Greenstone. Intrusive rock. Plagioclase fel- 
spar, generally with hornblende. 

Dolerite. A rock of the gabbro class, virtually the 
same as "Diabase" described above. 

Dolomite. A rock very like limestone, or in the pure 
state a mineral very like calcite, but composed of a mixture 
of the carbonates of calcium and magnesium. 

Dyke. A fissure in the earth's crust which has been 
filled with igneous matter. 

Felspars. Several allied species of minerals composed 
of silicates of alumina and of alkalies and lime. They 
crystallise in different systems. The triclinic group of 
felspars is called collectively plaglioclase ; the monoclinic 
group, orthoclase. 

Greenstone. A general name for the crystalline granular 
igneous rocks such as diorite, dolerite, diabase, basalt, 
etc. and a convenient term for use in the field where it 
is difficult to distinguish these rocks from one another. 
"Trap" has too wide a range of meaning. 

Gabbro. A crystalline basic intrusive rock, commonly 
with diallage as the augite member and a basic plagio- 
clase felspar. 

Gneiss. Metamorphic or altered rock. Minerals 
banded, giving bed-like structure, commonly quartz, 
felspar, and mica or hornblende. Unlike schist, does 
not split along laminae. 

Granite. Intrusive rock. Composed of quartz, felspar, 
and mica or hornblende. 

Hornblende. A very common mineral ; so called from 
its hornlike cleavage and its lustre. Usually dark green 
and blackish, but occasionally of light colours. 

Igneous. Connected with subterranean heat. Igneous 



COMMON ROCK-MINERALS AND ROCKS. 133 

rocks are those which have been once in a molten condi- 
tion. 

Joints. The division-planes which traverse nearly all 
rocks. Called " backs " by quarrymen. 

Lenticular. Shaped approximately like a double convex 
lens. When a mass of rock or quartz thins out from the 
centre to a thin edge all round it is said to be lenticular 
in form. 

Massive Rocks. Those which have no stratification 
or lamination, as greenstones, granite, syenite, etc. 

Metamorphic. Applied to rocks which have been 
changed in form and internal structure. Heat, pressure, 
and time acting on the constituents of rocks have been 
the main causes of metamorphism, converting ordinary 
and soft sediment deposits into crystalline and hard 
rocks. 

Olivine. A glassy-looking olive-green mineral occur- 
ring in many basic igneous rocks. 

Protogene. A variety of granite in which talc takes the 
place of mica ; so called by the French, who supposed 
that it was the first formed of the granites. The granites 
of Cornwall, England, which decompose and yield kaolin 
are of this kind. It is found in masses in the Seine River 
District in Canada, traversed by quartz veins carrying 
gold, iron, and copper pyrites, galena and zincblende. 

Porphyry. A rock with a felsitic or massive matrix or 
groundwork, and having distinct crystals in this matrix, 
commonly felspar crystals. 

Quartz. A common mineral, occurring in a great 
variety of forms. It is composed of the elements silicon 
and oxygen. It crystallises in the hexagonal system. 

Quartzite. A metamorphic rock, granular quartz. This 



134 FIELD TESTING FOR GOLD AND SILVER. 

term is generally applied to sandstones which have been 
indurated or altered by heat so as to assume the aspect of 
quartz rock. 

Schist. Foliated rock of crystalline character, which 
can be split along the laminae. According as one or 
other of the minerals are present, called mica schist, 
talc schist, chlorite schist, or hornblende schist. Felspar 
almost wanting. 

Serpentine. A compact rock, rather soft or sectile, with 
a conchoidal and splintery fracture and waxy lustre. 
When powdered, has a greasy feel. Capable of a high 
polish, and is called marble. In colour it has various 
shades of green, generally dark and leek green, often 
spotted or veined, or mottled with red. 

Shale. Laminated clayey rock, splitting with bedding. 

Slate. Hardened clayey rock, which splits readily into 
thin flakes. 

Syenite. Intrusive rock. Orthoclase felspar generally 
with hornblende. If some quartz is present, it is a quartz- 
syenite. 

Synclinal. A fold of the rock or strata, convex down- 
ward. 

Talc. A very soft mineral, being 1 in the scale of hard- 
ness. Occurs in laminae, like mica, but is not elastic. 
Has a pearly lustre and greasy feel. Prevailing colour, 
greenish. Enters into the composition of talcose schist, 
soapstone or steatite, the variety of granite known as pro- 
togene, etc. 

Trap. A general term for close-grained greenstones or 
igneous rocks. 

Volcanic. Pertaining to volcanoes. Volcanic rocks 
formed at or near the surface are lava, amygdaloid, and 
volcanic ash. 



APPENDIX. 



A. 

IN a large way gold and silver ores are usually treated in one of 
the following manners, and they may be divided into four main 
classes according to the manner in which they are metallurgi- 
cally treated, viz. : 

1. Those which contain copper enough to be smelted for 
copper, from which the gold and silver is extracted in the wet 
way. 

2. Those in which there is a large quantity of lead, which can 
be smelted for lead, and the gold and silver extracted from it. 

3. Free-milling ores, from which the precious metal can be 
extracted by mercury after being crushed by stamps, and ores in 
which there is neither copper or lead enough to allow of a 
process of smelting, but which can be treated in pans, these ores 
being "free-milling" if they require no metallurgical treatment, 
or "rebellious" if they have to be roasted with or without the 
addition of salt. 

4. Ores which do not contain enough either of lead or copper 
for smelting, which are poor both in silver and gold, contain 
large amounts of sulphur, arsenic, and antimony, and can only 
be treated by leaching with various solvents. 



136 FIELD TESTING FOR GOLD AND SILVER. 

B. 

Approximate 

NAME. Symbol Combin ing Weight 

or Atomic Weight. 

ALUMINIUM - - - Al 27 

ANTIMONY - - - - Sb 120 

ARSENIC AS 75 

BARIUM - - - - Ba 136-8 

BISMUTH - - - - Bi 207-5 

CADMIUM cd 112 

CALCIUM - - - - Ca 40 

Carbon c 12 

Chlorine Q 35-5 

CHROMIUM Cr 52.4 

COBALT - - - - Co 58-8 

COPPER Cu 63-5 

GOLD Au 197 

Hydrogen - H 1 

IRON ...... Fe 56 

LEAD - - . . . pb 207 

MAGNESIUM -.-".* .- Mg 24 

MANGANESE . - - Mn 54-8 

MERCURY - - - , Hg 200 

NICKEL - - - - Ni 58 

Nitrogen N 14 

Oxygen . . . Q 16 

Phosphorus p 31 

PLATINUM pt 195 

Silicon Si 28 

SILVER . . Ag 108 

SODIUM - - Na 23 

Sulphur s 32 

TIN Sn 118 

ZINC Zn 65 

(METALS are in CAPITAL letters.) 



INDEX. 



ACIDS, 75, 76 
Acre in sq. ft., 68 
Adit, 121 
Agate, 94 
Albite, 77, 94 
Alluvium, 121 
Aluminium, 90, 98, 136 
Amalgamation, 121 
Amphibole, 96 
Andesite, 114, 117 
Anglesite, 86 
Annealing, 25, 33 
Anorthite, 94 

Anthracite, 90 ; weight of, 69 
Anticlinal, 130 
Antimony, 82, 99, 136; with 

silver ore, 9 
Apatite, 76, 92 
Apex, 121 

Area and circumference, 68 
Argentiferous, 121 
Argentite, 8, 88 
Arrastra, 121 
Arsenic, 82, 99, 136; with 

silver ore, 9 
Asbestos paper, use of, in pan- 

amalgamation assay, 19, 20 
Ash, weight of, 69 
Assay defined, 122 
Assays, value of, in the field, 6 
Assaying with field furnace, 49 
Assay- ton, 39, 68 
Augite, 96, 113, 117, 130 
Auriferous, 122 
Azurite, 84 



BACKS or joints, 132 
Balance for small buttons, 
34, 58, 59, 60 ; hand-scale, 
23, 24, 27, 55 

Bar-diggings, 122 

Barium, 90, 99, 136 

Barytes, weight of, 69 

Basalt, 114, 117 

Bases of minerals, 75, 76 

Battery, 122 

Beauxite, 90 

Bed (in mineralogy), 131 

Bed-rock, 122 

Biotite, 96 

Bismuth, 82, 99, 136 

Bismuthinite, 82 

Bituminous coal, 69, 90 

Black sand, 5 

Black silver, 8 

Black's blow-pipe, 30, 31, 46 

Blast-bulb, 21, 46 

Blossom, 122 

Blow-out, 122 

Blow-pipe, 21, 22, 28, 31, 45 ; 
method of using, 21 ; assay 
for gold, 29 ; assay for 
silver, 43, 44, 45 ; re- 
actions, 98-108 

Bolt for making cupel, 22, 32 

Bonanza, 122 

Bone-ash, 22, 28, 61 

Borax, 92 

Borax glass, 21, 28, 30, 44, 55, 
62 

Bornite, 82 



138 



INDEX. 



Boron, 100 

Boulder, 131 

Boulder-clay, 131 

Bournonite, 86 

Breccia, 110, 116 

Brick, weight of, 69 

Brittle, sulphide of silver 

(stephanite), 8, 88 
Brown coal, or lignite, 90 ; 

weight of, 69 
Brown hematite, 84; weight of, 

69 
Brush, broad (varnishing), 12, 

27 ; small (camel's hair), 

30, 46; small (varnishing), 

52, 61 

Bullion, 122 ; bead, value of, 23 
Button-balance, Sargent's, 58 
Button brush, 62 ; pincers, 58, 62 

CADMIUM, 92, 100, 136 
Calamine, 90 
Calcedony, 94 

Calcination, 24, 26, 29, 30, 50 
Calcining, 122 
Calcite, 76, 78, 131 
Calcium, 92, 100, 136 
Cannel coal, weight of, 69 
Cap, cap rock, 122 
Capsule clay, small, for blow- 
pipe assay, 30, 34, 46 
Carbon, 90, 136 
Carbonates, 123 
Carnelian, 94 
Casing, 123 
Cassiterite, 77, 90 
Celestite, 92 
Cement, 123 
Cerargerite, 9 
Cerargyrite, 88 
Cerussite, 86 ; weight of, 69 
Chalcocite, 84 ; weight of, 69 



Chalcopyiite, 82 ; weight of, 6! 

Charcoal, 25, 26, 28 ; weight of 
69 

Characteristics of minerals, 77 

Chemical considerations, 75, 7C 

Chert, 94, 116 

Chlorides, 123 

Chloridise, 123 

Chlorination, 123 ; assay by, 6! 

Chlorite, 96, 111, 131 

Chlorite schist, 111, 116 

Chromite, 82 

Chromium, 82, 100, 136 

Chrysocolla, 84 

Chute, 123 

Cinnibar, 80, 86 

Circle, area of, 68 

Clay, 110, 116 ; weight of, 69 

Clay-pipe, 15, 22, 28 

Cleaning up, 123 

Clinometer, 123 

Coal, bituminous, weight ol 
69 ; cannel, weight of, 69 

Coal-oil, 49 

Cobalt, 31, 82, 100, 136 

Colour of minerals, 80 ; c 
igneous rocks, 115 

Columnar, 131 

Common ores, 82-92 

Compass, 27, 66 

Composition of minerals, 75, 7< 

Compound, 75 

Concentrated ores, testing, 45, 4 

Concentrates, 4, 35 ; calcinin 
of, 24, 29, 30 ; determina 
tion of, by measuring c 
weighing, 29 ; estimatin 
proportion! of, in ores, 18 
fluxes to smelt after roasting 
25 ; qualitative results fror 
blow-pipe test, 25; smelting 
24 



INDEX. 



139 



Concentration, 123 
Conglomerate, 110, 116, 131 
Copper, 31, 33, 82, 84, 100, 

136 

Cost of treatment, 2 
Country, country rock, 123 
Cradle, 123 
Crucible for blow-pipe assay, 

30, 46 
Cryolite, 90 
Crystalline rocks, 131 
Crystallisation, systems of, 77 
Cupel, 22, 56, 61 
Cupel and lead button tongs, 

62 
Cupellation, 22, 33; in field 

furnace, 56 
Cuprite, 76, 84 
Cyanide extraction, 124 
Cyanide test, 64, 65, 66 



DEAD-ROASTING, 124 
Deposit, irregular, 124 
Diabase, 113, 117, 131 
Diallage, specific gravity of, 80 
Diorite, 113, 117, 132 
Diorite-porphyry, 114, 117 
Dip, 124 
Ditch, 124; to find area of 

section of, 71 
Dolerite, 113, 117, 132 
Dolomite, 77, 92, 116, 132 
Drift, 124 
Dump, 124 ; hydraulic washing, 

72 
Dyke, 132 



CLEMENTS of minerals, 75, 

JL/ 136 

Erythrite, 82 



FACE, 124 
Fault, 124 
Feeder, 124 
Felsite, 114, 117 
Felspar, 76, 78, 94, 132 
Field furnace, assaying with, 49 ; 

procedure in using, 50-57 ; 

charges for, 53 ; starting 

blast and scorifying, 53, 54 ; 

smelting in pot, 55 
Field tests, 2, 6 
Fines (pulverised ore), 1 1 
Fletcher's furnace, 30 
Flint, 94, 116 
Float, 124 
Flouring, 125 
Flucan, 125 
Flume, 125 ; to find area of 

section of, 71 
Fluor-spar, 77, 78 
Fluorine, 101 
Flux, 125 ; for blow- pipe assay 

for gold, 30 ; for blow-pipe 

assay for silver, 43 ; for 

cleaning gold sponge, 21 ; 

for testing purity of lead, 61 
Foot-wall, 125 
Franklinite, 86 
Free, 125 
Free gold, 1 
Free milling, 135 ; testing outfit 

for, 27 
Free-milling gold ores, 1 ; usual 

test of, 2 
Freezing in cupellation in field 

furnace, 61 
Furnace, see Field furnace ; 

Fletcher's, 30 ; Sargent's, 

49 

Fuse, 125 
Fusion in the blow-pipe furnace, 

30, 31 



140 



INDEX. 



ABBRO, 113, 117, 132 

Galena, 5, 75, 86, 179 ; 
weight of, 69 ; weight of 
vein of, 68 ; specific gravity 
of, 79 

Gangue, 125 

Gersdorffite, 88 

Gneiss, 110, 111, 116, 132 

Gold, ores of, 84 ; occurrence 
of, 1 ; free-milling, 1 ; re- 
fractory, 1 ; blow-pipe re- 
actions with, 101 ; symbol 
of, 136 ; estimating quantity 
from panning, 4 ; float, 8 ; 
leaf, 8 

Gold nuggets, cleaning, 71 

Gold, pure weight of, 69 

Gold sponge, cleaning of, 20 

Gossan, 125 

Gouge, 125 

Gramme, 68 

Granite, 69, 110, 112, 117, 132; 
graphic, 116; specific gravity 
of, 80 

Granulite, 116 

Graphic granite, 116 

Graphite, 90 

Grass roots, 125 

Gravel, auriferous, treatment of, 
68 

Grease-pot, or miner's candle, 21 

Greenockite, 92 

Greenstones, 113, 132 

Greisen, 116 

Grey copper ore, 8 

Gypsum, 76, 92 

HAMMER for small buttons, 
22, 28 large, for rock, 
etc., 11, 55, 56, 62 
Hanging wall, 126 
Hardness, scale of, 78 



Heave, 125 

Hematite, 76, 77, 80, 84 ; weight 

of, 69 ; specific gravity of, 

79 

Hessite, 9, 88 

Horn, 15, 67, 126 ; silver, 9 
Hornblende, 111, 113, 132 ; 

schist, 111, 116 
Horse (in mineralogy), 126 
Hungry (in mineralogy), 126 
Hydraulic mining, 126 ; notes 

on, 70, 71 

IGNEOUS rocks, 110, 112- 

1 115, 117, 132 

Inquarting, 56 

Iodine, 102 

Iron, 31, 84, 86, 102, 136; 
rolled, weight of, 69 

Irregular deposit, 124 

Ivory scale (Plattner's), use of, 
36-42 ; for measuringbuttons 
of gold and silver, 29, 31, 
33, 34, 35, 36, 37, 38, 39, 
40, 41, 42, 43, 44, 46, 57, 
58, 59, 60 

TASPER, 94 
J Joints or backs, 133 

KAOLIN, 94, no, ne 

T ABRADORITE, 77, 64 

L Laccolite, 112 

Lagging, 126 

Lead, 86, 103, 136 ; weight of, 
69 

Lead button, in pan-amalgama- 
tion assay, 23 ; in blow- pipe 
assay, 33 

Lead, with silver ore, 9 



INDEX. 



141 



Lead and borax measure, 53, 61 

Lenticular, 133 

Level, 126 

Light red silver ore, 8 

Lignite, weight of, 69 

Limestone, 110 ; weight of, 69 

Litharge, 28, 30, 55, 62 

Lithium, 103 

Lixiviation, 126 

Lode, 126 

Long Tom, 71 

Louis, Henry,on "Gold-milling," 

2 

Low grade ores, 31, 32, 45, 46, 
Lustre, 80 

MAGNESIUM, 103, 136 
Magnet, 12, 28, 31, 51 

Magnetite, 5, 76, 84; weight 
of, 69 

Malachite, 84 

Manganese, 86, 103, 136 

Maicasite, 86 

Marble, 110, 116 

Massive rocks, 133 

Mercury, 27, 86, 104, 136; 
cleaning, 17 ; loss of, 
through flouring, 18; weigh- 
ing out, 15 

Mercury retort, 19, 20, 28 

Metallics, 29, 51, 52 

Metamorphic, 133 

Metre, 68 

Mica, 77, 94, 110, 111, 112 

Mica schist, 111, 116 

Millerite, 88 

Mill-run, 126 

Mine, definition of, 77, 126 

Mineral, definition of, 126 

Minerals, characteristics of, 75-80 

Miner's candle, or grease-pot, 21 

Miner's inch, 68, 126 



Mispickel, 82 
Mixing cloth, 11, 27, 48 
Molybdenite, 92 
Molybdenum, 92, 104 
Mortar, iron, 2, 27, 48 
Mould for field furnace, 55, 62 
Muscovite, 94 

VT ICCOLITE, 69, 88 

IN Nickel, 33, 88, 104, 136 

Nickel glance, 88 ; weight of, 69 

Nitre, 43, 46, 92 

Nitric acid, 19, 23, 25, 27, 33 

Nugget, 127 

OAK, weight of, 69 
Obsidian, 114, 117 

Olivine, 96, 113, 114, 117, 133 

Onyx, 94 

Ore, definition of, 81, 127 

Ore shoot, 127 

Ores, table of, 82-93 ; manner of 
using it, 81 

Orthoclase felspar, 78, 94, 110, 
111, 112, 113, 117, 132 

Ounce, avoirdupois, 68 ; troy, 68 

Outcrop, 127 

Outfit for gold-milling testing, 
27 ; for blow-pipe assay, 
46 ; for assaying, 61 ; for pan- 
amalgamation, and blow- 
pipe assay, 48 ; (personal) 
for prospector, 67; "free- 
milling" gold ore, 27,28 

PACK, 66, 67 
Pack-horse, 66, 67 
Pan-amalgamation assay for 
gold, 15-26 ; for silver, 43, 
44, 45 

Pan, salted, 3 
Panning, 2, 127 



142 



INDEX. 



Panning assay, 14, 15 ; gravel, 4 

Panning-out concentrates, 18 ; 
mercury, 17 ; pulverised 
quartz, 3 

Parting, 23, 31, 33, 57 

Pay-streak, 127 

Peridotite, 114, 117 

Pestle, wooden, 15, 16, 28 

Petzite, 2, 84 

Phlogopite, 96 

Phosphorus, 104, 136 

Pinch, 127 

Pine (white and yellow), weight 
of, 69 

Pit, 127 

Placer, 127 ; gold, 1 

Placer ground, weights of, 70 ; 
amount of gravel a man 
can wash daily, 71 

Placer mining, 70, 71 

Plagioclase felspar, 94, 113, 117, 
132 

Platinum, 88, 104, 136 

Plattner's ivory scale, use of, 9, 
41, 42 

Pocket, 127 

Poll-pick, 66, 127 

Polybasite, 9, 88 

Porcelain dish, 15, 19, 28; 
thimble, 23, 28 

Porphyry, 114, 117, 133; 
weight of, 69 

Potassium cyanide, 16 

Pot for field furnace, 55, 61 

Pound, avoirdupois, 68; troy, 68 

Prop, 127 

Prospect, 128 

Prospecting, 128 

Prospector's outfit, for free- 
milling testing, 27; for 
blow-pipe assay, 46 ; for 
assaying, 61 ; personal, 67 



Protogene, 133 
Proustite, 8, 88 
Pulp, 2 

Pyrargyrite, 8, 80, 88 
Pyrites, 5, 84 ; weight of, 69 
Pyrolusite, 86 
Pyromorphite, 86 
Pyroxene, 77, 96, 113, 130 
Pyroxenite, 79 
Pyrrhotite, 86 

/QUALITATIVE deter 
\^J mination of ores, 5 
^ Quantitative determina 

tion of ores, 5 
Quartering, 11 
Quartz, 76, 77, 78, 79, 94, 133 

weight of, 69 ; broken 

weight of, 68 ; specifii 

gravity of, 79 
Quartz felsite, 114, 117 
Quartzite, 110, 116, 133 

RAKE, 61, 62 
Rebellious ores, 9, 45 

Reduce, 128 

Reef, 128 

Refractory, 128 

Refractory ores, 1 ; determina 
tion of, by measuring o 
weighing, 29 ; iron ladl< 
for roasting, 26 ; values of 
estimated by difference, 42 

Results, from blow-pipe assay 
34 ; from pan-amalgamatioi 
and blow-pipe assay, 35 
from a free-milling ore, 26 
from pan-amalgamation tes 
of ore, and blow-pipe assa^ 
test of concentrates, 26 

Rhodocrosite, 86 

Rhyolite, 114, 117 



INDEX. 



143 



Rich leads, 31, 34 

Riders, with button balance, 58, 

59, 60 
Riffle, 128 
Rim-rock, 128 
Roasting, 128; of concentrates, 

26, 30, 50; of refractory 

ore, 26, 29, 30, 50; of 

silver ore, 9 

Rock-forming minerals, 94-97 
Rocker, 71, 128 
Roof, 128 
Rubber-cloth, 61 
Ruby silver, 8 
Rusty gold, 128 

SALTING, 128 
Salt for assays, 30, 45, 46, 
62 

Salts, minerals as, 75, 76, 92 

Sampling, 6, 29, 51, 52; de- 
tailed instructions as to, 10 

Sand, auriferous treatment of, 
6, 8 

Sandstone, 110, 116 ; weight of, 
69 

Sargent's button balance, 48; 
portable furnace, 49 

Schists, 110, 111, 116, 134 

Scorifier tongs, 54, 62 

Scorifiers, 53, 61 

Scorifying, 32, 53 

Seam, 128 

Sett, or set, 128 

Selvage, 128 

Serpentine, 96, 111, 116, 134 

Shaft, 128 

Shales, 110, 116, 134 

Shode, 129 

Siderite, or spathic iron ore, 77, 
86 

Silicates, 76 



Silicon, 76, 105, 136 

Silver, 88, 90, 105, 136 ; weight 

of, 69 ; native, 8, 69, 88 ; 

blow-pipe assay, 43, 44, 45 ; 

pan-amalgamation assay, 

43, 44, 45 

Silver-foil, 23, 28, 31 
Silver ore, common forms of, 8 ; 

most convenient test of, 9 ; 

pan-amalgamation of, 91 
Silver-lead, 8 
Slag, 31, 54, 55, 129 
Slates, 110, 116, 134; weight 

of, 69 

Slickenside, 129 
Slimes, 3 
Slope, 129 
Sluice, 71, 72 
Sluicing, 129 
Smaltite, 82 
Smelting ores, estimating of, by 

blow-pipe assay, 29-48 ; in 

pot field furnace, 55 
Smithsonite, 90 
Soda, bi-carbonate of, 28, 30, 

55, 62 

Sodium, 27, 92, 107, 136 
Sodium amalgam, making, 15 ; 

mixing pulp with, 15 
Sodium bi-carbonate, 3 
Sorting ore, 7 
Spathic iron ore or siderate, 77, 

86 
Specific gravity of minerals, 79 ; 

of igneous rocks, 115, 117 
Specular iron ore, 84 ; weight 

of, 69 

Spill of lead in muffle, 61 
Sponge, gold, 19 
Spoon (in mineralogy), 129 
Stephanite, 8, 88 
Stibnite, 77, 82 



144 



INDEX. 



Stockwork, 129 

Stope, 129 

Sloping, over- or under-hand. 

129 

Streak, 80 

Stream, velocity of, 72 
Strike, 129 
Stiomeyerite, 90 
Strontianite, 92 
Strontium, 92, 107 
Stull, 129 
Sugar, 67 

Sulphur, 92, 107, 136 
Sulphurets, 129 
Syenite, 113, 117, 134; weight 

of, 69 

Sylvanite, 2, 84 
Synclinal, 134 



TABLE of common ores, 82- 
93 ; manner of using it, 

81 

Tailings, 4, 129 
Talc, 78, 96, 111, 116, 134; 

schist, 111, 116 
Tamping, 129 
Telluric silver, 9 
Telluride gold and silver ores, 

assay of, 62 

Tellurides of gold and silver, 2 
Tellurium, 107 
Tetradymite, 82 
Tetrahedrite, 8, 84 
Throw, 129 
Timber, weight of, 68 
Tin, 31, 90, 107, 136 
Titanium, 108 
Ton, long and short, 68 
Topaz, 78 
Tourmaline, 80 
Trachyte, 114, 117 



Trap, 134 
Tungsten, 108 
Tunnel, 130 



u 



NDERLIE, 130 
Upraise, 130 



VEIN, 130 
Volcanic, 134 
Vug, vugg, or vugh, 130 



WAD, 86 
Wall, 130 

Water, presence of, in mineral, 
108 ; moving power of, 70 ; 
temperature of, for pan- 
amalgamation assay, 17 ; 
weight of, 70 ; measuring 
in streams or ditches, 71 

Weighing, gold button, 23, 24, 
57, 58, 59, 60 

Weighing out charge, 29, 30, 
52, 53 

Weights for field furnace, 55, 61 

Whim, 130 

Whip, 130 

Winch, 130 

Windlass, 130 

Winze, 130 

Witherite, 90 

Wood-ashes, use of, with retort, 
19 

Workings, 130 



ZINC, 90, 108, 136 
Zinc blende, 90; weight 
of, 69 
Zincite, 90 



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