AGATE

Physical Properties and Origin

BY
OLIVER C. FARRINGTON

CURATOR OF C.wOLOGY

Archaeology and Folk-lore

BY
BERTHOLD LAUFER

CURATOR OF ANTHROPOLOGY

—

NATURAL
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‘A, FOUNDED BY MARSHALL FIELD QZ

GEOLOGY

LEAFLET 8

FIELD MUSEUM OF NATURAL HISTORY
CHICAGO
1927

LIST OF GEOLOGICAL LEAFLETS ISSUED TO DATE

No. 1. Model of an ArizonaGold Mine. . . . . . $.10
No. 2. Models of Blast Furnaces for Smelting Iron )
No. 3. Amber—Its Physical Properties and
Geological Occurrence . . . .
4.) Meteorites iis i Vins ccaie (Bee age
5. SOUS Speier cae eae ede he
6. Lhe Mloone pea: By Ma sey dbra agg SeyS
No. 7. Early Geological Easton of Chicago . .
3
9

. . . . . .

Apale reuse inelitens cimohtes un ei ie
Me HownoldvarevHossilsanetsae | ee wens

FIELD MUSEUM OF NATURAL HISTORY
CHICAGO, U.S.A.

LEAFLET 8. PLATE |.

“FORTIFICATION’’ AGATE. URUGUAY.
ARTIFICIALLY COLORED.

FIELD MUSEUM OF NATURAL HISTORY
DEPARTMENT OF GEOLOGY
CHICAGO, 1927

LEAFLET NUMBER 8

Agate—Physical Properties and Origin

Agate is a variety of chalcedony chiefly distin-
guished by its banded or variegated structure and col-
oring. Its banded appearance is due to the fact that
it is made up of a great number of exceedingly thin
layers which appear as bands in cross section. As
seen by the naked eye, these bands differ considerably
in width, some seeming no wider than a line, while
others may be a quarter to a half inch wide. In real-
ity, all these bands are made up of still finer ones, the
individuals of which can be seen only with a micro-
scope. In a section of agate only one inch in thick-
ness, Sir David Brewster counted 17,000 such individ-
ual bands, and this number is probably representative
of their abundance in most agates. In all agates the
layers are composed of minute fibers or microscopic
crystals standing at right angles to the course of the
bands. Agate is generally semi-transparent rather
than opaque but the layers may differ considerably in
this respect and some be quite opaque. These differ-
ences in translucency correspond to variations in por-
Osity, as is shown by the fact that whereas the trans-
lucent layers absorb coloring matters readily, the
opaque layers are little penetrated by them. As to the
average size of these pores in agate, it is known that
the diameter of the pores of water-rich silica colloids
(jellies) is about one five-millionth of a millimeter,
and those of agate (which is silica without water)

[105 ]

2, FIELD MUSEUM OF NATURAL HISTORY

are probably smaller, as removal of the water tends
to contract them. The pores of agate are too small
to admit the absorption of large molecules like those
of sugar or they admit them only with difficulty. This
is shown by the fact that in the process of coloring
agates black by means of a sugar solution and sul-
phuric acid, from two to three weeks are required for
the large sugar molecules to penetrate the agate, while
only a few hours are necessary for the absorption of
the smaller molecules of sulphuric acid.

Owing, probably, to the fibrous structure and dens-
ity of agate, it is tough and remarkably resistant to
wear. It is somewhat harder than quartz. These qual-
ities make it useful for many industrial purposes.
Chemically, agate is pure silicon, the commonest com-
ponent of the earth’s crust. Of agates it may be said
more truly than of other minerals, perhaps, that each
individual is unique; one does not duplicate another.
But although agates vary greatly in pattern and in
color, yet they fall into certain natural groups based
chiefly on pattern, which permit them to be given
a certain mineralogical classification.

The most common and characteristic form of
agates is one which in cross section resembles an old-
time bastion, a defensive work characterized by curv-
ing contours and salient angles. Agates of this pattern
are known as “fortification” agates (Plate 1). Those
agates in which the bands run approximately straight,
are known as “ribbon” agates. This kind of band-
ing is also characteristic of onyx and hence agates
of this kind are sometimes known as “onyx” agates.
Both patterns can sometimes be seen in the same
agate (Plate IV). If the bands lie so close together
that a ray of light in passing through them is broken
up into prismatic colors, it distinguishes what are
called “rainbow” agates. If the agate is irregularly

[ 106 ]

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AGATE—PHYSICAL PROPERTIES AND ORIGIN 3

and obscurely colored, it is called a “clouded” agate.
In the so-called ‘‘eye” or “ring” agates the bands run
in concentric circles. Agates made up of fragments
of former agates cemented together are known as
“ruin’’ agates (Plate IV). Characteristic agates of
this kind are found in Schlottwitz, Saxony. Agates
appearing to be made up of tubes or pipes cemented
together are known as “pipe” agates. An important
variety of agate is that known as “moss” agate, in
which, as the name indicates, the agate has the ap-
pearance of containing inclusions of moss (Plate V).
These inclusions are often arranged in such a manner
as to give the appearance of a miniature landscape,
in which case they are known as “landscape” agates
(Plate VI).

Agates are generally formed in cavities in volcanic
rocks. In the escape of gases and vapors from such
rocks on cooling, cavities similar to those seen when
pasty substances are heated are often formed and re-
main open when the rock has cooled. The cavities
are usually spheroidal in form or, more specifically,
are often shaped like an almond, whence the term
amygdaloidal, from the Greek word for almond, is ap-
plied to them. The size of these cavities is also often
about that of the almond but they may be much larger.
It is in cavities like these that agates are chiefly
formed, occurring as a filling that takes the shape of
the cavity. Being of very tough material, which re-
sists both physical and chemical corrosion, the agate
nodules (the lumps or masses formed by the filling of
the cavities) are usually left intact after the rock
about them has decomposed and hence agates are
often found in soil or in beds of streams. In the lat-
ter case they may occur far removed from the place
of their origin. The size of the agate nodules varies
according to the size of the cavity in which they are

[ 107]

4 FIELD MUSEUM OF NATURAL HISTORY

formed. From very minute, they run up to weights as
high as 4,000 pounds.

Although most agates are formed in the cavities
of volcanic rocks, some are formed in other cavities,
such, for instance, as those left by the decay of wood.
The siliceous linings of rock fissures sometimes also
have the structure of agate. The so-called agate nod-
ules are not always composed entirely of agate. Fre-
quently, quartz crystals or other forms of quartz or
even other minerals line the interior of the nodules,
or are interpolated with the layers.

OCCURRENCE OF AGATES

Agates are found in many parts of the world, be-
ing likely to be formed wherever there are trap’ rocks.
As already noted, decay of these rocks leaves the more
resistant agate nodules in the soil, from which they
are often distributed by streams.

Agates resulting from the decomposition of the
trap of the Deccan plateau in India have been gathered
for thousands of years. After more or less fashioning
by native lapidaries they have found their way to Eu-
ropean and Oriental markets. A further description of
this industry will be found in subsequent pages. The
principal European locality for agates is in south-
western Prussia in the region of the Nahe River, a
tributary of the Rhine. Not only has the agate found
in this region been worked for centuries, but the vari-
ous processes of shaping and coloring it, have been so
fully developed there that it is now the world center
of the agate business. Among other European locali-
ties, the so-called Scotch pebbles from Forfarshire
and Perthshire in Scotland furnish attractive agates.

The most extensive ocurrence of agate known at
‘Trap. A common name for any dark, finely crystalline, ig-

neous rock.
[ 108 ]

LEAFLET 8. PLATE

AGATE-LIKE BANDING PRODUCED BY DIFFUSION IN GELATINE.
*"LIESEGANG’S RINGS’’

AGATE—PHYSICAL PROPERTIES AND ORIGIN 5

the present time is in the mountain chain extending
from Porto Alegre, State of Rio Grande do Sul, in
Brazil, to the district of Salto in northern Uruguay.
The agates of this region surpass in size and beauty
any others known and they form at the present time
the principal source of supply of agates for commer-
cial purposes.

A portion of the agate-bearing area in Uruguay
was visited in 1926 by Associate Curator H. W. Nich-
ols of the Museum on the Captain Marshall Field
South American Expedition of that year. Mr. Nichols
reports that the agates are dug from shallow pits in
grazing lands, where they occur in considerable quan-
tity. Associated with the agates are many hollow
stones which are often lined with amethyst crystals.
Some of these are of gem quality. Pieces of agate are
also found in the stream beds of the region, fresh sup-
plies being brought down by floods. The largest dig-
gings at present are in the Catalan district of Artigas,
Uruguay, which is about one hundred miles north of
Salto.

Agates of considerable beauty, though not of great
size, are found in many places in the United States.
Those of Agate Bay, Lake Superior, have rich colors
and make attractive charms and other ornaments.
Agates are found in the beds of many streams in
Colorado, Montana and other regions of the Rocky
Mountains. They occur all along the Mississippi River,
especially in Minnesota, also along the Fox River in
Illinois, in the trap rocks bordering the Connecticut
River and on the coasts of California and Oregon.

METHOD OF FORMATION OF AGATE

No one who gives much consideration to the sub-
ject of agates, can fail to be impressed with the difficul-
ty of explaining how they are formed. They appear to

[109 ]

6 FIELD MUSEUM OF NATURAL HISTORY

be made up of successive layers deposited on the walls
of the interiors of cavities, each layer toward the in-
terior being younger than the one preceding. Some-
times the process of deposition appears to have con-
tinued until the cavity was entirely filled, but in other
cases a vacancy still remains at the center. If the
above is the method of formation, it is difficult to un-
derstand why the deposition of the first layer, or, at
least of the first two or three layers, would not close
the cavity to succeeding deposits.

Various attempts have been made to answer this
question. Haidinger, a German geologist, writing
about 1849, made the suggestion that the moisture
ordinarily found in rocks, the so-called “‘mountain
moisture” would “sweat” through into the cavities and
that successive solutions of silica would thus enter
through diffusion. This explanation seemed adequate
to many investigators, but others have agreed with
Noggerath, a contemporary of Haidinger, that it is
doubtful if solutions would continually enter the cavity
in this manner, especially as the outer layers of agate
nodules are known by agate cutters to be particularly
hard and impervious to liquids. As a better explana-
tion Noeggerath called attention to an apparent canal
or conduit which can be seen leading outwards from
the interior of most agates and which he believed re-
mained open during the formation of the agate for the
admission of percolating waters. Such a channel is
shown in Plate II. In some agates several such so-
called entrance canals are to be seen, but in some,
unfortunately for the theory, none can be found.
Moreover, it is difficult to understand why such canals,
if they ever existed, would remain open. The above
theories, however, are the only ones that until recently
have seemed at all worthy of credence as possible ex-
planations of the manner of formation of agates and

[ 110 ]

LEAFLET 8. PLATE IV,

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at:
»

‘“FORTIFICATION’’ AGATE WITH LAYERS IN TWO DIRECTIONS.

“*RUIN’’ AGATE.

AGATE—PHYSICAL PROPERTIES AND ORIGIN if

for many years were accepted by most investigators.
The theory is stated by Bauer in a complete form as
follows: ‘To explain this phenomenon [the forma-
tion of agates] the existence is assumed of hot, inter-
mittent springs, such as are now seen to perfection
in the geysers of Iceland and in the United States
National Park on the Yellowstone River. The essen-
tial condition is that the hot or warm water rising
up from the depths shall saturate the rocks, and that
it shall sink again, leaving the rocks dry for a period.
The hot water dissolves out the silica and other con-
stituents of the rock and the solution fills up the
amygdaloidal cavities. When the waters sink, these
cavities are emptied, only a film of water covering
their walls being left behind. On the evaporation
of this film, which readily takes place at such a high
temperature, a thin layer of silica is deposited on the
walls of the cavity. When the hot spring again rises,
the same thing takes place and a second layer of silica
is deposited, and so on, until the cavity is more or less
completely filled up. Each time, the fluid passes into
and out of the cavity by the canals, which are for
this reason often referred to as tubes of entry or
escape. The fluid, also, perhaps, passes to a certain
extent through the porous agate itself. Crevices, fis-
sures, and other cavities in the rock are, of course,
filled with agate in the same way.”

It is only recently that a theory for the formation
of agates has been proposed which gives a totally
different explanation from the above and which is in
many respects more satisfactory than the earlier views.
According to the later theory, the rock cavity in which
the agate is formed, first becomes more or less filled
with silica in a colloidal (jelly-like) condition. In such
a colloid a banded structure can be produced by proc-
esses which can be illustrated with ordinary gelatine.

Eah ey)

8 FIELD MUSEUM OF NATURAL HISTORY

The following experiment as described by Ostwald
in 1896 illustrates this process. If silver nitrate is
introduced into a colloid which contains ammonium
bi-chromate, silver chromate (a red salt) is at once
formed, but it does not at first appear in a solid form.
It is still dissolved. Gradually, however, through the
continual formation of silver chromate, the solution
becomes so concentrated that it must somewhere sep-
arate out. This separation takes place first at an edge.
Then all the super-saturated substance makes its way
to this edge and likewise separates out. An essential
consequence of this is that adjacent to this deposit
a zone is formed which is free from silver chromate.
But this zone also does not contain ammonium bi-
chromate, for this has been used up by the silver ni-

Ir g

Fig. 1. Origin of banding in colloids.

trate. Here, then, no new silver chromate can form
and the zone becomes colorless. The excess of silver
nitrate pushes on, however, and by the same reactions
forms a second band of silver chromate and a color-
less zone. Continuation of this process gives a banded
structure.

The process is illustrated diagramatically in Fig. 1.
The areas colored yellow represent a mass of gelatine
which contains ammonium bi-chromate. In a, the
light-red area at the top represents a zone of dis-
solved silver chromate. In b, the dark-red edge shows

[112]

LEAFLET 8. PLATE V.

MOSS AGATE. CHINA.

IMITATION OF MOSS AGATE.
PRODUCED BY ADDING IRON VITROL TO WATER GLASS.

Coe

Imitation of Moss Agate. The word

“vitrol’’ should read ‘‘vitriol.’’

ERRATUM—Plate V.

U}

AGATE—PHYSICAL PROPERTIES AND ORIGIN 9

the beginning of the formation of a zone of precipi-
tated silver chromate. To the neighborhood of this
zone as shown in ¢, all the super-saturated silver
chromate wanders, leaving a colorless area. But be-
low the chromate-free area a new zone of dissolved
silver chromate has formed as shown in d. Ere this
has had time to pass to the zone of deposit, its con-
centration has become so high that within its own area
deposition takes place as shown in e. By the gather-
ing of the super-saturated silver chromate at this edge,
a second, colorless zone is formed as shown in f. Sim-
ilarly, a third zone of deposit is formed as shown in g
and so the process goes on until a series of bands is
produced. These bands are parallel to the original
outline of the colloid and are of wonderful regularity.
Their appearance is marvellously like that of the bands
of a fortification agate. An example of banding pro-
duced in this way is shown in Plate III.

Besides explaining the banding, this view of the
method of formation of agates also indicates why agate
nodules are often hollow in the interior. Drying of
the colloidal silica causes a shrinking in bulk which
would often leave such a hollow. The theory also
explains the frequent occurrence of quartz crystals at
the interior of agates. Crystals cannot form in col-
loids on account of surface tension, but when the ten-
sion is relieved at the hollow interior of the nodule,
complete crystallization can take place there.

Anyone wishing to illustrate for himself the for-
mation of the bands referred to can readily do so by
making the following experiment: Dissolve 3 grams
of gelatine in 60 c. c. of water, add 3 drops of a 5%
citric acid solution and 4 drops of a 10% ammonium
bi-chromate solution. Stir the liquid and pour some
of it on a clean glass plate. Allow it to harden for
one to two hours. Then with a glass rod that has been

[ 113 ]

10 FIELD MUSEUM OF NATURAL HISTORY

dipped into a 25% solution of silver nitrate draw a
band of silver nitrate about the outer edge of the gela-
tine. Put the plate in a cool, dry place not exposed
to sunlight and watch the course of the reaction.
Gradually the silver nitrate will penetrate the gela-
tine and the formation of bands of silver chromate
will begin. The process will continue and bands be
formed for 24 to 48 hours or until the silver nitrate
and ammonium bi-chromate have exchanged positions,
the silver nitrate ultimately reaching the center of
the plate and the ammonium bi-chromate the circum-
ference.

The formation of bands of this sort was first made
known by a German chemist, Raphael Ed. Liesegang,
and the phenomenon is now generally known as “‘Liese-
gang’s rings.” The width of the bands and other
features can be varied by using other percentages of
chemicals than those given here and other chemicals.
Then too, by varying the points of application of the
silver nitrate or by introducing it as drops or lines,
imitations of other patterns seen in agates can be
obtained.

According to the present view, then, fortification
or common agates originate from a filling of hollow
spaces in rocks by a silica colloid (jelly), within which
an iron compound has been rhythmically deposited.

Although the banding of fortification agates can
be acceptably explained by the introduction of iron
salts into colloidal silica, it is at first sight difficult to
see how moss and pipe agates and some other forms
can be accounted for in this way.

For a long time and even in mineralogical text
books up to the 19th century it was thought, and stated,
that moss agates were made up of moss enclosed in sili-
ea. Peculiar enclosures in some other kinds of agates
were also explained as petrifications of other once living

[114]

12 FIELD MUSEUM OF NATURAL HISTORY

In this way the forms known as pipe agates are sup-
posed to originate.

NATURAL COLORS OF AGATES

While the majority of agates are colorless in their
natural state, some natural colors do occur. Red and
brown are the most common and are due to a content
of iron oxide. If the color is brown, iron hydroxide
is the coloring matter, if red, iron oxide. The red
color is usually produced by alteration of the brown,
loss of water by exposure to sun’s heat forming the
oxide from the hydroxide. In agates with straight
bands these colors form the layers of sard and car-
nelian so much used for cameos. Another color na-
turally occurring is black. It rarely occurs massive,
usually appearing as scattered flakes. Oxidation often
causes this to change to red or brown, usually in spots
or along clefts. Green is a color often seen in the moss
agates and adds to the impression that these agates
contain real moss. It is now well known, however,
that the moss-like appearance is not due either in color
or form to moss. As already noted, green, fibrous in-
clusions can be produced in water-glass, the colloidal
form of silica, by introducing iron vitriol. Thread-
like and moss-like forms may then appear as shown
in Plate V. Whether the green fibers of moss agates
are of this nature or consist of some fibrous mineral
such as hornblende or chlorite is not certain. Perhaps
both modes of origin occur.

ARTIFICIAL COLORING OF AGATES

Nearly all agates that one sees in use nowadays
have been artificially colored. While the possibility of
coloring agates artificially has been thought to have
been known to the Romans, and as having been men-
tioned by Pliny, it is shown by Dr. Laufer in the later

[116]

BEAGLE S: PLATE VII.

SECTION OF AGATE.

SHOWING NATURAL COLOR AT THE UPPER END AND ON THE REMAINDER
VARIOUS ARTIFICIAL COLORS.

AGATE—PHYSICAL PROPERTIES AND ORIGIN 13

pages of this leaflet that this view is incorrect. At any
rate modern methods of coloring agates were not intro-
duced until 1819, when a method of coloring black was
accidentally discovered in Germany. Production of a
red color by burning was to be seen in nature, since
one could there observe that portions of agates pro-
truding from the earth were reddened as compared
with the covered portions. This natural process was
at first imitated by exposing agates to the heat of the
sun, but later the same result was obtained more
quickly by heating the stones in ovens. It being
found, however, that some stones would not color in
this way, it was concluded it was because they con-
tained no iron compounds. Accordingly experiments
were made to introduce iron compounds into the stones,
and the colors were then successfully obtained. Hav-
ing succeeded in this, the production of other colors
was sought. In 1845 a method of coloring blue was
discovered and in 1853 one of coloring green. Dreher
in his book on the coloring of agates gives the follow-
ing table of colors which can be produced in agates
and the methods of producing them :—

DESIRED COLORING HOW
COLOR MATTER OBTAINED

Red Iron oxide From iron nitrate by heating.

Bluish-green Chromic oxide From chromic acid or am-
monium bi-chromate’ by
heating.

Apple-green Nickel oxide From nickel nitrate by heat-
ing.

Brown Caramel From sugar by strong heat-
ing.

Blue Berlin blue From yellow prussiate of
potash and iron vitriol.

Blue Turnbull’s blue From red prussiate of pot-

ash and iron vitriol.

Black Carbon From sugar and _ sulphuric
acid.

[117]

14 FIELD MUSEUM OF NATURAL HISTORY

The methods of coloring depend upon the absorp-
tion in the pores of the stone of some substance which,
when acted on by another chemical or by heat, will
give the color desired. Inasmuch as the layers of
agate differ considerably in their porosity, there are
corresponding variations in the amount of color they
will absorb. This gives pleasing variety to the color
effects. The agate colorists call layers which have
great porosity and hence absorptive capacity, “soft,”
while those so compact that they take little or no color
are called “hard.”

For successful coloring, the stone must first be
freed from any substances which would prevent the
entrance of coloring matter into the pores. Thus, all
oils or fats must be removed, as well as iron or other
oxides of an undesirable color. Soaking in caustic
soda solution will remove the fatty substances and
treatment with nitric or hydro-chloric acids undesir-
able iron compounds. For the latter process the stone,
according to Dreher, should be placed in warm acid
for two or three days, and the acid be finally brought
to boiling. After cooling and washing, the operation
should be repeated several times until the pores of the
agate are thoroughly cleaned.

For coloring red, a solution of iron nitrate is used.
This is generally prepared, according to Dreher, by
adding to about half a pound of iron nails, about four
times their weight of concentrated nitric acid. A
more or less slimy mass which is produced is allowed
to settle and the clear liquid poured off, this procedure
being repeated several times until the liquid has be-
come perfectly clear. The stones or sections desired
to be colored are immersed in this liquid at a luke-
warm temperature and allowed to remain for a time
determined by their thickness. Stones 3 millimeters
thick, it is said, should remain 2 to 3 weeks, those 10

[118 ]

AGATE—PHYSICAL PROPERTIES AND ORIGIN 15

millimeters thick, 3 to 4 weeks. Stones thicker than
this can rarely be colored throughout. For the best
results repetition of the treatment is recommended,
the stone being dried after the first bath and then re-
immersed. The agate is now saturated with iron
nitrate and this must be changed to iron oxide by
strong heating. First the stone is dried at a gentle
heat, the time required being from two to ten days,
according to the thickness of the stone. Then, with-
out being allowed to cool, it is put in a closed crucible
on a warm hearth and heated until the hearth be-
comes red hot. It is then allowed to cool very slowly,
care being necessary both in heating and cooling, that
no sudden change of temperature will occur which
would fracture the stone.

For coloring green, as much chromic acid or potas-
sium bi-chromate as possible is dissolved in a quart of
water. The stone desired to be colored is placed in
this bath and if thin, allowed to remain from one to
two weeks, according to the degree of absorption.
Stones one-half inch in thickness often must remain
two months before they absorb sufficient liquid. When
this treatment is finished the stone is placed in a
closed, flat vessel containing lumps of ammonium car-
bonate. It is then allowed to remain exposed to the
fumes of this volatile substance for about two weeks.
It is then dried and gradually and strongly heated
until the desired color is obtained.

For coloring black, about 18 ounces of sugar are
dissolved in a quart of water and the stone allowed
to remain in this solution for from 2 to 3 weeks, ac-
cording to its absorptive capacity. Water must be
added from time to time during the immersion of the
stone in order to replace that lost by evaporation.
The stone is then transferred to a vessel containing
concentrated sulphuric acid and then slowly warmed

{119 ]

16 FIELD MUSEUM OF NATURAL HISTORY

for about an hour. The acid is then brought to boil-
ing for from 15 to 20 minutes or, in some cases, 1 to
2 hours. This latter operation must be carried on with
considerable care, owing to the poisonous nature of
fumes given off by the acid and the explosive action
which occurs if water comes in contact with it. If
one wishes to avoid boiling the acid, the desired effect
can be obtained by allowing the stone to remain in
warm acid for an hour, then cooling and warming it
again for an equal length of time. Owing to the
strong affinity which sulphuric acid has for water, the
acid remaining in the stone will generally cause it to
become moist after it has been removed from the acid.
Drying the stone 1 or 2 days or immersing it for 5 or
6 hours in cold water and then drying it at a moder-
ate temperature will remove this tendency to “‘sweat.”

For coloring blue, a solution is made of 9 ounces of
yellow prussiate of potash (potassium ferro-cyanide)
in a quart of water. In this lukewarm solution the
stone to be colored is left for from one to two weeks,
according to its absorptivity. After being well washed,
the stone is then put into a solution of iron vitriol
(ferrous sulphate) made by adding to a quart of water
as much of the iron vitriol as will dissolve. Left in
this for 8 to 10 days the stone is then removed, well
washed and dried slowly. If a satisfactory color has
not been obtained, the stone can be returned to the
vitriol bath until the desired shade is reached. A
dark blue is produced by a few drops of sulphuric
and a few of nitric acid added to the iron vitriol solu-
tion, or red prussiate of potash (potassium ferricya-
nide) can be used instead of the yellow prussiate of
potash for the first solution. The blue coloring is
much used to imitate lapis lazuli, the so-called German
or Swiss lapis being artificially colored chalcedony or
agate.

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AGATE—PHYSICAL PROPERTIES AND ORIGIN 17

The methods above described will indicate the
principal ones used in coloring agates. By modifications
of these methods other colors can be obtained. Ani-
line dyes can be used, but they are likely to fade in
a short time. An illustration of a number of colors
artificially given to a single section of agate is shown
in Plate VII.

The coloring of agate, like the cutting of agate, is
carried on chiefly in Germany. In the localities de-
voted to this industry it is said to be to a considerable
extent a household occupation, the processes often
being carried on in home kitchens.

CUTTING AND POLISHING OF AGATES

The industry of cutting and polishing of agates is
now carried on chiefly in the vicinity of Idar and
Oberstein, two towns located on the Idar and Nahe
rivers in southwestern Germany. Agates were form-
erly abundant in this region and the art of cutting
and polishing them was developed to such an extent
that when the local supply of agates was exhausted
they were sent there from other localities.

That activity in this line began at a very early
period we know from accounts of it which were given
as early as the year 1497. Subsequently the industry
declined, owing to the depletion of local supplies of
agate, but the discovery of the Brazilian material re-
vived it with great vigor and nearly all modern agate
cutting, coloring, engraving, etc., is now done in this
region.

In carrying on this work, the rough agates are first
broken with hammer and chisel into shapes approxi-
mating those desired. These pieces are then some-
what further shaped on metal wheels charged with
emery or diamond powder, or they may be ground at

[ 121]

18 FIELD MUSEUM OF NATURAL HISTORY

once on great sandstone wheels. These wheels are
often 5 feet in diameter. They contain grooves of dif-
ferent shapes which fit the various forms of agates.
Grinding of the agates to desired shapes is performed |
by workmen who lie prone upon a sort of hollow bench
and, bracing their feet against cleats nailed to the floor,
force the agates with the pressure of their whole bodies
against swiftly revolving grindstones (Plate VIII).
Many of the grindstones are wide enough so that
two workmen can use the same one at one time,
one on either side. The agates usually emit a bright,
phosphorescent light in the process of grinding. The
stones are kept constantly wet with a stream of wa-
ter. Both for this reason and for the water power
needed, the mills in which this work was done were
formerly all located on the banks of streams. At the
present time, however, steam and electrical power and
other modern methods are employed. Vases, bowls
and such objects are hollowed out by special grind-
stones, as much advantage as possible being taken of
the natural contours of the agates. After being ground
to the desired shapes, the articles are polished, this
work being done on wooden wheels to which suitable
polishing powders are applied. This work can be done
by women and children. Owing to its hardness and
toughness agate takes a high and durable polish. Be-
cause of its hardness, toughness and capacity for high
polish, as well as its pleasing patterns and colors,
agate has a number of uses in which ornament is com-
bined with utility. Thus it is made into pen holders,
handles for dental and surgical instruments, umbrella
handles, match boxes and toilet cases. Agate bearings
are of the highest utility for chemical and other bal-
ances and no chemical laboratory is complete without
one or more agate mortars. For ornamental purposes
agate serves for cameos and other stones for breast-

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pins, for hair-pins, ear-rings, watch charms, sleeve
buttons, necklaces, bracelets and rings, especially seal
rings (Plate XI).

It is much prized by many semi-civilized peoples,
especially those of Africa, for ornamental purposes,
and the late Dean C. Worcester once told the writer
that it was one of the most desired objects of barter
in demand among the Filipino peoples.

The engraving of agate, especially to produce cam-
eos and intaglios, is an art which has come down to
us from early times and was principally cultivated by
the Greeks and the Romans. In addition to the artis-
tic excellence of the engravings, many of the early
works show great skill in using the different color-
ings of the agate for decorating the figures. Ex-
amples of such a use of agate are shown in the cameos
of Plate XII.

Agate was long used as the birthstone for June,
but it is now largely superseded in that month by the
pearl. The verse which accompanied the use of agate
was :—

Who comes with summer to this earth,
And owes to June her hour of birth,

With ring of agate on her hand

Can health, wealth and long life command.

In Hall 34 on the second floor of the Museum in a
case near the east entrance, varieties of agate and
their natural and artificial colorings are illustrated by
specimens. Other specimens are shown in the same
hall in their systematic order in the mineral collection,
and in Higinbotham Hall some of the choicer speci-
mens used especially for jewelry may be seen.

OLIVER C. FARRINGTON.

[ 123 J

Agate—Archaeology and Folk-lore

The Sumerians, the earliest inhabitants of Meso-
potamia, were the first nation in history, as far as we
know at present, that recognized the ornamental value
of semiprecious stones and that understood and prac-
tised the art of stone-cutting for the purpose of mak-
ing cylinder seals, signet-rings, beads, and other arti-
cles of jewelry. In the excavations undertaken by
Field Museum at Kish in cooperation with Oxford
University under the auspices of Captain Marshall
Field, great quantities of beads of various substances
and forms have been brought to light. These beads
were worn by both sexes, and the materials commonly
used for their manufacture were agate, carnelian, and
lapis lazuli, which occur in almost every necklace. It
appears from their relative number that carnelian and
agate beads were more popular than those of lapis
lazuli. Many are of oblong, cylindrical shape, up to
two and two and a half inches long with perforations
firmly and evenly drilled. Many examples of such
beads may be viewed in the exhibits of Kish antiquities
in Stanley Field Hall (Cases 6 and 20). In Plate XIII
one of the finest necklaces from Kish is reproduced.
It consists of agate and lapis-lazuli beads alternating,
and also contains beads of gold foil made of the same
shape as those of agate. Perrot and Chipiez figure
a cylinder of veined agate on which are portrayed
winged quadrupeds seizing and devouring gazelles.
It was found by De Sarzec at Tello, and is now in the
Louvre of Paris. The source of the agates and car-
nelians used by the Sumerians has not yet been traced.

Aside from beads, the Sumerians used agate also
for making ceremonial axe-heads. One of these, with
a three-line inscription, is in the American Museum

[ 124 ]

LEAFLET 8. PLATE XI.

MAKING AGATE BEADS.
IDAR, GERMANY.

AGATE—ARCHAEOLOGY AND FOLK-LORE 7A |

of Natural History, New York, and is dated by J. D.
Prince between 3000 and 2300 B.c., probably nearer
the former than the latter date. It is illustrated and
described in Journal of the American Oriental Society,
XXVI, 1905 (pp. 93-97), also in Bulletin of the Ameri-
can Museum of Natural History, XXI (pp. 37-47).
Another Babylonian axe-head of agate, inscribed with
characters of an early form, is in the Metropolitan
Museum of Art, New York.

Agate is first mentioned in literature by Theo-
phrastus (372-287 B.c.) in his small treatise On
Stones. He briefly refers to it as a beautiful stone
which is sold at a high price, and he derives its name
from the river Achates in Sicily, where such stones are
said to have been found for the first time. This ety-
mology is repeated by Pliny, and has been generally
accepted by the ancients. A derivation of the word
from the Semitic has been attempted recently, but is
not convincing.

Pliny, in his Natural History, discusses agate to
some extent, but gives no description of it. He writes
that ‘““Achates is a stone which was formerly held in
high esteem, but is not so now; it was first found in
Sicily, near a river of that name, but has since been
discovered in numerous other localities.”” We may as-
sume that because it was found in numerous localities,
it had lost its former appreciation. Besides Sicily,
Pliny gives Crete, India, Phrygia, Egypt, Cyprus, the
Oeta Mountains, Mount Parnassus, Lesbos, Messenia,
Rhodus, and Persia as places where agate occurred. A
number of varieties are named by him; such names as
laspachates (‘‘jasper-like agate’), smaragdachates
(“emerald agate”), haemachates (“blood agate”), and
leucachates (“white agate’) apparently refer to color
varieties, while dendrachates (“tree agate’) alludes
to the designs in the stone and may correspond to our

[ 125 ]

22 FIELD MUSEUM OF NATURAL HISTORY

moss agate. Corolloachates (“coralline agate’) was
spotted all over, like sapphirus, with drops of gold, and
was commonly found in Crete, where it was also known
as “sacred agate.” It was regarded as capable of heal-
ing wounds inflicted by spiders and scorpions, a prop-
erty which Pliny says might really belong to the stones
of Sicily, as scorpions in that island lose their venom.
The agates found in Phrygia have no green bands, and
those of Thebes in Egypt lack red and white veins.
The Egyptian agate was reputed as an antidote to the
poison of the scorpion, and the stones of Cyprus were
credited with the same property. By some people the
highest value was set upon those stones which present
a transparency like that of glass.

Pliny, further, relates a number of superstitious
notions entertained by the Magi of Persia with refer-
ence to agates. Stones covered with spots like a lion’s
skin were believed to be an efficient protection against
scorpions. In Persia, agates were used, by a process of
fumigation, for stopping storms and hurricanes, as
well as the course of rivers; if they were thrown into a
boiling cauldron and turned the water cold, this prop-
erty was regarded as a proof of their efficacy. A simi-
lar notion, it will be seen below, turns up in China. To
be really efficacious, Pliny adds, the stones must be
fastened with hair from a lion’s mane; hyena’s hair is
rejected in this case, as it is apt to arouse discord in
families. An agate of one color renders the athletes
invincible, the Magi argue, on the ground that if
thrown into a jar filled with oil together with pig-
ments and boiled for two hours, it will impart a uni-
form color of vermilion to all the pigments.

In this case, it was not the agate which in the
opinion of the Magi received new colors, but it was the
coloring matters which through the agency of agate
changed all their colors into one—vermilion. And since

[ 126 ]

AGATE—ARCHAEOLOGY AND FOLK-LORE 23

vermilion was the color proclaiming victory, and agate
had the effect of producing this color in other pigments
of a different nature, the Magi reasoned that an agate
carried by an athlete would lead him to victory. The
question here is not of a technical process, but is
merely one of a purely imaginary, magical supersti-
tion. The doctrines of the Magi are frequently quoted
by Pliny, but as a rule with disapproval.

Another passage in Pliny’s Natural History has
been interpreted by some writers as referring to the
artificial coloring of agates. In fact, however, the
question here is neither of agates nor of artificial col-
oring. Pliny in this case speaks not of achates, but of
cochlides, a word derived from cochlea (‘“snail’’),
which may refer to shells or, according to others, to
petrified shells, or to stones of snail-like shape. Pliny
informs us that cochlides are now very common, being
rather artificial than natural productions, which were
found in Arabia in large masses. These, it is said, are
boiled in honey for seven days and nights uninter-
ruptedly. By this process all earthy and faulty par-
ticles are removed; and thus cleaned, the mass is
adorned by the ingenuity of artists with variegated
veins and spots, and cut into shapes to suit the taste
of purchasers. These articles were formerly made of
so large a size that they were used in the East as
frontals and pendants for the trappings of the horses
of kings.

Pliny, accordingly, speaks merely of purifying a
certain substance of unknown character in honey, but
says nothing about new colors being brought out in it
by means of a chemical process. On the contrary, he
states expressly that veins and spots were added by
the hands of artists. Noggerath, a German scholar,
who was familiar with the artificial coloring of agates
as practised in Idar and Oberstein, has simply inter-

[127]

24 FIELD MUSEUM OF NATURAL HISTORY

preted this process into the above passage of Pliny,
and this speculative hypothesis has been adopted by
many others without reason. There is no evidence
whatever to the effect that the method of coloring
agates artificially was known to the ancients, and the
fact remains that no such agate of classical antiquity
has ever been found.

The Physiologus, a very popular Greek natural
history, which originated at Alexandria in the second
century A.D. and was subsequently translated into all
European languages, contains a story about the agate
and the pearl, which does not occur elsewhere. It is
said that the divers avail themselves of an agate in
searching for pearls. They fasten a piece of agate to
a rope which is let down into the sea. The agate turns
into the direction of where a pearl is hidden, and re-
mains there steadfast, so that they find the pearl by
diving alongside the rope.

Pliny mentions a valuable agate in the possession
of Pyrrhus, the king who was so long at war with the
Romans. On this agate were to be seen the Nine Muses
and Apollo holding a lyre, not as a work of art, but as
the spontaneous produce of nature, the veins in the
stone being so arranged that each of the. Muses had her
own peculiar attribute. We must confess that either it
must have required a high flight of imagination to
recognize these pictures in the veins of this agate, or
that nature had been considerably aided by art.

It is not stated by Pliny or other ancient writers
that agate was cut into gems, but a number of cut
gems of agate have come down to us, and are preserved
in museums or private collections. They go back as
far as the Aegaean or Mycenaean age, agate gems with
mythological subjects having been discovered at
Vaphio. A few cameos of agate and carnelian are on
view in Case 2 (upper left section) of the Gem Room

[ 128 ]

AGATE—ARCHAEOLOGY AND FOLK-LORE 25

(H. N. Higinbotham Hall). Aside from cut gems,
agate was wrought into beads, scarabs, rings, and
figures.

Ointment bottles, cups and bowls were also occa-
sionally made of agate, but few of these have survived.
The best known example is a precious agate bowl pre-
served in Vienna and measuring 2814 inches in di-
ameter. It was brought to Europe by the crusaders
after the conquest of Constantinople. Another famous
agate vessel in existence, presumably made at the time
of Nero, is a two-handled cup holding over a pint and
covered with Bacchanalian subjects. It was presented
by Charles the Bald in the ninth century to the abbey
of St. Denis, and was used to hold the wine at the coro-
nation of the kings of France. In the Treasury of
Vienna there is an agate bowl with a diameter of 30
inches, which is traditionally believed to have been
made about A.D. 1204.

The Persians, Armenians, and Arabs, like all
Oriental nations, do not clearly discriminate between
agate, carnelian, chalcedony, and related stones. The
most esteemed kind is called yamani (“originating
from Yemen’’), as it is chiefly found in Yemen, but,
according to Arabic authors, also came from India and
Maghreb (northwestern Africa). The stone was
chiefly utilized for finger and signet rings in which
the wearer’s name was engraved. A verse from the
Koran or also a magical figure was sometimes carved
in such an agate which then served as a talisman. It
was believed that those wearing a yamani ring were
guarded against the danger of being killed by a col-
lapsing wall or house.

From ancient times India has been celebrated for
the beauty of its agates. Pliny narrates that the agates
of India possessed great and marvelous properties, as
they present the appearance of rivers, woods, beasts of

[ 129]

26 FIELD MusEUM OF NATURAL HISTORY

burden, and forms even like ivy and the trappings of
horses,—alluding to undulated and moss agates. The
druggists of his time, according to Pliny, used these
as stones for grinding drugs, and the very sight of
them was regarded as beneficial for the eyes. Held in
the mouth, they were believed to allay thirst.

In the sixteenth century Limodra in Guzerat was
the principal seat of the agate industry, the mines
being situated four miles from the town. This locality
was visited early in the sixteenth century by Duarte
Barbosa, a Portuguese traveller, who reports, “Here
is found an agate (alaquequa) rock, which is a white,
milky, or red stone, which is made much redder in the
fire. They extract it in large pieces, and there are cun-
ning craftsmen here who shape it, bore it and make it
up in divers fashions; that is to say, long, eight-sided,
round, and olive-leaf shapes, also rings, knobs for hilts
of short swords and daggers, and other ways. The
dealers come hither from Cambaya to buy them, and
they sell them on the coast of the Red Sea, whence they
pass to our lands by way of Cairo and Alexandria.”

Barbosa found also that a great amount of work
was done at Cambay in coral, agate, and other stones.
In the beginning of the seventeenth century the head-
quarters of the agate industry appear to have been
transferred from Limodra to Cambay, in the Bombay
Presidency. Henceforth only the preliminary opera-
tions of sorting the stones and exposing them to fire
to develop their color were performed at Limodra, and
this is the case even now. They are then taken to Cam-
bay to be cut, polished, and worked up.

The Portuguese word alaquequa or alaqueca, also
laqueca, is derived from Arabic al’ aqiq, and refers to
the red carnelians exported from India. The Portu-
guese settled in India called olhos de gato (“cat’s
eyes’) what is known as Indian eye-stone or eye-

[ 130 ]

LEAFLET 8. PLATE XIil.

CAMEOS MADE FROM AGATE (Above).
AGATE CHARMS AS SOLD TO THE NATIVES OF SENEGAL (Below).

AGATE—ARCHAEOLOGY AND FOLK-LORE 27

agate,—small pieces of agate cut en cabochon with a
flattish, circular, or oval back to show the “eye” or
“eyes.” Nicolo Conti, a Venetian, who travelled in
India during the first part of the fifteenth century,
writes that some regions of India have no money, but
instead use for exchange stones which we call cat’s-
eyes.

As is evident from Barbosa’s account, the art of
coloring agates artificially was partially understood in
India. At the present time the stones collected near the
village of Rotanpur near Cambay are classified into
two sorts,—those that should be baked and those that
should not be baked. The object of baking the stones
is to bring out their colors. After exposure to the sun
or by being baked in a cow-dung fire, light browns be-
come white, and dark browns deepen into chestnut. Of
yellows, straw colors become rosy, and orange is in-
tensified into red; other shades of yellow become pink.
Pebbles with cloudy shades turn into brightly veined
stones in red and white. The deeper and the more uni-
form the color, the greater the value. Again, the larger
and thicker the stone, the more is it valued. White
carnelians, when large, thick, even-colored, and free
from flaws, are precious; yellow and variegated stones
are worth little.

Barbosa also mentions at Limodra, or as he calls
the town Limadura, “much chalcedony, which they
call babagore; they make beads with it and other
things which they wear about them.” This is the white
agate of Cambay, called in Anglo-Indian babagooree,
from Hindustani babaghuri. It is so called from the
patron saint or martyr of the district in which the
mines are located, under whose special protection the
miners place themselves before descending into the
shafts. According to tradition, he was a prince of the
great Ghori dynasty, who was killed in a battle in that

[ 131 ]

28 FIELD MUSEUM OF NATURAL HISTORY

region; but this prince is not known from historical
records. By command of Akbar, the Moghul emperor,
grain weights of babaghuri were made to be used in
weighing. All the weights used at court for weighing
jewels were made of transparent white agate.

Agates are much used in India for ornamental
purposes, being made into brooches, rings, seals, cups,
and other trinkets. A considerable trade is still car-
ried on in the raw material which is obtained from the
amygdaloidal flows of the Deccan trap, chiefly from
the State of Rajpipla, where the main source is a con-
glomerate near the village of Ratanpur. Here the right
to collect the stones is leased for a period of five years
at an annual rental. Aside from Cambay, which is the
most important place for cutting agate, this industry
is also carried on at Jabbalpur (or Jubbulpore) and a
few other places within range of the Deccan trap.
Much of the agate sold in Europe is exported from
Cambay, and large quantities are also shipped to
China.

The French traveller and gem-merchant, Jean
Baptiste Tavernier (1605-89), mentions the beautiful
agates cut at Cambay into cups, knife-handles, beads,
and other objects.

Moss agates were formerly known also as tree-
stones (French agates arborisées). John Fryer, who
travelled in India and Persia from 1672 to 1681, de-
scribes the precious stones found in India in his time,
among these tree-stones with the lively representation
or form of a tree thereon.

It was a wide-spread belief among the Moham-
medans of India that agate had the power of stopping
the flow of blood, presumably because of its blood-red
color. The white carnelian was regarded as a ‘“milk-
stone,” and was beneficial to women in increasing their
supply of milk.

[ 132]

AGATE—ARCHAEOLOGY AND FOLK-LORE 29

It is curious that agate is not referred to in ancient
Sanskrit literature, either in medical texts or in mine-
ralogical treatises. On the other hand, great quanti-
ties of agate objects have been discovered on very
ancient archaeological sites of southern India, not only
in the shape of beads, but also in the form of cores,
flakes, scrapers, and strike-a-lights; numerous color
varieties like white, gray, red and white, brown and
gray, banded gray, deep red, dull red, orange-red, etc.,
are represented among these antiquities. It may hence
be inferred that the ancient aboriginal inhabitants of
India were well acquainted with the stone and utilized
it for every-day implements in times anterior to the
Aryan conquest and that the Aryan invaders learned
its use and adopted it from the aborigines.

Agate is appreciated by the Tibetans, and is used
to some extent, though not so largely as turquois, coral,
and amber, their favorite jewels. It is partially im-
ported from India, partially from China, and some is
found in the country itself. Large pieces of red agate
attached to cloth are worn by the Panaka women in
the Kukunor region in their hair which is plaited in
numerous small braids falling over their shoulders.
Agate is frequently used by the Tibetans in finger-
rings (examples in Case 61, West Gallery).

Ancient agate beads, rings, and seals were dis-
covered by Sir Aurel Stein at Khotan and other locali-
ties of Chinese Turkestan; also an intaglio of agate
with the figure of a lion.

The ancient Chinese herbalists and Taoist doctors,
who were chiefly interested in the healing properties
of organic and inorganic substances, classified agate as
a species of its own. Under this term, which is ma-nao
in their language, they included also carnelian. Their
definition of ma-nao is formulated to the effect that it
is neither a common stone nor jade, but that it holds

[ 183 ]

30 FIELD MuSEUM OF NATURAL HISTORY

a rank inferior, but next to their highly prized jade.
Agate, accordingly, was appreciated, though not the
equal of jade and not like the latter a sacred substance.
It was recognized as a hard stone, being capable of
resisting cutting instruments. Red, white, and black
varieties were distinguished. Those which after carv-
ing and polishing offered pictures of. men, animals,
birds, or objects were most highly esteemed. In
southern China a kind of agate of a pure red and with-
out veins was found; it was made into cups and vases.
A dark green variety was obtained in the northwestern
parts of the country. Moss agate is designated
“eypress-branch agate,” also ‘“nettle-hemp agate’;
undulated agate, “cloud agate.” Other terms like
“brocade-red agate, silk-thread agate, rice-water
agate” refer merely to color varieties. “Lampwick
agate” is a variety with white veins. “Dark-like-gall
agate” is what we call bloodstone. “Bamboo-leaf
agate” came from Yi-chou in Shan-tung Province, and
was used for inlaying in screens and tables; as implied
by the name, it displays designs like bamboo leaves.
The same locality produced another kind termed “jade
agate.”

Chinese authors speak of a kind of agate that is
brilliant white of color if looked at straight, but that
appears like coagulated blood if looked at from the
side. It was called “double foetus agate” (kia t‘ai ma-
nao). ‘“Purple-cloud agate” was found at Ho-chou in
An-hui Province.

The ancient Chinese conceived the origin of sev-
eral stones and salts as marvelous transformations
from other substances; thus, white rock-crystal was
believed to be thousand years old water changed into
ice. By a similar process of naive reasoning agate was
interpreted as a transformation of the blood of the
manes or departed spirits, also of malignant devils.

[ 134]

LEAFLET 8, PLATE XIll.
baad
\

NECKLACE OF AGATE, LAPIS LAZULI AND GOLD.

About 3000 B. C. From Excavations at Kish by Field Museum-Oxford University
Joint Expedition (Capt. Marshall Field Fund).

AGATE—ARCHAEOLOGY AND FOLK-LORE 31

Another theory was based on the name for agate,
ma-nao, which means literally “horse’s-brain.” In
writing the two characters, each is usually preceded by
the classifier “jewel” or “precious stone.” The signifi-
cance “horse’s brain’ is regarded by most Chinese
authors as the origin of the word, and may have been
elicited by a certain outward resemblance of the veins
and striation in agate with the brain of a horse. Hence
a popular notion arose that agate beads were spit out
of the mouths of horses.

For the purpose of testing agate the following
recipe is given: “Rub it with a piece of wood; if it
does not become heated, it is genuine; if it will be
heated, it is not genuine.” This test is based on the
notion that the nature of agate is cold and that its
coldness is unchangeable. The Chinese formula is
practically identical with what Pliny ascribes to Per-
sia: there the efficacy of an agate was determined by
throwing it into a cauldron of boiling water and turn-
ing the water cold. It may be that the Chinese derived
this idea from Persia.

In the first centuries of our era the Chinese be-
came acquainted with the fact that agate and many
other valuable stones were abundant in the Near East.
As numerous articles were then traded from the Hel-
lenistic Orient to India and China, while Chinese silk
found its way to the West, it is very probable that
agate was included among the export products of
western Asia.

It is even possible that agate first became known
to the ancient Chinese as an importation from abroad,
for it is not mentioned in the literature of pre-
Christian times, and the earlier authors inform us that
it came from western countries, from the countries in
the south-west, or from the western and southern bar-
barians. In one source it is even stated that it was a

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32 FIELD MUSEUM OF NATURAL HISTORY

product of the country of the Yiie-chi, known to us as
the Indo-Scythians. A tribute of agate was sent from
Samarkand to the Chinese Court in the beginning of
the eighth century. It is specifically asserted that
agate was imported into China by the Arabs, but this
product in all probability was carnelian, as it is de-
scribed as “standard red in color without flaw.” It
was the raw material which was imported and which
was wrought into objects by the Chinese. Subse-
quently, however, agate was discovered by them in
many localities of their country, especially near Ning-
hia, Kwa-chou, and Sha-chou in Kan-su Province and
in the outlying deserts, also in some mountains of
northern Shan-si, Chi-li, and Shan-tung.

Toward the end of the Ming dynasty, in the first
part of the seventeenth century, as we learn from a
Chinese cyclopaedia completed in 1632, agate was im-
ported into China from Europe; this became known
as “foreign agate.” That of red color was most highly
appreciated; in its interior it displayed branches of
cypresses and veins of various colors, as fine as silk
threads; a variety with white veins was regarded as
superior. Soon afterwards the same stone was dis-
covered in Ytin-nan, and was termed “native agate.”
The Ai-lao Mountains in the prefecture of Yung-
ch‘ang of that province enjoy a special reputation for
their agates. Agate was also imported into China from
Japan in three varieties—red, black, and white. As
stated above, rough agates are exported from India to
China in considerable quantities, particularly to Canton.

Small flat disks of red agate, usually covered under
the surface with fine white lines of clayish origin, have
been found in graves of the Han period (206 B.C.-A.D.
220). There are several early records of wine-vessels
of agate having been discovered in tombs. Horse’s-
bits of agate are also mentioned. Large agate beads of

[ 136 ]

AGATE—ARCHAEOLOGY AND FOLK-LORE 83

circular and cylindrical shapes, rings and bangles, as
well as small disks of translucent moss agate are
traceable in graves of the T‘ang (A.D. 618-906) and
later periods. An ancient necklace or rosary found in
a grave of Shen-si Province and shown in Case 38,
East Gallery, consists of beads carved from agate,
lapis lazuli, jade, and jujube-stones.

In A.D. 662 a tree three feet high made of agate
in the shape of a lamp was sent by the country To-
khara as a gift to the Chinese emperor. The branches
of this agate tree were presumably fashioned in such
a manner that they could hold an oil-lamp or candle.
In more recent times jade trees were made by the
Chinese as wedding gifts. In many of these leaves and
flowers are carved from jade, but agate and carnelian
are much used for the petals of the blossoms, as may
be seen in a good example of the Blackstone Chinese
Collection (Case 1). A paper-weight of white and red
agate in which eight lizard-shaped dragons are carved
is on view in the same case.

Formerly agate was also wrought in China into
hair-pins, fish-hooks, and chessmen; and large slabs
were used for desk-screens and table tops. The art-
loving emperors of the Sung dynasty (A.D. 960-1278)
had a high appreciation of agate. In A.D. 1115 some
large agate blocks were found and transported into
the imperial atelier, where they were wrought into
precious objects like vases and ornamental plaques for
girdles which were preserved in the imperial treasury
for more than a century. Finally the colors are said
to have faded away, and the stones assumed the color
of white bone, whereupon the objects were discarded
and disposed of to the people. In A.D. 1272 the Mongol
emperors established in their capital Ta-tu and other
places an “Agate Bureau” in charge of a director who
supervised five hundred workmen.

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34 FIELD MUSEUM OF NATURAL HISTORY

In the fourteenth century there were made finger-
rings inlaid with a piece of agate in which were en-
graved the twelve horary characters corresponding to
the twelve signs of the zodiac. A contemporary author
describes the work of engraving as fine as hair and
conveying the impression as though it were not an arti-
fact of man; it was therefore styled “devil’s work
stone” or “stone of the devil’s country.”

Powdered agate is said to have been used together
with copper oxide and other ingredients in the produc-
tion of a red glaze on porcelains.

The great force of the Chinese lapidary is the
carving of snuff-bottles in which he strives at bringing
out the colors of the stone to best advantage, or cuts
the designs in layers so that the different colors stand
out in relief as in antique cameo-work (Plate XIV,
Fig. 3). Agate snuff-bottles are on view in the case
illustrating the use of tobacco in China (south end of
West Gallery). Some of these are reproduced in Leaflet
18 of the Department of Anthropology (Plates VIII
and IX). The sentiment attached to the gift of a snuff-
bottle of moss agate is that it should be a disperser of
melancholy.

During the K‘ien-lung period (1736-95) and some-
what later fine agate carvings were also made to be
worn as pendants in the girdle. Three such ornaments
are illustrated in Plate XIV, Figs. 1-2 and 6. The
pendant in Fig. 1 represents a carp with lotus leaves;
that is, the carp is conceived as swimming in a lotus
pond. That in Fig. 2 shows a bird with a fruit, leaves,
and blossom. That in Fig. 6 is carved into three ju-
jubes (Zizyphus vulgaris) with two small peanuts
(only one is visible in the illustration). The snuff-
bottle in Fig. 3 is of milk-white agate with relief carv-
ings in black, brown, and yellowish layers. These rep-
resent two monkeys, a spotted deer (Cervus manda-

[ 138 ]

EEAFLET-8. PLATE XIV.

5 6

AGATE ORNAMENTS AND SNUFF-BOTTLES, CHINA.
1-2, 6, GIRDLE PENDANTS; 5, RING OF MOSS AGATE.
Capt. Marshall Field Expedition to China, 1923.

3-4, SNUFF-BOTTLES.

From the Collection of Mrs. George T. Smith, Chicago.

AGATE—ARCHAEOLOGY AND FOLK-LORE 35

vinus), and a magpie flying into the open from a pine-
tree. Fig. 4 is a plain agate bottle of various colors,
brown in the upper portion and green in the lower
one. Fig. 5 is a ring of moss agate, 134, inches in
diameter.

Agate was traded by the Chinese to their neigh-
bors, the Tibetans, Mongols, Manchu, and Japanese,
all of whom have adopted their word ma-nao (in Japa-
nese meno). The Japanese, like the Chinese, manu-
facture agate and carnelian into beads for rosaries,
paper-weights, ink-stones for rubbing the cakes of
ink on, fruits, buttons, seals, tea and wine cups, and
in particular into the small ornaments known as
netsuke.

It is known in Japan that agate becomes more
opaque on being exposed to sunlight or subjected to an
intense heat in a closed jar, but the methods of color-
ing agate artificially, as employed in Europe, were un-
known both in China and Japan.

The agate found in the province of Kaga was re-
garded as very precious. A red variety of it was called
“‘vine-grape stone,” and served for plaques to be inlaid
in girdies in the place of jade. The provinces Mutsu,
Echiu, Suruga, and Kai have the highest reputation
for their agates and the skill of their lapidaries. Agate
was formerly also imported into Japan from China.

Agate, being found in numerous localities of
America, attracted the attention of the aboriginal in-
habitants at an early date. In North America and
Mexico agate was wrought into arrow-heads and spear-
heads. A beautiful agate spear-head, for instance, was
found in one of the Hopewell mounds of Ohio. The
Museum has numerous agate beads recovered from
prehistoric graves of Colombia, South America.

B. LAUFER.

[ 139 ]

Additional information about Agate can be ob-
tained from the following works:

LIESEGANG, RAPHAEL Ep.—Die Achate. Theodor Steinkopf,
Dresden and Leipzig, 1915. 118 pp.

DREHER, O.—Das Farben des Achates.

E. Kessler, Idar, 1918.
20 pp.

BavurerR, Max.—Precious Stones. Translated with additions by

L. J. Spencer. Griffin and Company, Ltd. London,
1904. 627 pp.

KuNz, GEORGE F.—Gems and Precious Stones of North America.
Scientific Publishing Company, New York, 1890. 336 pp.

The Magic of Jewels and Charms. J. B. Lippincott Co.,
Philadelphia. 1915. 422 pp.

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