DEPARTMENT OF THE INTERIOR
UNITED STATES GEOLOGICAL SURVEY
GEORGE OTIS SMITH, Dikectok
Bulletin 432
SOME ORE DEPOSITS IN MAINE
AND
THE MILAN MINE, NEW HAMPSHIRE
BY
WILLIAM H. EMMONS
QE
-B9
WASHINGTON
GOVERNMENT PRINTING OFFICE
1910
DEPARTMENT OF THE INTERIOR
UNITED STATES GEOLOGICAL SUliVEY
GEORGE OTIS SMITH, Director
Bulletin 432
SOME ORE DEPOSITS IN MAINE
AND
THE MILAN MINE, NEW HAMPSHIRE
WILLIAM H. EMMONS
WASHINGTON
GOVERNMENT PRINTING OFFICE
1910
YiQ •
^^'^
CONTENTS.
Pa?e,
Introduction 7
General statement 7
Acknowledgments 8
Bibliography 8
Geography 10
Mining development 10
Production of metals 11
Geology 11
Sedimentary rocks 11
Ellsworth schist 11
Islesboro formation 12
Battle quartzite 12
Penobscot formation 12
Ames Knob formation 12
Perry formation 13
Igneous rocks 13
Castine formation 13
North Haven greenstone 13
Thorofare andesite 14
Vinalhaven rhyolite 14
Granite 14
Diorite 15
Basic lava flows 15
Basic dikes 15
Ore deposits 15
Classification 15
Deposits older than regional metamorphism 15
Distribution and character ^. 15
Metamorphism 18
Origin 20
Deposits associated with granite intrusions 20
Fissure veins 20
Molybdenite and lead deposits. . .A^»*. i^^ HTl. 21
Deposits associated with diabase and trap 22
Mineralogy 22
Distribution of outcrops 24
Oxidation and secondary enrichment 25
Future of the mines 26
Lead, zinc, and silver 26
Copper 27
3
4 CONTENTS.
Ore deposits — Continued. Page-
Summary of geologic events as related to ore deposits 27
Pre-Cambrian and Cambrian time 28
Silurian time 29
Devonian time 29
Quaternary time - 30
Descriptions of mines 30
Mines of Hancock County 30
General statement 30
Douglas mine 31
Twin Lead mine 32
Blue Hill mine 33
Stewart mine 33
Mammoth mine 34
Owen mine 34
Owen lead prospect 34
Granger mine 35
Weil Freddie mine 35
Tapley mine 35
Eggemoggin mine 36
Deer Isle mine 37
Cape Rozier mine 38
Hercules mine 38
Jones & Dodge mine 38
Emerson mine 39
Sullivan, Waukeag, and Pine Tree mines 39
Gouldsborough mine - - 40
Franklin Extension mine ". ". - - - 41
Copperopolis mine - - "? 41
Catherine Hill molybdenum mine 42
Mines of Washington County 43
General statement - 43
Cherryfield mine 43
Lubec lead mine 44
Denbow Point mine 45
Prospects in Pembroke 46
Cooper mine 47
Mines in Somerset and Oxford counties 48
Robinson mine 48
Mount Glines deposits 49
Milan mine, New Hampshire 50
General statement 50
Geology 52
Minerals of the ore 54
Ore bodies 55
Summary of the genesis 59
Index 61
ILLUSTRATIONS.
Page.
Plate I. A, Photomicrograph of schistose ore from Deer Isle mine; B, Pho-
tomicrograph of thin section of ore from Owen lead prospect 20
II. Geologic map of mineralized area of Blue Hill 30
III. A, Polished surface of schistose ore of Milan mine; B, Photomicro-
graph of molybdenite ore from Catherine Hill 42
Figure 1. Outline map of southern Maine 7
2. Stringer of contorted pyrite in contorted rhyolite near the Tapley
lode 16
3. Quartz-pyrite veinlet leading off from Twin Lead lode 17
4. Plan of part of the 115-foot level, Milan mine 17
5. Ore from Twin Lead mine, Blue Hill 18
6. Thin section of ore from Milan mine 19
7. Thin section of schistose ore from Deer Isle mine 20
8. Ore from Sullivan mine 21
9. Brecciated diabase cut by quartz and sulphides, Pembroke mine. . 22
10. Section along line A-A^, Plate II 31
11. Section along line B-B^ Plate II 31
12. Cross section of the Sullivan mine 39
13. Sketch showing position of principal veins in Lubec lead mine 44
14. Small vein in Lubec lead mine 45
15. Sketch showing position of pits of Eastern Exploration Company at
Pembroke ■- 46
16. Plan and cross section of Robinson mine, near Concord 48
17. Vertical cross section of wall at open cut, Robinson mine, near Con-
cord 49
18. Plan of ore treatment at Milan mine 51
19. Geologic east- west cross section through West Milan, N. H., north of
Milan copper mine 54
20. Pyrite cut by quartz, Milan mine 54
21. Section of vein at east end of 115-foot level, Milan mine 55
22. Cross section of ore bodies, Milan mine 56
23. Plan of 115-foot level, Milan mine 57
5
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SOME ORE DEPOSITS IN MAINE AND THE MILAN
MINE, NEW HAMPSHIRE.
By William H. Emmons.
INTRODUCTION.
GENERAL STATEMENT.
Metal mining does not rank as an important industry in Maine,
for, aside from iron ore, the deposits of whicli were once worked with
some vigor, the metallic production of the State has been small. It
contains, however, deposits of nearly all the commoner metals and,
Figure 1. — Outline map of southern Maine.
owing to the complex relations of the rocks and the eventful geologic
history of the region, the number of typos is not surpassed in many
areas of equal size in regions of greater mineralization and larger
ore deposits.
8 SOME OKE DEPOSITS IN MAINE AND NEW HAMPSHIKE.
The economic reconnaissance described in the present paper was
made during six weeks of the summer of 1909, in which time all of
the most important deposits of the metals other than iron were visited.
Figure 1 shows the positions of the towns and of villages near
which the mines are located. As many of them are in localities where
the areal geology has been worked out in detail and where the struc-
tural relations of the rocks are well understood, the history of the
ore deposits may be stated with confidence. The conditions for
underground work were not good, because nearly all of the mines
were closed down and the shafts partly or entirely filled with water,
but owing to the slight oxidation of the surface, the relations of the
deposits and the character of the ores could be studied in many open
cuts and at the higher levels above ground water.
In connection with this work the Milan mine, in Coos County, N. H.,
was visited. The deposit which is now successfully worked at this
mine is only a few miles west of the Maine boundary and closely re-
sembles some of the deposits in Maine. Its description is included in
this report for the purpose of comparison.
ACKNOWLEDGMENTS.
The writer gratefully acknowledges his indebtedness to George
Otis Smith and E. S. Bastin, whose published papers have supplied
most of the geologic data for this report and who have given the
writer unpublished notes on some of the mines; to Walclemar Lind-
gren, of the United States Geological Survey, for direction and criti-
cism ; to F. C. Robinson, state geologist of Maine ; to Messrs. J. B.
Carper and J. B. Morris, of Portland, for many courtesies; and to
the owners of the mines and prospects, for the free access granted to
their properties.
BIBLIOGRAPHY.
The following list is intended to include the most important pub-
lications on the ore deposits of Maine and their associated rock forma-
tions :
Bartlett, F. L., Mines of Maine, Portland, 1879.
A discussion of the ores, with numerous assays and notes on the organ-
ization and capitalization of various mining companies operating in Maine.
P.A.sriN, Edson S. a pyrrhotitic peridotite from Knox County, Me. — a sulphide
ore of igneous origin : Jour. Geology, vol. 16, 1908, p. 124.
Describes a peridotite in which olivine and cupriferous pyrrhotite are
intimately intergrown in such a manner as to show contemporaneous age.
Eastport folio, (Jeol. Atlas TJ. S. (In preparation.)
Numerous geologic data soon to be published in this folio have been
freely contributed by Mr. Bastin and are incorporated in the present report.
Cakpkr, J. B. The Milan mine, NeAV Hampshire. Eng. and Min. .Jour., vol. 87,
1909, p. .318.
A brief note giving niclal contents of ore shipments from the Milan mine.
IISITRODUCTION. 9
Hess, Frank L. Some molybdenite dejiosits of Maine, TTtah, and California :
Bull. U. S. Geol. Survey No. 340, 1908, p. 231.
Describes tlie molybdenite deposits of Cooper, Catherine Hill, and Paris,
Me., and concludes tbat tlie molybdenite is of pegmatitic origin.
Holmes, Ezekiel, and Hitchcock, C. H. Preliminary report upon the natural
history and geology of the State of Maine, 1861.
This report Includes many valuable geological data, vsith notes on the
occurrence of bog iron ores and magnetic iron ores at various places.
Several occurrences of lead and zinc and other metals are mentioned, and
extracts from a report by N. S. Manross on the Lubec lead mine are
incorporated.
Hitchcock, C. H. Geology of Maine: Second Ann. Rept. Natural History and
Geology of Maine, Geology, 1862, pp. 223-430.
The report includes detailed descriirtions of rock formations and cross
sections showing the geologic structure at many places along the Maine
coast, and gives some running notes on the geology of the northern portions
of the State. A list of mineral occurrences and a catalogue with brief
descriptive notes on Mount Mica minerals is included. Incorporated in the
volume is a report by G. L. Goodale on various occurrences of ore minerals
and on the economic possibilities of the iron ores.
Jackson, Charles T. First report on the geology of the State of Maine, 1837.
Some interesting notes of a geologic reconnaissance, with descriptions
of building stones and various mineral occurrences.
Second report on the geology of the State of Maine, 183S.
Gives some cross sections in the region of Blue Hill, with descriptive notes
on the rocks involved. Describes granite, limestone, and shale quarries
and the deposits of serpentine on Deer Isle. Includes notes on the tech-
nology of iron and of copperas manufacture on Jewel Island, Casco Bay.
Third annual report of the geology of the State of Maine, 1838.
Includes notes of geologic reconnaissance, with a list of rocks, ores, and
minerals from various localities.
Kempton, C. W. Sketch of the new mining district at Sullivan, Me. : Trans.
Am. Inst. Min. Eng., vol. 7, 1878, p. 349.
An account of the geology and ore deposits at Sullivan, with several
geologic cross sections of that I'egion. A paper of historical value, describ-
ing deposits which have not been worked for many years.
McCaskey, H. D. Mineral resources of the United States for 1908, pt. 1,
Metallic products, U. S. Geol. Survey, 1909, pp. 142, 146, 247, 658.
Notes on various metalliferous deposits of Maine.
Smith, George Otis. Quartz veins in Maine and Vermont : Bull. U. S. Geol.
Survey No. 225, 1904, p. 81.
Describes quartz veins at Mount Glines, Oxford County, and a pegmatite
near Pittston, Kennebec County, which has been erroneously regarded as a
gold ore.
A molybdenite deposit of eastern Maine : Bull. U. S. Geol. Survey
No. 260, 1905, p. 197.
Graphite in Maine : Bull. U. S. Geol. Survey No. 285, 1906, p. 480.
Describes occurrences of graphite near Madrid, Franklin County, and
near Yarmouth, Cumberland County.
Smith, George Otis, Bastin, Edson S., and Brown, Charles W. Penobscot
Bay folio (No. 149), Geol. Atlas U. S., U. S. Geol. Survey, 1907.
This folio furnishes the most comprehensive geologic data for Maine
now available, and a considerable portion of the geologic descriptions of
the present report are taken from it.
10 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE,
Smith, George Otis, and David White. The geology of the Perry Basin : Prof.
Paper U. S. Geol. Survey No. 35, 1905.
This paper is the result of an investigation of the rocks of the Perry
Basin to ascertain whether there is a probability of finding coal there. The
rocks of this basin are fossiliferous and are interbedded v\^ith the lavas,
and their study has resulted in disclosing important relationships. The
spherulitic rhyolites, which are devitrified and somewhat deformed by
metamorphism, are interbedded with fossiliferous Silurian strata and are
believed to be the effusive equivalent of the same magma which, solidifying
at greater depth, formed the great granite intrusive that extends from
Robbinston northward to the vicinity of Calais. The Perry formation,
which rests above the Silurian and is less deformed, is made up of conglom-
erate and sandstone and includes beds of basaltic lavas. Since the Perry
carries Devonian fossils the basic lavas are known to be of that age.
Pebbles of granite are found in the conglomerate but not in the underlying
Silurian rocks.
Smock, John C. Mineral resources U. S. for 1882, p. 687.
A list of " Ores, minerals, and mineral substances of industrial im-
portance " which are mined in Maine.
Stone, George H. The glacial gravels of Maine and their associated deposits :
Mon. U. S. Geol. Survey, vol. 34, 1899.
A comprehensive report on the glacial deposits of Maine. A discussion
of glacial processes and a comparison of the continental glacier with those
of the Rocky Mountains.
GEOGRAPHY.
The State of Maine is for the most part a low plateau, the higher
portions of which are deeply trenched by rivers and creeks. Many
hills and low mountains rise above this plateau, and it is thickly
dotted by lakes and ponds. The coast line is very irregular. Long,
narrow bays with deep water channels extend far inland and since
these are- navigable for small ocean craft transportation facilities are
good and freight rates low.
MINIISTG DEVELOPMENT.
Granite and limestone are quarried in large quantities and have
a wide market. The metalliferous deposits, although they have not
been abandoned, are not now being exploited. Mining was done in
a small way in the early part of the nineteenth century. In the
second report by Charles T. Jackson on the geology of the State,
published in 1838, mention is made of a pyrite mine on Jewel Island,
Casco Bay, where copperas and alum were manufactured. Later the
iron ores of Mount Katahdin- were developed; and for a long term
of years, ending about 1800, these deposits produced from 2,000 to
15,000 tons of iron a year. The Lubec lead mines, which were dis-
covered in the late thirties, were worked with some vigor in the early
sixties.
GEOLOGY. 11
The principal period of development was from 1878 to 1882,
during which time the districts along the coast were having a mining
boom that in all essentials resembled those periods of excitement
notable in the history of many western camps. Mining companies
with ample capitalization were organized to exploit the deposits of
Blue Hill, Sullivan, and near-by districts. Substantial mine build-
ings were erected ; expensive machinery was installed ; and in some
instances mills, concentrators, or smelters were built. At the Doug-
las mine, in Blue Hill, large sums were spent on smelters and roasting
and leaching plants and several hundred tons of copper was recov-
ered. In 1883 the price of copper dropped considerably and the
Douglas and other mines of Blue Hill were closed. The silver mines
at Sullivan were closed soon afterward and have since been idle. The
mines at Lubec and the Robinson mine, at Concord, have been worked
in recent years, and between 1900 and 1907 prospecting was done at
several places, but no large operations have been carried on since
the eighties.
PRODUCTION OP METALS.
The quantity of metals produced in Maine can not be given accu-
rately. The total value of all metals other than iron is conservatively
estimated at $400,000, the larger part of which is copper from the
Blue Hill mines. The silver mines at Sullivan and at Byard Point
probably yielded at least 5,000 ounces. A number of mines have
yielded relatively small quantities of lead and zinc.
GEOLOGY.
The following discussion of the general geology of Maine is taken
almost entirely from published papers of G. O. Smith and E. S. Bastin
(see pp. 8-9), and from verbal statements made by them, and is
intended to include only such data as have a direct bearing on the
genesis and history of the ore bodies.
SEDIMENTARY ROCKS.
Ellsworth schist {pre-G ambrianf) . — The Ellsworth schist is the
oldest rock outcropping in the areas of mineralization, and is the
country rock for many of the ore deposits. Large areas occur in
Hancock County near Blue Hill (see PI. II), and it extends eastward
to Sullivan and beyond. It is composed of highly schistose meta-
morphic rocks which presumably are the changed equivalents of
siliceous shales and argillaceous sandstones. The rock is purple to
greenish gray in color and is finely foliated. At most places meta-
morphism has obliterated all traces of bedding, but on the east shore
of Skilleys River in the Mount Desert quadrangle massive quartz-
ite beds alternate with the more argillaceous layers. Under the micro-
12 SOME ORE DEiPOSITS IN MAINE AND NEW HAMPSHIRE.
scope the chief constituent minerals are seen to be quartz and chlorite.
The chlorite occurs in thin parallel plates and gives the rock its
schistosity. The quartz fragments have been rotated during the
process of metamorphism so that the longer axes lie parallel to the
chlorite leaves. Some biotite, muscovite, epidote, and magnetite are
present in varying quantities. The schist is intruded by the Castine
volcanic rock, by granite, and by diorite and is clearly older than all
of these. Since formations known to be later than the Ellsworth are
very probably Cambrian, the Ellsworth is presumably very early
Cambrian or pre-Cambrian.
Isleshoro formation {^Cambrian?). — Thelslesboro formation, which
occupies a large part of Islesboro, is a series of metamorphosed slates
and limestones at least 300 feet thick. It is everywhere strongly
folded and at many places shows a well-developed slaty cleavage
which intersects the bedding planes at high angles. On Seven Hun-
dred Acre Island the slaty members contain intensely crumpled
quartz veins. The Coombs limestone member forms the top of the
formation and is overlain by the Battie quartzite. In the southern
part of Job Island the limestone is interbedded ^vith dark-green
layers which seem to be volcanic tuffs or muds of the North Haven
greenstone. The slate member likewise contains volcanic material of
the same age and origin. In the metamorphism which has affected the
formation the limestone has completely recrystallized and the shaly
beds have at most places become schists. No fossils have been found
in the formation, but on stratigraphic grounds it is thought to be of
Cambrian age.
Battle quartzite {Cambrian f) .—The Battie quartzite, which con-
sists of massive buff quartzite and quartzite conglomerate several
hundred feet thick, rests directly upon the Coombs limestone member
of the Islesboro formation without any apparent unconformity. It is
well exposed at Mount Battie, a small mountain near Camden. It
is not highly crumpled, as is the slate phase of the Islesboro, because
it was less yielding. It is believed to be of Cambrian age.
Penobscot formation {Cambrian f). — The Penobscot formation,
typically developed along the west shore of Penobscot Bay, is com-
posed of metamorphosed shaly sediments which overlie the Battie
quartzite. A distinct and perfect schistosity is commonly j^resent,
and the formation is at places intensely folded into isoclinals. At
Ducktrap Harbor the slates are intruded by granite, and garnet, anda-
lusite, and other minerals have formed by contact metamorphic proc-
esses. The Penobscot formation is believed to be of Cambrian age.
Am,es Knob formation {Silurian). — The Ames Knob formation,
which is made up of limestones, red shales, and conglomerate, con-
tains Niagara fossils. It has been gently tilted in places, but the
compressed folds and minor crumplings characteristic of the Penob-
GEOLOGY. 13
scot, Islesboro, Castine, and North Haven formations are entirely
absent. Clearly it has been deposited since the time of the regional
metamorphism of the country. The basal member is a conglomerate,
which includes rounded fragments of North Haven greenstone and
of green slate, quartzite, and vein quartz. The upper portion of the
formation contains volcanic material, and in the Penobscot Bay quad-
rangle it grades into the Thorofare andesite. In the Perry Basin
fossiliferous Silurian strata are interbedded with rhyolites.
Perry formation {Devonian). — The Perry formation," which in the
Perry Basin overlies the Silurian rocks, consists of a lower conglom-
erate member, above which are beds of basaltic lava and breccia.
Above the latter is coarse red and brown sandstone with included
conglomerate and lava layers. Above this still is a green amygdaloid
and sandstone. The plant remains show the formation to be of
Devonian age. Except for certain glacial deposits, formed in com-
paratively recent times by the ice sheet which covered the entire State,
no sedimentary beds younger than the Perry are known to occur in
the areas of mineralization.
IGNEOUS ROCKS.
Castine formation {Camhrianf). — The Castine formation, which
is typically developed on the Castine Peninsula, is made up of light-
colored lavas and pyroclastic rocks including rhyolite, dacite, and
andesite. These rocks occur as flow breccias, conglomerates, tuffs,
intrusive sheets, and dikes. The great bulk of them are meta-
morphosed dynamically, and some, which were presumably volcanic
muds, are highly schistose. Some of the tuffs seem to have been rich
in lime carbonate. Chlorite, sericite, biotite, and cordierite have in
places been developed in the Castine by secondary processes. Tremo-
lite, biotite, and other minerals have developed by contact meta-
morphism. A similar association of minerals with sulphides and
abundant garnet is found at the Deer Isle mine. (See p. 37.) The
Castine formation is in a general way contemporaneous with the
Islesboro formation and is believed to be of Cambrian age.
North Haven greenstone {Cambrian ?). — The North Haven green-
stone, which is extensively developed on the island of North Haven
and on neighboring smaller islands, is made up of regionally meta-
morphosed diabase, basic trachyte, and albite-augite syenite, which
occur as tuffs, flows, dikes, and sills. The different varieties, whicli
are at many places indistinguishable, are associated in the most inti-
mate and irregular manner and are believed to be contemporaneous.
At some places these rocks show highly developed schistosity.
Fibrous actinolite, zoisite, calcite, muscovite, biotite, and chloritic
» Smith, G. 0., and White, David, Prof. Paper U. S. Geol. Survey No. 35, 1905, p. 28.
14 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
minerals are developed by regional metamorphism. The North
Haven greenstone is older than the Silurian sediments; and since
the Islesboro formation contains much fragmental material of com-
mon age and origin with the North Haven greenstone, the latter is
believed to be contemporaneous with the Islesboro and nearly con-
temporaneous with the Castine. Both formations are probably
Cambrian.
Thorofare andesite {Silurian). — The Thorofare andesite, which is
extensively developed along the Fox Island Thorofare, includes
massive porphyritic andesite, amygdaloid, tuffs, flow breccias, and
conglomerate. These volcanic rocks, which are not regionally meta-
morphosed, overlie the upper members of the Ames Knob (Silurian)
formation and have about the same attitude. The red shales at the
top of the Ames Knob contain volcanic dust, which probably repre-
sents the earliest Thorofare eruptions.
Vinalhaven rhyolite {Silurian). — The Vinalhaven rhyolite, ex-
posed in the northwestern part of the island of Vinalhaven, is made
up of surface flows. Some are glassy and show flow structure ; some
are taxitic and spherulitic. They overlie the Thorofare andesite,
and at some places fragments of the latter are mixed with the rhyolite
flows, the rhyolite constituting the matrix. They are in the main
younger than the Thorofare, but near the line of contact of the two
formations beds of rhyolite alternate with beds of andesite. It
seems probable that the two kinds of lavas were erupted from sepa-
rate neighboring vents, the volcanic activity beginning with the
eruption of the andesite and ending with that of the rhyolite. The
andesites and rhyolites are of post-Niagara age, probably late Silu-
rian, and older than the granite.
Granite. — Along the Maine coast from Calais to Portland and
beyond granite covers large areas. At most places it is gray or pink
and medium grained. The common constituents are orthoclase,
microcline, albite, biotite, and muscovite. The granite shows no
schistosity such as results from regional metamorphism. It cuts the
Ellsworth, the Castine, and other pre-Silurian formations and sends
off apophyses into them. The intruded rock is frequently recrystal-
lized near the contact, where some andalusite has formed, but no ex-
tensive garnet zones are developed. The granite cuts rocks which are
known to be younger than the Ames Knob formation, and it is there-
fore as late as Silurian. In the Perry Basin no granite pebbles are
found in the Silurian, but late Devonian conglomerates (Perry) con-
tain abundant rounded fragments of the granite. The coast granites
of Maine were therefore intruded in late Silurian or early Devonian
time, and it has been suggested " that they are about contemporaneous
» Smith, G. O., Prof. Paper U. S. Geol. Survey No. 35, 1905, p. 20.
GEOLOGY. 15
Avitli certain of the Silurian rhyolites. The granite apparently was
not rich in metals, although some of the ore deposits appear to be
related to it genetically.
Diorite^ etc. — Diorite, diabase, and gabbro are associated with the
granite and are believed to be somewhat earlier but essentially con-
temporaneous differentiations from the same magma. They are dark
rocks of medium grain and are free from schistosity. At some
places diorite and granite may be seen grading one into the other,
and dikes of either rock may cut the other. The Gouldsborough
lode is a fissure vein in diorite which near by is brecciated and
cemented by medium-grained granite.
Basic lava flows. — In the Perry Basin, near Lubec, in Pembroke,
and at many other places in Washington County there are great
flows of basic lavas, including basalts, diabase, and " trap rock."
In the Perry Basin these are interbedded with sandstone and con-
glomerate carrying late Devonian fossils, showing that at least some
of the flows are of late Devonian age.
Basic dikes. — The granite and the older rocks are cut by dikes of
diabase, basalt, and analcite basalt. Some of these are doubtless
very old, others are believed to be the intrusive equivalents of the
lavas included in the Perry formation, while others still are probably
Mesozoic (Triassic?). A basaltic dike cuts across the Robinson lode
at Concord, Somerset County, and is very clearly later than the ore.
The basalt at the intersection is so fresh that even the olivines shoAv
very little of the characteristic alteration to serpentine along cracks.
ORE DEPOSITS.
CLASSIFICATION OF DEPOSITS.
The principal ore deposits of Maine, not including the iron ores
nor the gem-bearing pegmatites, may be divided into three groups —
(1) deposits formed before the end of the last period of great
regional metamorphism ; (2) deposits associated with the granite in-
trusions; and (3) deposits associated with eruptions of diabase or
trap.
DEPOSITS OLDER THAN REGIONAL. METAMORPHISM.
Distribution and character. — The pre-metamorphic deposits are the
most important. All the known representatives are in Hancock
County, in the hilly country between Penobscot and Blue Hill bays.
They include, stated in order of importance, pyritic copper ores,
garnetiferous zinc ores, and siliceous zinc-lead-silver ores. All are
in the Ellsworth schist and the Castine volcanic rocks — the Twin Lead,
Douglas, Blue Hill, Stewart, Mammoth, Owen Copper, Granger, and
Weil Freddie being in the Ellsworth, and the Tapley, Deer Isle,
16
SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
Cape Rozier, Emerson, and Hercules in the Castine. In all the mines
in which the ore bodies are exposed the sulphides appear disseminated
through the rock, as lenses approximately parallel to the schistosity,
or as deformed breccia zones.
The copper deposits near Blue Hill and Brooksville are the most
important. All of the mines have lain idle for years and their
underground workings are inaccessible, but the character of the ore
and its relations to the structure are shown in a number of deep
open cuts. Except at the Tapley mine, which is in the Castine forma-
tion, the Blue Hill and Brooksville deposits are all in the Ellsworth
schist. This is a siliceous sedimentary rock which has been meta-
morphosed at great depths and under pressure. (See p. 11.) The
minerals of the ore are quartz, chlorite, muscovite, biotite, pyrite,
chalcopyrite, pyrrhotite, magnetite, arsenopyrite, bornite, chalcocite,
and a little zinc blende and galena. Near Blue Hill the deposits
lie approximately parallel to the schistosity, striking from S. 87° E.
to N. 77° E. and dipping
from 45° S. to vertical.
The lodes are from 5 to 20
feet wide and are said to per-
sist along the strike for sev-
eral hundred feet. Their
central portions are as a rule
composed of massive pyrite,
with which some chalcopyrite
and other sulphides are inter-
grown. Some quartz is pres-
ent. Toward the wall thin
slabs of schistose quartz and
chloritic rock are included
in the pyritic ore. These slabs and their constituent minerals lie
nearly parallel to the schistosity of the country rock and the trend of
the deposit. The walls themselves, which are of the same composition
as the slabs, contain stringers of pyrite. Thus there is a gradation
from the center of the deposit, which is in the main massive pyrite,
to the country rock, which carries only a little pyrite. Comb struc-
ture and druses with crustified banding are lacking. At some places,
notably in the Twin Lead and Tapley mines, small veins of the
sulphides are crumpled parallel to the crumpling of the schist, as
illustrated by figures 2 and 3.
In the Mikn mine, New Hampshire (see p. 50), deposits of the same
general character occur in tAvo overlapping lenses. These two lenses
arc clearly parts of a single ore body which was torn apart during
the process of regional metamorphism. At that time the country
rock was deformed by fiowage and the pyritic deposit by fracture;
FiGURK 2. — Stringer of contorted pjTite in con-
torted rhyolite near the Tapley lode.
CLASSIFICATION OF DEPOSITS.
17
that is, the depth was such that the jDressure due to the weight of the
overlying rocks exceeded the crushing strength of the quartz-chlorite
schist and was inferior to that of the pyrite and quartz. The schistos-
ity of the country rock near by is parallel to the line of separation,
I Foot
J
FIGURE 3. — Quartz-pyrite veinlet leading off from Twin Lead lode. The crumpling of the
• pyrite shows that it is older than the metamorphism of the inclosing Ellsworth schist.
which wraps around the broken ends of the ore body. The fault, if
it be so called, is reverse. The place of separation is' a highly sili-
ceous portion of the lode and one where the ore is highly crumpled.
Perhaps future exploration will show that some of the lodes at Blue
Hill which are said to be overlapping in the underground workings
40 Feet
E^GCRE 4. — Plan of part of the 115-foot level, Milan mine, New Hampshire.
are joined at their ends by thin fissures and that the schistosity of the
country rock along such fissures is parallel to them, as indicated in
figure 4.
The wall rock does not show leaching or changes like those com-
monly resulting fromhot-water action of vein-forming solutions, and
42381°— Bull. 432—10 2
18
SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
if ever changed by the processes of hydrothermal metamorphism, the
changes have been obscured by later regional metamorphism. The
latter process must also have destroyed such features as druses with
crustified banding and comb structures, if they were ever present.
MetamorphisTn. — The behavior of the sulphides during regional
metamorphism is noteworthy. Where the ore is nearly pure sulphide,
composed of pyrite with some chalcopyrite, it is crushed and rece-
mented by pj^rite or by chalcopyrite. It then appears massive and
shows little or no schistosity, and one examining the central part of
the lode only Avould not suppose that it had been deformed with the
metamorphism of the schists. But near the walls, in the lower-grade
ore composed of pyrite, quartz, chlorite, and mica, there is a well-
defined schistosity, as shown in figure 6. From microscopic studies it
is seen that some of the crushed fragments of pyrite have oriented
Figure 5. — Ore from Twin Lead mine, Blue Hill, Maine. The schistosity was developed
after the ore was formed, a, Quartz; 6, pyrite; c, chlorite schist. (Compare fig. 8,
p. 21.)
themselves parallel to the schistosity between the grains of quartz
and chlorite. The crushing is especially well shown where two
crystals of pyrite are pressed against each other or against a grain
of quartz. If the pyrite crystals are surrounded by chlorite or by
mica, they are j)rotected by these yielding minerals, but where two
pyrite crystals touch they are shattered and recemented. This fea-
ture is illustrated by figure 6, which shows crystals of pyrite that
appear in hand specimens to be quite homogeneous. Some perfect
crystals of pyrite are formed, however, from iron sulphide dissolved
and rejorecipitated ; such are found mainly in thin crumpled seams
where movement has been most intense. Under these conditions
cubes and octahedra are developed rather than pyritohedra or pen-
tagonal dodecahedra. The pyrite was deposited in perfect crystals
even under the conditions of great pressure and the jDresence of other
CLASSIFICATION OF DEPOSITS.
19
minerals. The great crystallizing power of pyrite is well known.
It is so great that when pyrite replaces other minerals exactly enough
of their substance is dissolved to make a space for the pyrite. As an
example may be cited the common case of quartzites in which two or
more of the rounded grains of qaartz are half dissolved and one per-
fect pyrite crystal fills completely the space left where the parts of
quartz grains were removed.
It is no easy task to determine the character of these deposits
before they were metamorphosed, but this may be inferred from
their present condition and mineralogical character. The diagnostic
value of the minerals is lessened by the fact that nearly all of them
may be produced under conditions of regional metamorphism wher-
ever the necessary ele-
ments are at hand.
Before metamorphism
the pyritic copper de-
posits of Blue Hill and
Brooksville were pre-
sumably fissure veins
of replacement tyipes
and disseminated ores
along fractured zones.
At the zinc mine at
Deer Isle (see p. 37)
garnet, actinolite, and
calcite are abundant
and are all micro-
scopically banded par-
allel to the schistosity
of the country rock
and to the tablets of
massive sulphides.
This deposit is be-
lieved to be a contact-metamorphic deposit which has been regionally
metamorphosed. An alternate hypothesis is that the garnet and
tremolite were developed by processes of regional metamorphism
when the ore body was subject to the stresses which developed its
schistosity. The garnet, however, is not in the perfect crystals which
usually form under such conditions, but occurs in crumpled bands,
mashed and very highly fractured, alternating with the other min-
erals. (See fig. 7 and PL I, A.) Further, garnet and actinolite are
rare or absent in the Blue Hill copper deposits, which, with respect
to regional metamorphism, have had a similar histor3^ The silver
deposits of the Cape Rozier, Hercules, and Emerson mines, which
from the character of the ore are believed to belong to this very
ildiam.
Figure 6. — Thin section of ore from Milan mine, New
Hampsliire. Tlie pyrite has been shattered and re-
cemented, p, Pyrite ; cp, chalcopyrite ; c, chlorite ;
q, quartz.
20
SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
old group, are not well exposed and their primary origin is not
understood.
Origin. — The source of the solutions which deposited the primary
ores is not known. The youngest rocks of this area which contain
the schistose ores are the greatly metamorphosed Castine intrusives
and flows. All of these ores may have been formed during or at the
close of the volcanic period of the Castine and North Haven erup-
tives, and they may have been formed by solutions contributed by
intrusive rocks such as the North Haven greenstone and the andesites
associated with the Castine formation. The North Haven, which
includes diabase, basic trachyte, and albite-augite syenite, occurs at
some places as dikes
^ ^ * - and sills of approxi-
mately the same age as
the Castine.^ If the
garnetiferous zinc ores
of Deer Isle, which
seem to have been de-
posited in calcareous
tuffs of the Castine for-
mation, are contact-
metamorphic deposits
formed near the mar-
gin of a North Haven
greenstone intrusive,
then the thickness of the Castine above the tuffs must have been
considerable, for such deposits are not formed at shallow depths.
b b
Figure 7. — Thin section of schistose ore from Deer Isle
mine, showing parallel bands of garnet, sericite, and
sulphides, a. Chlorite and sericite ; h, fractured gar-
net ; c, pj'rite, blende, and galena.
DEPOSITS ASSOCIATED WITH GRANITE INTRUSIONS.
The deposits associated with granite intrusions include the Sullivan,
Gouldsborough, and West Franklin mines, the Owen lead deposit at
Blue Hill, and the molybdenum mine at Catherine Hill. The deposits
are (1) fissure veins in schist and diorite near intrusive granite;
(2) molybdenum sulphide ore associated with the pegmatitic phases
of the granite magma; and (3) lead sulphide consolidated with the
rock-making minerals of the granite.
Fissure veins. — The chief metals of the fissure veins are silver and
zinc. The principal minerals are quartz, zinc blende, galena, pyrite,
chalcopyrite, and arsenopyrite, but at the Sullivan mines stephanite,
argentite, native silver, and tetrahedrite are reported to be present.
Pyrrhotite is lacking. In composition and structural features these
lodes contrast strongly with the regionally metamorphosed deposits.
"Smith, G. O., Bastin, E. S., and Brown, C. W., Penobscot Bay folio (No. 149), Geol.
Atlas U. S., U. S. Geol. Survey, 1907, p. 7.
U. S. GEOLOGICAL SURVEY
BULLETIN 432 PLATE I
A. PHOTOMICROGRAPH OF SCHISTOSE ORE FROM DEER ISLE MINE.
B. PHOTOMICROGRAPH OF THIN SECTION OF ORE FROM OWEN LEAD PROSPECT.
MINERALOGY.
21
Although some of them are in the quartz-chlorite (Ellsworth) schist
they cut across the schistosity of that rock and include angular frag-
ments of it. These fragments are slightly rounded by the vein-
forming solutions and are arranged haphazard with respect to
schistosity. Drusy cavities with crustified banding and comb struc-
ture are common. These features are illustrated by figure 8, which
is a sketch of the ore at Sullivan. Comparison of this ore with the
schistose Twin Lead ore illustrated by figure 5 shows many of the
points of difference between deposits associated with granite intru-
sions and those of earlier origin.
The Gouldsborough mine is in quartz diorite, a rock which shows
no regional metamorphism and is believed to be an earlier differentia-
tion from the granite magma. Its age relations with the granite are
shown near the mine, where broken pieces of the diorite are cemented
by granite. The lode is a fissure vein or sheeted zone composed
Figure 8. — Ore from Sullivan mine The schistosity was developed before the ore was
formed, a, Fragments of schist; b, vein quartz. (Compare fig. 5, p. 18.)
of banded sulphides and quartz. Near the lode the hot solutions have
changed the country rock, and much chlorite, some pyrite, epidote,
and sericite have replaced the minerals of the quartz diorite.
The zinc mine at Concord, near Bingham, Somerset County, is a
siliceous deposit occupying the crest of an anticlinal axis. The ore
is not metamorphosed and may belong to the granite period of miner-
alization, but the deposit is isolated and the geology of the surround-
ing area has not been studied with sufficient care to justify an attempt
to classify it.
Molybdenite and lead deposits. — The Catherine Hill molybdenite
deposit (PL III, B) and the Owen lend deposit (PI. I, B) are mag-
matic segregations which belong to this period of mineralization. The
galena and the molybdenite inclose well-shaped crystals of feldspar
rounded on the edges, but clearly idiomorphic, or nearly so. The
sulphides solidified at the time the rock was formed. A similar
22
SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
crystallization of pyrrhotite in peridotite from Knox County has
been described by E. S. Bastin.'^
DEPOSITS ASSOCIATED WITH DIABASE AND TRAP.
The deposits associated with the diabase and trap include those of
the Lubec lead mine, the Denbow Point mine, and the copper and
zinc prospects in Pembroke, all of which are in Washington County
and in the Eastport quadrangle. The country rock is at no place
greatly metamorphosed by pressure and the ores show no' schistosity.
The galena-blende ores at Lubec are deposited in thin fissures and in
brecciated zones. The ores at Pembroke are deposited in vesicular
cavities and in nonpersistent fractures in basic flows, as illustrated by
figure 9.
The deposits of this group show drusy cavities and crustified band-
ing. The minerals of the ore are quartz, dolomite, calcite, galena, zinc
blende, pyrite, chalcopyrite,
a. a, cc CL a. cl bornite, and arsenopyrite.
The oxidized ore is composed
of quartz, limonite, and a
little manganese oxide and
copper carbonate. The Lu-
bec ores carry some silver.
No pyrrhotite is present in
the ores of these deposits and
no massive magnetite, al-
though the crushed ore yields
a trace of magnetic dust —
possibly an oxidation prod-
uct. As a result of the reactions of the vein-forming solutions with
the wall rock much secondary chlorite and calcite were formed but
only a little sericite.
MINERALOGY.
The following list includes the most important minerals of the
deposits, with brief descriptive notes of their occurrence. Only the
most important of the rock-making minerals are mentioned and no
attempt is made to list the minerals of the pegmatites, except those
which are closely related in genesis to some of the ore deposits. The
pegmatites of Maine are to be treated in a forthcoming paper by
E. S. Bastin.
ActinoUte. — Developecl by secondary processes in some of the regionally
metamorphosed schists and intimately associated with the garnetiferous ores at
the Deer Isle mine.
Figure 9. — Brecciated diabase cut by quartz and
sulphides, Pembroke mine, a, Quartz and ore ;
by diabase.
" Pyrrhotitic peridotite from Knox County, Maine — a sulphide ore of igneous origin ;
Jour. Geology, vol. IG, 1908, p. 124.
MINERALOGY. 23
AlMte. — A common constituent of the granite and some other igneous roclvS.
Appears as idiomorphic crystals surrounded by galena at the Owen lead mine
and as crystals surrounded by molybdenite at the Catherine Hill molybdenite
mine.
Apatite. — ^A common accessory constituent of the granite and other igneous
rocks. Crystals of apatite are surrounded by galena in tlie Owen lead prospect.
Argentite. — Reported from the silver mines at Sullivan.
Arsenopyntc. — Present in the copper mines at Blue Hill and in the silver
mines at Sullivan, but not abundant at either place.
Augitc. — Abundant in the basic igneous rocks, but not noted in connection
with any of the ore deposits.
Barite. — Not abundant. A little was noted on the dump at the Deer Isle mine
and at the Sullivan mine.
Biotite. — ^A common constituent of the schist. Is present in the schistose
copper ores.
Bornite. — Not abundant in any of the deposits but appears in some of those
at Blue Hill, at the Lubec lead mine, and at the prospects in Pembroke.
Calcitc. — Rare or absent in the schistose ores at Blue Hill but present in the
Deer Isle zinc ore, in the Lubec lead ores, and in the wall rock near the lodes
along some of the fissure veins.
Cerargyrite. — Reported from the silver mines at Sullivan.
Chalcocitc. — Not abundant in any of the deposits. Sparingly present as
dark films on chalcopyrite at the copper mines near Blue Hill.
Clialcopyrite. — Present in nearly all of the deposits. An important ore min-
eral in the schistose copper ores of Blue Hill.
Chlorite. — Abundantly developed in the schist and intimately associated with
the schistose ores ; also the most abundant mineral formed by metasomatic
processes along the fissure veins in igneous rocks.
Copper, native.— An oxidation product of the copper-bearing sulphides. Re-
ported from the Douglas mine and the Owen mine at Blue Hill.
Cuprite. — Sparingly present in the zone of oxidation of the copper deposits.
Epidote. — Appears with quartz in some small veinlets in Pembroke. Devel-
oped with chlorite and sericite in the quartz diorite wall rock of the Goulds-
borough lode.
Galenn. — Sparingly present in nearly all of the deposits. More abundant at
the Lubec and the Bingham mines. Intergrown with feldspar at the Owen lead
prospect.
Garnet. — Abundantly present in the schistose ores of the Deer Isle mine,
where it has been regionally metamorphosed. Sparingly developed in intruded
rocks near intruding granite and pegmatite.
Gold. — Sparingly present in the Blue Hill mines and reported in small quan-
tities from most of the other mines visited. Occurs sparingly in some river
gravels. Not an abundant ore mineral in Maine.
Graphite. — Occurs in pegmatite and in metamorphosed schists at several
localities.
Gypsum. — Present in ore of Sullivan mine.
Hematite.— E.it'hev hematite or the hydrated oxide turgite is usually present
in the oxidized ore of all groups.
Jiao/i«.— Formed from feldspar and other minerals in the igneous rocks by
reactions with surface waters.
Limonite. — The most abundant mineral in the oxidized ore. Appears near
the surface of nearly all the deposits.
24 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
Magnetite. — Occurs in noticeable quantity in the Blue Hill copper ores and
in the Deer Isle zinc ore. Minute specks are present in the ore of some of the
later silver lodes but only as the merest traces.
Malachite. — Rare in the copper deposits of Blue Hill. Forms on the old
slag dumps, but was not noted in the ore. A little is present in the copper pros-
pects at Pembroke.
Manganese oxide. — Present in the oxidized ore at Blue Hill and occurs in the
Lubec lead ore.
MicrocUne. — See Orthoclase:
Molyddenite. — Present in granite and in pegmatite at Catherine Hill.
Mtiscovitc. — Occurs in the quartz-biotite schist and is associated with the
ores of that rock. Forms as sericite along the silver lodes by metasomatic re-
placement, but not abundantly.
Olivine. — Fresh olivine is abundant in the later trap rocks and decomposed
olivine in the greenstones.
Orthoclase. — Orthoclase and microcline are prominent minerals of the granite
and associated pegmatites.
Pyrite. — The most abundant and a ubiquitous mineral of the ores.
Pyroxene. — Present in the more basic igneous rocks.
Pyrrhotite. — Present in all of the copper ores at Blue Hill and in some of the
lead and zinc ores near by, and sparingly present in the Bingham zinc ore.
Not present in the silver lodes associated with the granite.
Quarts. — Present in most of the igneous rocks, in all of the sedimentary
rocks, and in the ore of all groups of deposits. The pegmatitic quartz con-
tains fluid inclusions.
Rhodochrosite. — Absent in most deposits; a little noted .at the Deer Isle
zinc mine.
Sericite. — See Muscovite.
Siderite. — Gangue mineral at the Pembroke copper prospects.
Sih^er, native. — Reported from the Eggemoggin and Sullivan mines.
Specularite. — Nowhere abundant. Some was noted at the Stewart copper
mine and on the Hercules dump.
8tej)hanite. — Reported from the Sullivan mine.
StiMMe. — Reported from the Sullivan mine and from the copper deposits
near Blue Hill.
Talc. — Present in ore of Sullivan mine.
Tetrahedrite. — Reported from the Sullivan mine.
Tourmaline. — Present in the pegmatite at Mount Mica and at Crocker Hill.
Tremolite. — Developed in the wall rock at the Tapley mine.
Wolframite. — Dr. Charles T. Jackson'* found wolframite (iron-manganese
tungstate) and molybdenite in granite near Blue Hill Falls,
Zinc tlende. — Present in deposits of all groups, but sparingly so in the Blue
Hill copper deposits.
DISTRIBUTION OF OUTCROPS.
In relatively late geologic times the entire State of Maine was
covered with an immense glacier or ice sheet which had slowly in-
vaded it from the northwest. Much of the territory now under the
sea was doubtless overlain by this ice sheet, for it is known to have
extended to far outlying islands. As the climate grew warmer the
ice gradually receded northwestward, but upon the country it had
« First report on the geology of the State of Maine, vol. 1, p. 103.
OXIDATION AND SECONDARY ENRICHMENT. 25
covered it left drift of various types which concealed many outcrops
of rocks and their contained ore deposits. After the ice had gone the
land slowly rose to higher levels above the sea. At some places sea-
worn pebbles are found as much as 225 feet above the present coast."
The emergence of the land was very slow, however, and at times it
remained stationary long enough for imperfect bars, spits, and simi-
lar coast features to be formed.^
In some places in the region of Penobscot Bay, when the land was
about 20 or 25 feet below its present position," there was a note-
worthy halt in the process of elevation, and during this period ter-
races were built by the sea and cliffs were cut in exposed places.
Doubtless the glacial drift was washed away at many places, laying
bare the rocks and ore deposits. Subsequently the land rose 20 or 25
feet. Thus along the ragged seacoast about 25 feet above the present
shore line was exposed a belt which had at favorable places been
lately washed by the waves. Along this belt the rocks are well ex-
posed, and in it many of the ore deposits have been discovered. The^
Deer Isle, Eggemoggin, Hercules, Emerson, Cape Rozier, Sullivan,
Denbow Point, Lubec, and other deposits are near the water's edge,
not more than a few feet above sea level, and some of them doubtless
owe their exposed condition to the washing of the waves in this zone
of delayed emergence. Some of the deposits named were discovered
below high tide and worked by means of cofferdams, but most of them
were found some 10 to 20 feet above high tide.
In many regions creeks and brooks Avhich cut through the over-
lying mantle of soil furnish good exposures of the rocks, and the
banks along such streams are favorable positions to search for out-
crops of ore deposits. In Maine, however, these smaller streams have
been engaged in removing the glacial material left at the compara-
tively late recession of the ice sheet and have not had sufficient time
to do much cutting in the solid rock; consequently, their banks do
not furnish the customary quota of outcrops. At some places, where
the glacial ice with its included stones planed off the country rock,
the latter has not yet disintegrated into soil and still remains bare;
in such places a few deposits have been discovered, among which are
the Tapley mine, in Brooksville, and some of the copper prospects in
Pembroke.
OXIDATION AND SECONDARY ENRICHMENT.
When sulphide ores remain for a long time near the surface of
the earth the oxygenated surface waters react on their minerals.
Oxides, carbonates, and other compounds are formed, and the quartz
" stone, G. H., Mon. U. S. Geol. Survey, vol. 34, 1890, p. 48.
>> Willis, Bailey, Bull. Geol. Soc. America, vol. 14, 1903, p. 205.
<^ Smith, George Otis, Bastin, E. S., and Brown, C. W., Penobscot Bay folio (No. 149),
Geol. Atlas U. S., U. S. Geol. Survey, 1907, p. 13.
26 SOME ORE DEPOSITS IK MAINE AND NEW HAMPSHIRE.
and other difficultly soluble minerals are usually disintegrated. As
a result of these processes the outcrop of a sulphide ore body appears
in general as a mass of iron oxide or of quartz stained with iron oxide
and other oxygen compounds. In cupriferous deposits carbonates
commonly appear at the outcrop, but such are rare in the oxidized
copper ores in Maine.
The depth to which the oxides extend is variable and depends
largely on the shattering or fracturing of the sulphide deposits,
which makes them more pervious to water, and on the length of time
they have been exposed to surface waters. In Maine the deposits are
not greatly fractured, and since glaciation is of relatively recent date
they have not been long exposed to highly oxygenated surface waters.
At many jjlaces the sulphides appear at the very surface, and mixed
oxides and sulphides are very common in the outcrops. At the Doug-
las mine, in the open pit just west of the main shaft, the oxidized
ore ends abruptly along a fracture which cuts the lode 5 or 10 feet
below the outcrop. In the Milan mine (New Hampshire) the depth
of oxidation is greater and the lode is partly oxidized to 40 feet below
the apex, while oxidation along watercourses extends 100 feet below
the surface. Compared with that of deposits in unglaciated regions
oxidation in northern New England is slight.
Where the upper portion of a lode is in the zone of oxygenated
waters, some of the minerals pass into solution. Pyrite and chalco-
pyrite on oxidation yield sulphuric acid and iron and copper sul-
phates. If it happens that a lode is highly shattered below the zone
of oxidation these sulphates are carried downward in solution, and
when they reach a zone in which there is relatively little oxygen they
react with pyrite and chalcopyrite and deposit chalcocite. This proc-
ess is commonly termed secondary enrichment, for it changes the
lower-grade sulphides to richer copper ores. In the Milan mine
the process has operated to some extent to enrich shalloAv chalcopy-
rite and cupriferous pyrite; and masses of these minerals where
fractured are commonly coated with a film of black chalcocite.
Similar ore was observed on the dumps of the Douglas mine, near
Blue Hill, and at other mines near by, but there is no evidence that
this process was carried far. The tight condition of the deposits
and the brief period of exposure to oxygenated waters are unfavor-
able to much sulphide enrichment or to extensive oxidation, and if the
deposits extend downward to great depths the copper content will
not be much lower than it is near the surface.
FUTURE OF THE MINES.
Lead^ zinc, and silver. — It does not appear likely that any of the
lead, zinc, and silver deposits which have been examined will become
important sources of these metals. Possibly some of them could be
worked in a small way by hand sorting and by the more simple
SUMMARY OF GEOLOGIC EESULTS. 27
methods of jiiechanical concentration, but the ore is in the main of
low grade. It is nowhere greatly oxidized and could easily be con-
centrated mechanically, but no ore body yet developed is of sufficient
size to warrant the erection of a plant large enough to work with real
economy. A presumption against the existence of rich deposits asso-
ciated with granite is afforded by the chloritic alterations of the walls
along the veins — alterations supposedly due to the ore-depositing
solutions given off by the granite as it solidified. Chlorite is formed
extensively by regional dynamometamorphic processes, to some ex-
tent in contact metamorphism, and as a secondary mineral by hydro-
thermal metamorphism of the wall rocks along certain productive
lodes in diabase and other basic rocks. Where associated with fissure
veins in acidic rocks, it has generally been formed by the w^eaker ore-
bearing solutions ; and in regions of large and rich deposits it is found
some distance away from the veins, in places where apparently the
solutions had already spent too much of their power to change the
country rock greatly and to deposit ore. Again, near the great vein
deposits the w^all rock has commonly undergone strong sericitization,
pyritization, silicification, and other processes; and these were rela-
tively inactive when the lead, zinc, and silver veins associated with
the intruding granite were formed and were not strongly active when
the ores associated with the trap rocks were deposited.
Copper. — The pyritiferous deposits near Blue Hill are not at pres-
ent sufficiently exposed to warrant an estimate of their value, but a
deposit which is in many respects similar is now successfully worked
at Milan, N. H. (See p. 50.) To judge from the mineral composi-
tion at that place, it would seem that somewhat similar methods could
be applied to the Blue Hill ores. These ores or concentrates from
them would be rich in sulphur and could without doubt be sold
advantageously to acid works. If the paper mills of New England
should ever adopt the practice followed at some European plants,
they could make their sulphur dioxide at a lower cost for the raw
material from pyrite than from native sulphur, a large tonnage of
which is now utilized in paper manufacture. The schistose garnetif-
erous sulphide ore at Deer Isle has proved refractory to metallurgical
treatment, but possibly one of the newer methods of oil flotation could
be successfully employed to separate the garnet from the sulphides
if the amount of ore exposed is sufficient to warrant an installation.
SUMMAaY OF GEOLOGIC EVENTS AS RELATED TO ORE DEPOSITS.
From studies of the geology of the Penobscot Bay quadrangle,'^ the
Perry Basin,^ and other areas, and from the observed relations of the
ore deposits, the geologic events related below are deduced.
"Smith, G. O., Bastin, B. S., and Brown, C. W., Penobscot Bay folio (No. 149), Geol.
Atlas U. S., U. S. Geol. Survey, 1907.
" Smith, G. O., and White, David. Prof. Paper U. S. Geol. Survey No. 35, 1905.
28 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
Pre-G amhrian and Cambrian time. — In pre- Cambrian or possibly
in early Cambrian time a series of siliceous shales and impure sand-
stones were laid down in extensive beds and were subjected to re-
gional metamorphism. Later, probably in Cambrian time, the im-
pure sand which now forms the slates of the Islesboro formation was
deposited. During the deposition of this formation great volcanic
activity prevailed; the acidic Castine rocks, which included both
flows and dikes and some calcareous water-laid tuffs, were formed.
These were followed very closely or perhaps in part were accompanied
by the North Haven eruptives. These North Haven diabases, basic
trachytes, and albite-augite syenites included both effusive and intru-
sive bodies. The garnetiferous zinc ores at the Deer Isle mine, which
are in a calcareous phase of the Castine near the contact of the North
Haven greenstone, were probably formed by processes of contact
metamorphism during North Haven time, and part or all of the Blue
Hill and Brooksville pyritiferous copper ores are believed to have
been formed at the same period or in connection with the Castine
eruptions. Near the close of the period regarded as Cambrian and
following closely the igneous activity, the Coombs limestone, a mem-
ber of the Islesboro formation, the Battle quartzite, and the slates of
the Penobscot formation were successively laid down.
After the eruptions, after the copper and the zinc ores were de-
posited, and after the Penobscot beds, which later became slates, were
laid down, the region was subjected to profound dynamic metamor-
phism. A schistose structure was developed in all of the rocks, but
is most marked in those containing the most clay. The ore bodies
also took on a schistose structure. As a result of this, in the Deer Isle
zinc deposit garnet, amphibole, quartz, sulphides, and magnetite were
compressed into thin crumpled parallel bands. The copper deposits
also were greatly affected, but since these were simpler in mineral
composition the resulting deposits were different. At the center
of the deposits the large and relatively j)ure masses of pyrite were
broken and recemented with pyrite and chalcoi^yrite. Where there
was a higher percentage of quartz with the pyrite the two min-
erals were broken into unequidimensional fragments and these
oriented themselves in lines parallel with the schistosity. Where
considerable clayey material was present chlorite and the micas
formed in great abundance and oriented themselves with their long
directions nearly parallel with the schistosity and parallel to the
long dimensions of quartz and pyrite fragments. AVhere a pyrite
crystal was protected by a cover of clayey material it did not break,
but the micaceous minerals formed inclosing spheres around it and
bent to accommodate themselves to it; but where such a pyrite
crystal Avas pushed through the chlorite against another crystal of
pyrite, both were shattered. There was much recrystallization and
SUMMARY OF GEOLOGIC KKSULTri. 29
some pyrite was redeposited as perfect crystals. Quartz se(Miis also
to have been dissolved and reprecipitated to some extent, but not in
crystal form. Dnring metamorphism some of the ore bodies were
probably separated by a peculiar kind of faulting, which must have
taken place at a depth that was in the zone of flow for the wall
rock and the zone of fracture for the ore. Such a fault, as illustrated
by the Milan mine (see p. 50), is strikingly sigmoidal and laps
around both of the ends of the broken ore body, the schistosity fol-
lowing its complexly curving plane, as shown by figure 4. The
overlapping lenses which are said to constitute some of the Blue Hill
deposits probably resulted from similar movements. Just when
these events happened is not known, but they were before the begin-
ning of the deposition of the Ames Knob formation, which lies un-
conformably above the metamorphosed series. The Ames Knob is
of Silurian age (Niagaran) and is not metamorphosed, its lowest
member being a basal conglomerate which contains well-rounded
pebbles of black and green slates, quartzites, and vein quartz." The
metamorphosed rocks and ore deposits are therefore older than the
Silurian, but how much older is not known.
Silvrian time. — ^AHiile the Silurian rocks were being deposited
volcanic forces again became active. The Thorofare andesite was
erupted and was followed by the Vinalhaven rhyolite. At about this
time gentle folding and some faulting took place, accompanied or
followed by the great intrusions of granite and diorite. The intruded
rocks were metamorphosed to some extent, though not profoundly, by
the gases and solutions given off. The granite intrusions all along
the coast were probably formed at about the same time, and if so
they are of post-Niagaran or early Devonian age, for pebbles of the
granite are found in the late Devonian (Perry formation). It seems
that the granites were in the main poor in metals, but some of their
pegmatitic phases carried a little molybdenum sulphide, w^hich was
deposited when the pegmatites solidified. Quartz veins were de-
posited also by solutions which originated in the granite. Some of
these veins were barren, but some carried ores of silver, zinc, and
lead. The Sullivan silver veins, which are in the Ellsworth schist,
were deposited at this time, and the Gouldsborough zinc-silver lode
in diorite is presumably of the same age. The mineralizing solutions
altered the wall rock to chlorite, epidote, and sericite, but this action
was not intense. The galena-feldspar ore in a prospect on the Owen
farm at Blue Hill appears to have consolidated directly from the
granite.
Devonian time. — After the granite had solidified it was eroded ;
and above it the lower conglomerate member of the Perry formation
was laid down in late Devonian time. Subsequently basic lavas were
« Smith, Bastin, and Brown, folio 149, 1907, p. 4.
30 SOME OKE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
extra vasated upon these, and upon the lavas Denovian sandstones were
deposited, which were in turn overflowed by vesicular basic lavas.
In connection with the same general period of basic eruptives, and
probably in late Devonian time, the Lubec, Denbow Point, and Fern-
broke lead and zinc deposits are believed to have been formed. Still
later — probably in Mesozoic time — basaltic dikes cut the various
formations; at Concord, in Somerset County, an ore deposit which
in general character most closely resembles those associated with the
granular intrusives is cut by such a dike.
Quaternary time. — Other events that affected the ore deposits in
Mesozoic or in Tertiary time are not known. If the deposits exposed
to Aveathering were deeply oxidized during those periods then the
oxidized portions were planed off by the great ice sheet which
covered the country in Pleistocene time. In Recent time, however,
since the retreat of the ice, the sea has cut cliffs in which many of
the deposits are exjDOsecl, and as a result the seashore has become a
favorable j)lace for outcrops. The copper lodes, where fractured,
have been to a very tri^dal extent leached by descending surface
waters, which have dejaosited chalcocite films on the older sulphides,
but these lodes were presumably so completely recemented during the
period of regional metamorphism and have been disturbed so little
since that time that they have not been greatly affected by the
processes of chalcocitization. Some oxidation has taken place, but
as. a rule it has extended to only slight depths — generally to not more
than a few feet below the outcrop.
DESCRIPTIONS OF MINES.
HANCOCK COUNTY.
GENERAL STATEMENT.
The southwestern part of Plancock County has been geologically
mapped in detail by George Otis Smith, E. S. Bastifi, and C. W.
Brown in the Penobscot Bay folio (No. 149) of the Geologic
Atlas of the United States, published by the United States Geolog-
ical Survey. Plate II of the present paper is a reproduction of a part
of the geologic map of this folio, with the addition of symbols indi-
cating the positions of the mines in the district. Figure 10 is a section
showing the relations of the rocks along the line A-A' in the plate,
but extending beyond it, and figure 11 is a section along the line B-B'.
The principal rocks with which the ores are associated are the
Ellsworth schist, the schistose volcanic rocks, and the granite and
closely related diorite. The relatively small area of Ellsworth schist
at Blue Hill includes nearly all of the schistose dejDOsits of pyritic
copper ores. A large area of quartzose schist extends northwestward
U. S. GEOLOGICAL SURVEY
BULLETIN 432 PLATE II
II- 1 T H
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GBOIiOGIC MAP or THE MINERALIZED AREA OF BLUEHILL, BROOKSVILIiE, DEER ISLE,
AND CASTINE, MAENE
Scale r260oo
H.M.Wilson, Geographer In charg.
Topograph_y by U.S. Coast and
Geodetic Survey, W. H.Lovell,and
Hersey fvlunroe.
Triangulation by US. Coast and
Geodetic Survey
Surveyed in 1900-1903.
SEDIMENTARY ROCKS
&; 5 KiloiDLeljers
Geology by George Otis Smith,
E.S.Bastin.and C.W.Brown.
Surveyed in 1902-1904.
Conto-ux* irrtexTral 20 feet.
nation is m&an een, leveX.
1909
LEGEND
IGNEOUS ROCKS
CAMBRIAN 7
€i
CAMBRIAN OR PRE-CAMBRIAN
A
^
^
ev/
DEVONIAN ?
CAMBRIAN ?
CoTttempcfraneous ivitTi Tippisrjiart
OT Isleshoro formatioTi
^fer
Islesboro foimaiioii EUswortb. sdrLst Biotite drauite Dioiite, diabcLSe, Seipentine
(slca^san^adhtstslocaHv fcrujnf>le^ gr^im. onA fiiju^Tn,e^zU77i.,a7uiooars& aXLcL ^ 8Lbl>rO
Noilli Haven. Castme fonxia.tLon
greeiLS>XOILe ^iu.oixujrnng as flovs.
anAoocxiawnjaZly pur&
^ Mne 5< Qioarry cX. Grav^el pit
HANCOCK COUNTY.
from Fi-enchniaii Bay along Union River far to the
north of Ellsworth. This area includes the mines at
Sullivan and Franklin.
The schistose igneous rocks which
belong to the Castine formation cover
extensive areas in the western part of
the region represented on Plate 11.
The Tapley mine, which in many re-
spects resembles the Blue Hill copper
deposits, is inclosed in the Castine, and
the Deer Isle, Eggemoggin, Cape
Rozier, Hercules, Emerson, and other
deposits are in the same formation.
The granites and associated diorite
which are intrusive in the schistose
rocks cover a large part of the area
represented on Plate II, but in this
area the only deposit known which is
genetically related to the granular
rocks is at the Owen lead prospect.
In the eastern part of the county, at
Sullivan and at Franklin, fissure veins
of silver ore which cut the schist near
granite contacts have been deposited
by solutions which are believed to have
had their origin in the granite. Still
farther east, the Gouldsborough, a lode
of argentiferous zinc blende in diorite
is supposed to have had a similar gene-
sis, and just east of the Hancock
County line at Cherryfield a zinc de-
posit is inclosed in schist not far from
granite to which it may be genetically
related. The molybdenite deposits of
Catherine Hill are associated with peg-
matite veins which cut the granite.
DOUGLAS MINE.
,t^ The Douglas mine, located about 2
, ^ miles southwest of Blue Hill village,
^ ^'^ is owned by interests identified with
the Pittsburg and Montana Company, of Butte. The
>^^:
*. a
mine was opened in 1878 and was worked until 1883
and is said to have produced between two and three
1
SSjs
32 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
million pounds of copper which yielded about $300,000. It was
reopened in 1908 and sampled by its present owners. A two-com-
partment shaft inclined 47° is sunk 245 feet on the incline. A second
two-compartment shaft, about 150 feet to the east, is sunk to a depth
of 75 feet. Both were under water when the mine was visited. The
deep shaft is equipped with steam power and skip. On the surface
are numerous heaps of roasted ore and the ruins of a concentrator,
blast furnace, precipitation plant, and refining furnace. The deposit
is a lode said to be from 12 to 20 feet wide, striking eastward and
dipping about 45° S.
An analysis of the better grade of ore made for the company by
S. P. Sharpies, of Boston, is given below :
Analysis of copper ore from the Douglas mine.
Si02 35. 8
Fe -___ 25. 9
CaO .13 •
Mn . 52
Al=03 - 3. 11
S -_ 28
Cul 5. 88
99.34
This ore carries 0.01 ounce gold and 1.17 ounces silver to the ton.
The country rock is a rather siliceous phase of the Ellsworth schist
and is composed of quartz, muscovite, and biotite, with pyrite scat-
tered liberally through it. Where exposed in an open cut a few feet
west of the main shaft the lode follows the schistositj^ of the country
rock. The ore minerals observed in the pit and on the dump are
pyrite, chalcopyrite, pyrrhotite, chalcocite, arsenopyrite, zinc blende,
magnetite, and cuprite. Stibnite. tennantite, and tetrahedrite have
also been reported." The gangue minerals, which in places are
banded with the sulphides, are quartz, sericite, biotite, and chlorite.
A little molybdenite is present, with pyrite and muscovite. Thin
sheets of native copper are reported to have formed in joint seams of
the ore. Oxidation in the open pit is nearly complete to a dejoth of
5 feet and ends at a prominent joint plane which dips to the south
at a very low angle.
TWIN LEAD MINE.
The Twin Lead mine is on the Sargentville road about 1|- miles
southwest of Blue Hill. A three-compartment inclined shaft now
filled with water is reported to be 200 feet deep. The lode has been
" Smock, J. C, Mineral Resources U. S. for 1882, U. S. Geol. Survey, 1883, p. 687.
Bartlett, F. L., Mines of Maine, p. 23.
HANCOCK COUNTY. 33
stoped out open cast to a depth of 12 feet for about 70 feet along the
strike. The ruins of a smelter and small slag dump show that some
ore has been treated. The lode, which is about 10 feet wide, is in the
Ellsworth formation and parallels the schistosity, striking N. 77° E.
and dipping about 45° S. The ore minerals are pyrite, pyrrhotite,
magnetite, chalcopyrite, and a little bornite. The gangue minerals
are quartz, sericite, biotite, and chlorite. The sulphides outcrop at
the surface and oxidation is inconsiderable. The pyrite is dissem-
inated through the rock and in bands parallel to the schistosity, but
lenses of ore, consisting mainly of pyrite, chalcopyrite, and quartz,
are found here and there in the lode. A stringer of pyrite, making
off from the main lode, is shown in figure 3; its associations show
that the quartz and pyrite are older than the metamorphism of the
schist, a fact also indicated by the arrangement of the minerals in
the lower-grade ore.
BLUE HILL MINE.
The Blue Hill mine is located 1,050 feet west of the Tw^in Lead
mine, on the opposite side of the road. Large dumps of ore and coun-
try rock similar to that of the Twan Lead surround the ruins of a
shaft, and roasted heaps of ore lie near by. Near the mine are the
ruins of a concentrating mill, and below this are the ruins of a smelter
and slag dump. The lode is not accessible above or under ground.
At the low hill just south of the mine a 75-foot tunnel is driven east-
ward in pyrite-bearing schist cut by large masses of white quartz.
Southwest of this tunnel, on the southwest slope of the hill on which
the Blue Hill mine is situated, a deep open cut about 75 feet long and
10 to 15 feet wide is driven S. 85° E. into the hillside. The country
rock is quartzite impregnated with pyri^^e and cut by numerous
closely spaced veinlets of pyrite. It carries also some large masses
of nearly pure jjyrite and some chalcopyrite.
STEWART 3IINE.
The Stewart mine is southeast of "Third Pond, between this and
Second Pond and about 100 yards northeast of the Douglas mine. A
two-compartment shaft said to be 150 feet deep but now filled with
water is sunk southward at an inclination of 57° on an eastward-
striking lode. The ore on the dump is similar to that of the Twin
Lead but is more siliceous. About 150 feet north of the shaft an-
other lode about 10 feet wide strikes S. 87° E. and dips 70° to 80°
S. ; it is opened in a long, deep cut exposing a great mass of pyritif-
erous rock. The country rock, which is the Ellsworth schist, con-
tains considerable biotite, but is more siliceous than at the Blue Hill
and Twin Lead. Actinolite, tremolite, biotite, sericite, chlorite, and
zircon are microscopically visible. Near the lode the quartzose schist
42381°— Bull. 432—10 3
34 SOME OEE DEPOSITS IX MAIXE AXD XEW HAMPSHIEE.
carries considerable pyrite and some clialcopvrite, magnetite, and
pvrrhotite. The trend of the deposit agrees with the schistosity of
the rock, and as at the Bhie Hill and the Twin Lead the pyrite bands
are crumpled like the silicates, showing that the ore was deposited
before the regional metamorphism of the country.
MAMMOTH MINE.
The Mammoth mine is located on the south shore of Second Pond,
one-half mile from the Douglas. A vertical shaft, now full of water,
is said to be 100 feet deep. The country rock is Ellsworth schist,
here very quartzitic. The gangue is quartz, biotite, muscovite, and
actinolite. The ore minerals are pyrite. chalcopyrite, pyrrhotite. and
specularite. with a very small amount of zinc blende and galena.
On the dump are several hundred tons of highly pyritiferous rock
which carries a noticeable amount of the copper sulphides.
OWEX MIXE.
The Owen mine is located on the west side of Second Pond, half
a mile southwest of the Douglas. The country rock is a siliceous
phase of the Ellsworth schist with a schistosity that strikes S. 82° E.
and dips 45° S. A pit 2.5 feet long and 12 feet wide is sunk in sul-
phide ore and pyritiferous quartzite to a depth of 30 feet. The
workings do not show the direction of the lode. The minerals are
quartz, biotite, sericite. pyrite. chalcopyrite, pyrrhotite, and mag-
netite. According to Mr. Arthur Owen thin sheets of native copper
have been found in joint planes of the rock. The ore is said to carry
more than 3 per cent of copper.
OWEX LEAD PROSPECT.
The Owen lead prospect is one-half mile west of the Mammoth
copper mine and north of the granite batholith which cuts siliceous
Ellsworth schist near by. In 1909 the small pit 20 feet deep was
full of water. The Ellsworth here is composed of quartz, biotite,
muscovite, and other minerals and is cut by dikes of granite wliich
make off from the large mass. There is no pronounced contact meta-
morphism of the schists; no garnet appears to have been formed;
actinolite is rather more abundant than elsewhere; magnetite and
pyrrhotite are developed but are not more abundant than at other
places in the schist a mile or more away from the contact, where they
have formed through d}Tiamometamorphism. In one of the small
granite dikes there is considerable galena, a little pyrite. and some
chalcopyrite, all of the sulphides being intergrown with feldspar,
quartz, biotite, and muscovite. Magnetite or pyrrhotite. which are
common in the copper ores, are not present in the lead ore.
HANCOCK COUXTT. 36
TYliile the deposit appears to be small, the genesis of the ore is
of peculiar interest. The granite near by is medium grained and
is composed of quartz, feldspar, biotite, and a little sericite. The
feldspars are orthoclase. microcline, and a little albite. The galena-
bearing granite is not coarse like most pegmatites but is of medium
grain like all the granite near bj'. It has the same minerals in the
same proportion except that albite, a small amount of which is
present in the granite, is even less abundant in the ore. The galena,
which in some specimens makes up one-fourth or more of the mass,
is intergrown with the feldspars and surrounds well-formed idio-
morphic feldspar crystals, the sharp corners of which have been
rounded off before the galena solidified. A little apatite is also
inclosed in galena and some chalcopyrite is intergrown with galena.
The structure is the same as in some diabases, where feldspar crystals
are surrounded by a matrix of augite. but in the granite here galena
takes the place of augite. A photomicrogi'aph of a thin section
of this ore is shown in Plate I. B. Xone of the minerals are highly
altered, but some chlorite is developed by decomposition of biotite and
the feldsj)ar is slightly clouded by decomposition to kaolin. The
white mica present is mainly or altogether primary. The ore is
clearly the consolidation of a molten magma.
GRAKGER INIIXE.
At the Granger mine, about three-fourths mile south of Blue Hill,
a shaft, now inaccessible, is sunk in the Ellsworth schist. In the
ore exposed on the dmup the gangue minerals are quartz, biotite,
chlorite, and sericite. The sidphides noted are pyrite. chalcopyrite,
and bornite.
WEIL FREDDIE MIXE.
The Weil Freddie mine is a few rods east of the village at Blue
Hill Falls,-on the north shore of the bay. An inaccessible shaft, re-
ported to be 100 feet deep, is sunk in pyritiferous Ellsworth schist
which carries some copper j^yrite.
TAPLEY MINE.
The Tapley mine is on the farm of Charles P. Tapley. about 2^
miles southwest of Brooksvilie. It was opened about thirty years
ago and a small amount of ore has been shipped for experimental pur-
poses. The mine changed ownership in 1907 and some development
work was then done, but these operations were soon suspended, and in
1909. when the property was visited, the mine was idle and the under-
ground workings full of water. A shaft is sunk on the lode to a
depth of SO feet and according to report some 200 feet of drifts and
36 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIEE.
crosscuts are turned from it. The deposit was exposed at several
places in open cuts.
The country rock is the Castine formation, which is here, in the
main, a rhyolitic breccia, but which locally includes a dark rock,
presumably andesite. Both of these rocks are regionally meta-
morphosed, with the development of secondary biotite, sericite, and
tremolite. Small colorless garnets are developed also in the andesite.
Some of the rhyolite contains mmierous specks of microscopic magnet-
ite and in hand specimens is as dark as the andesite. The schistosity
of this rock, which though not pronounced is well defined, strikes
northeastward. The rhyolite is at some places strongly plicated and
cut by quartz veinlets which cross its schistosity. Northwest of the
lode a dike of basalt only slightly metamorphosed cuts the Castine.
The deposits outcrop on a glaciated surface. For 500 feet along the
lode the ground is cleared and open cuts are dug at several places.
The lode strikes N. 47° E., parallel to the schistosity, and is a wide
zone of shattered and altered rhyolite. The sulphides are p^^rite and
chalcop3'rite, both of which are found at the very surface; films of
limonite, hematite, cuprite, and bornite appear in small amount in
the cracks of the ore, which is not highly shattered. The ore
includes fragments of the country rock which are slightly silicified,
but the lum2:>s of pyrite ore on the dump contain but little quartz.
These fragments contain much more sericite and chlorite than the
country rock a few feet from the vein. Some of the ore in the open
pits is rhyolite which contains secondary tremolite, sericite, biotite,
and chlorite, with flakes and specks of pyrite, the latter constituting
perhaps 10 per cent of the mass. A little magnetite and pyrrhotite
is present. Some of the ore impregnated with pyrite shoAvs laminated
sericite and quartz, and some of the chalcopyrite is feebly laminated
parallel to the micaceous sheen which shows when the ore is held in
suitable position, suggesting that the sulphides were formed before
the regional metamorphosing processes had ceased operation. This
relationship is indicated also by the crumpled stringers of pyrite
which are found near the lode. One of these is shown in figure 2.
EGGEMOGGIN MINE.
The Eggemoggin mine is at tide water on Bj^ard Point, about a
mile west of Sargentville. Two shafts, now inaccessible, are sunk in
devitrified rhyolite breccia of the Castine formation. The lode is
not exposed, but the dump showed altered rhyolite impregnated with
sulphide and galena. Some of it is strongly sheeted and cut by par-
allel stringers of white quartz, which also carries sulphides. The
principal minerals are quartz, sericite, pyrite, arsenopyrite, chalcopy-
rite, galena, and zinc blende. The ore is reported to carry good
HANCOCK COUNTY. 37
values in silver. Native silver is said to have been present. Accord-
ing to report, shipments of ore were made in the late eighties, but the
mine has not been worked for many years. The ruins of an old
metallurgical plant stand near by.
DEER ISLE MINE.
The Deer Isle mine is located at tide water on Dunham Point, about
3 miles west of Deer Isle village. This mine was first worked in the
seventies and was reopened in 1907, since when it has produced about
900 tons of ore. A shaft is sunk on the lode at an inclination of 45°
to a depth of 260 feet, and on the 200-foot level drifts about 100 feet
long are turned in either direction. Near the shaft stopes are carried
up within a few feet of the surface. When the mine was visited stopes
below the 100-foot level were inaccessible.
The mine is in the Castine formation, presumably an altered por-
phyritic rock with phases which were probably calcareous water-laid
tuff. The North Haven greenstone outcrops near by and is regarded
as of approximately the same age as the Castine formation."
The lode follows the schistosity of the country rock, striking from
N. 22° E. to N. 70° E., and dips from 45° to 65° N. The schist is
heavily impregnated with sulphides for a width of 1 to 8 feet.
Sheets of pure sulphide an inch or two wide persist for several feet
along the dip and strike and are overlapped by similar sheets. The
rock between these is composed of innumerable paper-thin sheets of
alternating sulphide and garnet.
The sulphides are steel-colored zinc blende, pyrite, galena, and
chalcopyrite. Intergrown intimately with them is a considerable
amount of magnetite. The gangue minerals are garnet, actinolite,
sericite, calcite, chlorite, quartz, and rhodochrosite ; a little barite
was noted on the dump. Figure 7 is a sketch of a thin section of the
ore, showing parallel bands of garnet, sericite, and sulphide. With-
out doubt the deposit has been regionally metamorphosed since it
was formed, and the highly schistose structure of the lode, which
parallels that of the country rock, has resulted from the same dy-
namic forces that developed the schistosity in the country rock. Ac-
cording to George H. Holden the high-grade ore carries zinc 30
per cent, lead 16 per cent, silica 12 per cent, copper 2^ per cent, and
gold $2.50 a ton. The minerals with the exception of barite and
rhodochrosite are those commonly found in contact-metamorphic
deposits, but they have been crushed or redeposited by regional meta-
morphism.
The sulphides have been crushed, recemented, and in part re-
crystallized. The chlorite and mica seem to have been completely
"Smith, Bastin, and Brown, folio 149, Geol. Atlas U. S., p. 5.
38 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
dissolved and recrystallized with longer axes parallel to the schis-
tosity and to the orientation of the lode. The garnet is so highly
fractured that in places it is almost opaque in thin section when the
nicols are not crossed. None of the garnet shows the crystal form.
Garnet, as is well known, is formed in igneous rocks, in contact -meta-
morphic deposits in some deep veins, and by regional metamorphism.
In igneous rocks it is nearly always idiomorphic. In contact-meta-
morphic deposits it is either massive or idiomorphic and very often
shows such optical anomalies as double refracting rings. It may
have schistose structure when it replaces schists, but it is not highly
fractured like the Deer Isle garnets, and some crystals usually have
the crystal outline or else show the double refracting rings. In the
veins of the deep zone it is usually idiomorphic. The garnet of the
Deer Isle mine is not idiomorphic, is greatly crushed, and does not
show double refracting rings. Under the microscope it has the color
and general appearance of andradite and without much doubt is con-
tact-metamorphic garnet which has been regionally metamorphosed
by pressure. (See fig. 7 and PI. I, ^.)
CAPE ROZIER MINE.
The Cape Rozier mine is at Harborside, across the harbor from
Castine. The country rock is schistose pyroclastic tuff of the Castine
formation. This is cut by diorite, which shows no schistosity.
On the dump are fragments of the Castine formation cut by thin
sheets of pyrite and chalcopyrite and stained with green copper car-
bonate. The two shafts are inaccessible. Some ore on the dump of
upper shaft is composed of calcite, zinc blende, pyrite, and chalcopy-
rite. The ore observed shows no schistosity.
HERCULES MINE.
The Hercules mine is between Penobscot and Castine, just above
the Bagaduce Narrows. A shaft sunk at tide water is now submerged.
The country rock is the Castine formation, which, near the ore body,
is highly silicified and somewhat sericitized. Some ore on the dump
shows quartz, sericite, zinc blende, galena, chalcopyrite, pyrite, pyr-
rhotite, and specularite.
JONES & DODGE MINE,
The Jones & Dodge mine is one-half mile southwest of the Her-
cules, on the south shore of the Bagaduce Narrows. The country
rock is the pyroclastic phase of the Castine formation, which at the
mine shows a schistosity striking northward. In the dark biotitic
portion of the country rock certain bands carry small amounts of
pyrite, chalcopyrite, galena, and zinc blende.
HANCOCK COUNTY.
39
EMERSON MINE.
The Emerson mine is near the Castine ferry on the west shore of
Bagaduce River. A two-compartment shaft, sunk near the shore,
is under water. The country rock shown on the dump is devitrified
rhyolite. Some of this is brecciated and has sulphide ore deposited
between its fragments. The amount of ore on the dump is very small.
The minerals noted are galena, zinc blende, pyrite, magnetite, and
pyrrhotite.
SULLIVAN, WAUKEAG, AND PINE TREE ]\riNES.
At West Sullivan, east of Frenchman Bay, several mines are located
along tide water. These include the Sullivan, Waukeag, and Pine Tree
Granite
Figure 12. — Cross section of the Sullivan mine. (After Kempton.)
mines, all of which, according to report, are on the same lode. The
Sullivan lode, which was discovered in 1877, outcrops below high tide.
A cofferdam was built and this and the Waukeag mines were worked
from 1878 to 1884. The Waukeag, which operated a 14-stamp mill
and smelting furnace, is reported to have produced 25 tons of silver-
lead bullion. All the mines were inaccessible in 1909.
The country rock is dark-gray micaceous schist, probably the
Ellsworth. Near the mines the schistosity strikes S. 75° E. and is
practically vertical. At places it is cut by a dark rock, presumably
a diorite. A few rods west of the Waukeag shaft are large outcrops
of medium-grained granite, composed of quartz, feldspar, biotite, and
muscovite. The Waukeag shaft, which is vertical, is reported to be
410 feet deep. A second shaft near by on the .same property is 60 feet
deep. On the Sullivan, about 180 feet southeast of the Waukeag, a
shaft is driven 290 feet on a steep incline to the northeast. A cross
section of the vein, after C. W. Kempton, is shown in figure 12. The
40 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
Milton shaft, about one-fourth mile clown the bay and along the strike
of the lode, is sunk to a depth reported to be 260 feet. According to
report the lode was not encountered in a 400-foot crosscut to the
southwest.
To judge from the ore on the dump the deposit is a clean-cut vein
filling a fissure in the schist and is not regionally metamorphosed.
The gangue is quartz, barite, talc, and gypsum ; the sulphides, which
are not abundant in the gangue, include zinc blende, galena, pyrite,
chalcopyrite, arsenopyrite, and a graj^ sulphide which is probably brit-
tle silver. Threads of native silver are said to have been found 10 feet
below the surface. Magnetite, specularite, and pyrrhotite are absent.
The quartz is usually massive, but is also found as acicular crystals
pointing to the center of a druse. Brecciated fragments of the
schistose country rock are included in the ore and the rounded edges
of these show that they were partly dissolved by the ore-depositing
solutions. These relations are shown in figure 8. The schist is not
strongly leached near the lode, but chlorite and sericite have devel-
oped through metasomatic processes.
The banded ore is not schistose like the pyritic copper ores in the
Ellsworth schist and is clearly of later age ; it was probably formed
at the time of the intrusion of the granite.
C. W. Kempton," who was engaged as a mining engineer at Sulli-
van in 1877, gives the following information relating to the Sullivan
mine :
Proceeding witb the shaft, at about 30 feet deptli, the vein, composed of
quartz, with more or less slate highly imi)regnated with sulphides, was found
to be 4 feet wide. * * * The ore is essentially silver, sulphides and native,
in quartz and slaty gangues, with slight amounts of iron, zinc, etc., as sul-
phides, and also galena. Of the silver minerals, stromeyerite is most plentiful,
stephanite next, argentite (silver glance), common, native silver in flakes very
plenty, threads frequent, lumps occasional.
Kub.v silver is exceedingly rare; antimonial silver has been found. The
occasional yellow copper sulphide met with has a peculiar luster and runs
very rich in silver.
As stated above, the course of the vein is from northwest to southeast, with
the strike of the slate running parallel to the line of contact of the granite.
The vein is in the slate, dipping at an angle of 70° from the horizon, north-
easterly, toward the granite, which it probably reaches in less than a thousand
feet. The slate also dips toward the granite at this place about 37° from
horizontal, although at some other places not more than 12°.
At the contact of the slate and granite the latter often penetrates the bed-
ding of the slate, in known instances nearly 200 feet. The granite is much
cut up by dikes of black trap, which also runs into the slate, faulting the vein
in several ))l;ices.-
GOULDSBOROUGH MINE.
The Gouldsborough mine is in the town of Gouldsborough, about
9 miles southeast of West Sullivan. A shaft 150 feet deep is sunk on
"Trans. Am. Inst. Min. Eng., vol. 7. 1S78, p. 349.
HANCOCK COUNTY. 41
the lode and a drift is driven nortljweslward 75 feet from the 100-foot
level. The mine is now under water. On the surface the vein is
stoped, underhand, in an open cut 150 feet long, which reaches a
maximum depth of about 50 feet. In the early eighties some ore was
shipped. The countr}^ rock is dark quartz diorite, which shows no
sign of contortion or regional metamorphism. One mile to the south
there are large areas of granite and near the mine the brecciated
diorite is cut by granite veinlets. Near the lode the diorite is
somewhat decomposed and locally it is brecciated and cemented by
rhodochrosite.
The lode is a fissure vein which strikes N. 63° E, and is approxi-
mately vertical. It varies in width from 6 inches to 2 feet and is
composed of banded quartz and sulphides, with angular slabs of
country rock. The metalliferous minerals are galena, chalcopyrite,
pyrite, zinc blende, and a very small amount of magnetite. The pro-
portion of sulphide to quartz is high and the ore is said to carry
considerable silver. The hydrothermal metamorj)hism of the wall
rock is clearly shown. The quartz diorite is a medium-grained rock,
is very fresh, and is composed of oligoclase, andesine, hornblende,
biotite, quartz, orthoclase, and pyrite. Within a few feet of the lode
this is altered to a rock composed of chlorite, sericite, epidote, quartz,
and pyrite. The chloritization does not extend far from the lode. A
rod or two away a brecciated quartz diorite is, as already stated, ce-
mented by coarse granite. The quartz diorite is certain!}^ older than
the granite, and the granite is probably the source of the ores.
The outcrop is partly oxidized, but sulphides appear within a few
feet of the surface. The banding of the ore, the open druses parallel
to bands, the brecciation of diorite and its inclosure in ore, the absence
of crenulation and foliation in the vein, and the characteristic hydro-
thermal metamorphism of the wall rock show that the deposit belongs
to the class which postdates regional metamorphism.
FRANKLIN EXTENSION MINE.
The Franklin Extension mine is 2 miles west of Franklin station
and one-eighth mile west of West Franklin. The lode is a narrow
fissure vein in contorted schist, presumably the Ellsworth. It strikes
]Sr. 18° E. and is approximately vertical. Two shafts, said to be on
the same lode, are sunk about 300 feet apart. The ore is composed of
quartz, arsenopyrite, galena, and pyrite. Granite, cutting the Ells-
worth schist, is exposed within a few feet of the lode. The deposit,
which is said to carry silver, is banded and shows comb structure. It
is clearly of later age than the metamorphism of the schist.
COPPEROPOLIS MINE.
The Copperopolis mine is near Egypt, 4 miles west of Franklin
station. Two hundred yards west of the mine house three pits are
42 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
sunk in the contorted Ellsworth schist, which carries seams of quartz
and pyrite with stains of copper carbonate. The Harvey Elliott
prospect is about 300 yards east of the mine house. The shaft was
under water Avhen visited, but to judge from the dump the country
rock is the Ellsworth schist intruded by a dark igneous rock which is
slightly schistose. The ore consists of thin sheets of quartz, calcite,
rhodochrosite, j^yrite, and chalcopyrite.
CATHERINE HILL MOLYBDENUM MINE.
The Catherine Hill molybdenum mine is at the north end of Tunk
Pond, near the summit of Catherine Hill. The deposit was described
by F. L. Hess « in 1908.
The country rock is a medium-grained granite composed of ]Dink
and white feldspar (orthoclase and albite), quartz, biotite, and mus-
covite. The granite is cut by aplite dikes from one-half inch to 4
inches wide, some of which dip about 15° N. It is cut also by numer-
ous pegmatite veins and veinlets which vary from coarse to fine peg-
matite, the minerals of the latter being only a little larger than the
crystals of the granite. The deposits are worked by open cuts on a
ledge of granite which trends eastward. The principal opening is 75
feet long and 15 feet wide and has a maximum depth of "20 feet. The
pegmatite veins carry quartz, feldspar, molybdenite, apatite, biotite,
chlorite, hornblende, and fiuorite. At some places quartz and feld-
spar are graphically intergrown. Miarolitic cavities are found in
both the granite and the pegmatite, and in the latter are lined with
quartz crystals. The molybdenite occurs as scales and flakes from
one-eighth inch to 1 inch in diameter; some of them are in cracks
which join the pegmatite veins, others in the pegmatite veins them-
selves, and still others in the granite in positions which seem to
have no connection with the pegmatite veins. Most of the molyb-
denite is in or within a few inches of the pegmatite, yet some of it
seems to be an original constituent of the granite. There is little or
no sericitization in the granite that carries molybdenite, and under the
microscope the molybdenite is seen to inclose well-shaped crystals of
albite and orthoclase, the corners of which are slightly rounded, indi-
cating that the potash and soda feldspars were floated in the molyb-
denum sulphide solution and were partly dissolved before it solidi-
fied. The structure is much the same as that shown by some dia-
bases where augite incloses idiomorphic feldspar, except that the
corners of the feldspars in the ore have been rounded by corrasion. A
photomicrograph of this ore is shown in Plate III, B.
"Bull. U. S. Geol. Survey No. 340, 1908, pp. 2.34-235.
U. S. GEOLOGICAL SURVEY
BULLETIN 432 PLATE III
A. POLISHED SURFACE OF SCHISTOSE ORE OF MILAN MINE.
B. PHOTOMICROGRAPH OF MOLYBDENITE ORE FROM CATHERINE HILL.
WASHINGTON COUNTY. 43
WASHINGTON COUNTY.
GENERAL STATEMENT.
The geology of a portion of Washington County has been described
by George Otis Smith and David White." The eastern part of the
county has been mapped by E. S. Bastin and will be described in a
folio of the Geologic Atlas of the United States soon to be
published. The western part of the county is made up in the
main of slates and argillaceous schists. The zinc lode of Cherryfield
is inclosed in these rocks, but so far as known there are no schistose
deposits of pyritic copper ores in Washington County. East of this
area of slates and schists is a broad belt of intruding granite which
extends from JonesjDort to Calais. Some deposits of molybdenite
described by F. L. Hess ^ are associated with pegmatitic phases of the
granite. East of this broad belt of granite, and including Pembroke,
Lubec, and Eastport, is a large area of rhyolite, trap, and other vol-
canic rocks which are in part later than the granite. The Lubec
lead mine, the Denbow Point silver deposit, and the copper deposits
in Pembroke are associated with the basic phases of these volcanic
rocks.
CHERRYFIELD MINE.
The Cherryfield mine, one-half mile east of Cherryfield, was first
opened in 1878 and reopened in 1905. In 1909 it was under water.
G. O. Smith visited the mine in 1907, and the following description
is taken chiefly from his notes. The country rock is a dark aphanitic
diabase, without conspicuous phenocrysts, and is composed of horn-
blende, feldspar, quartz, and magnetite; under the microscope it is
seen to have a well-defined schistosity. Near the mine the dark schist
is cut by unsheared cliorite, and granite outcrops about three-fourths
mile to the northwest. The deposit is a fissure vein which cuts the dia-
base, strikes N. 85° W., and dips steeply northward. A two-compart-
ment shaft is sunk on the lode to a depth of 260 feet, and three short
drifts are turned from this shaft. The vein is from 12 to 20 inches
wide, is banded, and contains fragments of the country rock. The
minerals are quartz, calcite, zinc blende, galena, pyrite, and chalcopy-
rite, and the ore is said to carry silver values. Chlorite is developed in
the wall rock near the lode, but sericite is not conspicuous. No schis-
tose ore was noted on the dump. A mill, erected in 1907, is equipped
with crusher, rolls, trommel, jigs, and concentrating table. A high
percentage of the selected ore is zinc blende.
<■ Geology of the Perry Basin : Prof. Paper U. S. Geol. Survey No. 35, 1905.
" Bull. U. S. Geol. Survey No. 340, 1908, pp. 231-234.
44
SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
LUBEC LEAD MINE.
The Lubec mine is located about 7 miles by wagon road from Lubec,
on a shore marked by high, steep cliffs along which the veins outcrop.
According to report the deposit avp.s discovered in 1828 and has been
worked in a small way through several short periods. A mill, now in
ruins, is said to have been in operation for about six years in the late
sixties and early seventies. A report on the mine by N. S. Manross is
included in the report upon the natural history and geology of
Maine for 1861 (p. 299). xVt present the mine is idle and the
deep workings are submerged. A mill built in late years is equipped
50 Feet
FiGORE 13. — Sketch showing position of pi'incipal veins in Lubec lead mine.
with jaw crusher, coarse and fine rolls, screens, jigs, a Wilfley table,
and two Frue vanners. Steam power was used and the milling was
done with salt water.
The country rock is a dense green trap — an altered surface lava.
Near the mill the trap is in faulted contact with a dark fissile shale.
The freshest specimens of the trap contain much secondary calcite,
chlorite, and a little white mica. Near the lode and in the fragments
which the ore includes chlorite appears to be more abundant than else-
where, but sericite is not consjncuously developed.
WASHINGTON COUNTY.
45
The depOvSits are closely spaced intersecting fissure veins, some of
which are shown in figure 13. The ore carries, besides lead and zinc,
some silver, a little copper, and a trace of gold. The minerals are
quartz, calcite, galena, zinc blende, pyrite, chalcopyrite, and limonite
and manganese oxides. At many places the lodes are opened by short
tunnels, deep cuts, and underhand stopes. Below the mill a shaft
is sunk on the principal lode, but in 1909 this was under water.
Above the mill this vein (No. 8), which strikes westward, is well
exposed in the open cut, and considerable ore has been removed. It
is a foot or more wide and carries galena. It consists of a number of
thin, closely spaced, anastomosing fissures, between which are broken
fragments of trap. Some of the stringers of galena play out
as they pass into the country rock. The shaft sunk on this vein is
reported to be 180 feet deep, and drifts are run out 170 feet under
the bay. Vein No. 9 is east of No. 8, strikes N. 50° W., and would
intersect No. 8 below
the bay. Not far from
the shore a 50-foot tun-
nel is driven in this de-
posit. Where exposed
along the cliff the vein
is a breccia zone 10
feet wide, with about
10 per cent of ore and
g a n g u e minerals in
broken country rock.
No. 5 vein, which
strikes a few degrees
east of north, crosses
the other lodes, and for
80 feet along its strike forms a cliff escarpment 30 feet high. Along
its face are thin flakes of sulphide ere. As shown by this vein, both
sets of fractures, which are nearly at right angles to each other, were
formed before mineralization. This is illustrated also in a small
vein (No. 2) of quartz and galena, which strikes northeastward and
ends in a crossing fissure in a small pit northeast of the mine. The
galena and quartz follow the fissure for a few inches, making a large
angle with their former course, as is indicated in figure 14.
There are said to be thirteen veins in all, but some of those exposed
at tide water to the south of the mill are very small.
DENBOW POINT MINE.
On Denbow Point a shaft is sunk in basic tuffs, but has been lost
through caving. The country rock thrown up on the dum^D shows
stringers of ore composed of quartz, zinc blende, galena, and pyrite.
5 Feet
Figure 14. — Sniall vein in Lubec lead mine. Thie vein
is later than the fissure in wliicli it ends.
46
SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIEE.
PKOSPECTS IN PEMBROKE.
On the road from West Pembroke to Ayres Junction, about 2 miles
northwest of West Pembroke^ there are several prospects in diabasic
lavas. The most extensive workings are on the Sinclair farm, where
the Eastern Exploration Company has recently been prospecting.
The workings are all open cuts from 5 to 15 feet deep, and some of
these are extensive. (See fig. 15.) The country rock is vesicular trap
which, except for a little shearing at pit No. 5, shows no meta-
morphism. The ore occurs as veinlets filling fractured zones, as dis-
seminations in vesicular lava, and as amygdaloidal fillings in the lava.
There is some chlo-
ritization, but seri-
citization is not ex-
tensive. The min-
erals present are
sphalerite, chalco-
pyrite, pyrite, ga-
lena, arsenop7/rite,
and bornite, with a
little limonite near
the surface and
some small stains
of malachite. The
gangue is dolomite,
calcite, and quartz,
and at some places
there is a noticeable
amount of cherty
silica. The dolo-
mite, which is the
most abundant min-
eral associated with
the ore, is jjresuma-
bly ferruginous, since it is nearly everywhere stained with a brown
film upon the weathered surface.
At pit No. 5, which is 120 yards northwest of the blacksmith shop,
an excavation about 20 by J:0 feet, sunk to a maximum depth of about
10 feet, has been made on a glaciated surface. The rock here is a
bluish-gray amygdaloid, bleached white near the surface. Bands of
dense gray flows alternate with the vesicular phases, the banding of
the rock striking about southwest. The flows are cut by closely spaced
parallel fractures which are nearly vertical and strike S. 55° W.
There is a little shearing along some of these fissures as if they had
resulted from compressive stresses. The amygdaloids are from one-
300 Feet
Figure 15. — Sketch showing position of pits of Eastern Ex-
ploration Company at Pembroke. By E. S. Bastin.
WASHINGTON COUNTY. 47
eighth to one-half inch in diiimeter, and many are filled with pure
white calcite, others are filled with calcite and quartz, and some of
them are lined with shells of metallic sulphides with ciystalline
quartz inside. Some of the ore is in the sheared fractures and some
is disseminated in the rock near the fractures. Most of the sulphides
appear as small bodies not one-half inch in diameter, but some are in
masses measuring 4 to 5 inches; zinc blende predominates. Fifty
yards northwest of this pit a small cut shows banded comb quartz
with zinc blende and galena.
At pit No. 2 the trap is traversed by small irregular fractures
healed with quartz and sulphides. The relations are shown in fig-
ure 15. At pit No. 4, 200 yards southwest of the blacksmith shop, the
country rock is darker than at pit No. 5 and some is porphyritic, but
it is presumably a part of the same flow. The rock is cut by many
thin stringers of metallic sulphides, galena and chalcopyrite being-
more abundant than at other pits. This pit is 125 feet long and 20
feet wide ; its trend is S. 30° E., and most of the small stringers strike
southwestward across it.
COOPER MINE.
Molybdenum deposits have been opened at Cooper, and the Amer-
ican Molybdenum Company has erected a mill there for treating the
ore. The deposits have been described by George Otis Smith® and
the following notes are abstracted from his report :
The country rock is granite, presumably of late Paleozoic age, and
is cut by pegmatite dikes. In and near the dikes bunches of molyb-
denite crystals 1 to 2 inches in diameter are intimately mixed or inter-
grown with the quartz and feldspar of the pegmatite, w'here they
were deposited by the pegmatite magma. They also occur in flakes
and nests disseminated through the granite mass, especially near
the pegmatite, where they may have consolidated from the granitic
magma or may have been brought in by the pegmatite solutions,
which are regarded as nearly contemporaneous with the granitic
intrusion. The deposits were visited by F. L. Hess,^ wdio reports
that the molybdenite-bearing granite in the American Molybdenum
Company's mine is shown by a trench and crosscut to be at least 300
feet long and 100 feet wide. Mr. Hess also reports that the Calais
Molybdenite Mining Company, whose property joins the American
Molybdenum Companj^'s holdings on the north, has opened up similar
deposits. Molybdenite has also been found near Sand Cove, Tunk
Pond, and in the town of Brunswick, Cumberland County — at both
places in the granite.
"Bull. U. S. Geol. Survey No. 260, 1905, p. 17.
" Molybdenite in Maine, Utah, and California : Bull. U. S. Geol. Survey No. 340, 1908,
p. 231.
48
SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
SOMERSET AND OXEORD COUNTIES.
ROBINSON MINE.
The Robinson mine, in Concord Township, Somerset County, 7
miles southwest of Bingham and about 1^ miles north of Em den
Pond, was discovered by W. S. Robinson in 1898 and has been worked
noAv and then for several years. It is now owned by the Somerset
Mining Company, which has erected a concentrator near the mine.
Section along Wne ji-A
Limestone
faiJit
A
Limestone han^inj^ wai
7S'
\ Quartzite
hanging wall
2-Foot ore. ^ ^ 3-foot or
X
30 Feet
FiGUEB 16. — Plan and cross section of the Robinson mine, near Concord, Somerset County.
This mil] is equipped with a 12-inch Blake crusher, a set of rolls, a
trommel, and three jigs. It employs steam power generated by wood
and has a capacity of 10 tSns daily. A small amount of concentrates
and 8 carloads of ore have been shipped. The property has been idle
since 1907.
SOMERSET AND OXFORD COUNTIES.
49
The country is an area of quartzite, limestone, and shales, which
are somewhat metamorphosed. These rocks are cut by trap dikes
and probably by other intrusives. The quartzite consists of rounded
quartz grains which under the microscope are seen to be rimmed Avith
secondary silica. Between these grains biotite, chlorite, and horn-
blende have developed. As shown in figure 16, the deposit is a
bedding-plane fissure which occupies the axis of an anticlinal fold.
In thickness it varies from 2 to 8 feet and is thickest at the crest of
the anticline, where it has been stoped or quarried out for about GO
feet along the strike of the crest and from 10 to 25 feet across it. At
the southwest end of the open cut a fault strikes N. 50° W. and dips
75° SW. South of this fault the hanging wall of the deposit is sandy
limestone overlain by shale; northeast of the fault it is quartzite.
The fault is clearly older than
the lode, for the lode crosses
it without interruption. (See
fig. 17.) A trap dike 6 inches
wide, encountered on the south-
west end of the cut, is followed
in a tunnel some 15 feet. This
dike rock is a very fresh basalt ;
even its olivines are but slightly
altered, and it is clearly later
than the ore body which it
crosses.
The gangue consists of quartz
and dolomite. The metallic
minerals are pyrite, galena,
zinc blende, chalcopyrite, ar-
senopyrite, pyrrhotite, and a
little bornite. The sulphides are said to carry silver. Much of the
lode is barren white quartz, and the sulphides in the run of mine do
not constitute more than 4 per cent of the mass, though in selected
ore they run higher. The lode near the dike is quartz, with no me-
tallic minerals. Just at the contact it is slightly oxidized and any
metamorphic changes would be obscured, but an inch away it has
sufl'ered no visible change at the contact with the trap.
MOUNT GLINES.
The deposits at Mount Glines, in Oxford County, have been de-
scribed in a paper by George Otis Smith," from which are extracted
the folloAving notes :
At Milton plantation there are quartz veins in a gneissoid granite
which is probably older than the granite quarried on the Maine coast.
The principal lode is a well-defined fissure vein, with a maximum
width of 4^ feet, composed of quartz and wall rock, the latter altered
<• Bull. U. S. Geol. Survey No. 225, 1904, p. 81,
42381°— Bull. 432—10 i
25 Feet
Figure 17. — Vertical section of wall at open
cut, Robinson mine, near Concord, Somerset
County. Faulting is older than ore deposi-
tion, o. Shale ; h, limestone ; c, quartzite ;
d, quartz and ore.
50 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIEE.
to kaolin and sericite. The ore minerals are pyrite and galena, which
occur in bunches and bands up to 4 inches wide. The sulphide ores
cross the structure of the quartz gangue and are presumably of later
origin than the major portion of the quartz. Assays made by the
Mount Glines Gold and Silver Mining Company are said to give good
value in silver, copper, and lead, but these are presumably of picked
specimens. A sample taken from the upper joortion of the 35-foot
shaft, where the vein is 2| feet wide, and assayed by Dr. E. T. Allen,
yielded less than $1 in combined metals.
MILAN MINE, NEW HAMPSHIRE.
GENERAL STATEMENT.
The Milan mine is in Coos County, northern New Hampshire, in
the foothills of the Presidential Range, about 8 miles northwest of
Berlin and one-fourth mile from the Grand Trunk Railway at
Marston, with which it is connected by tramway. The deposit was
discovered in the seventies and was worked steadily until 1886.
According to Herbert J. Davis," the monthly production was 2,600
tons, and this production was presumably sustained for several years.
A 60-ton smelter was installed at the mine, but the fumes killed the
spruce, and, owing to objections of the farmers and the decline in the
price of copper, this was closed after a small tonnage had been -put
through. The jDroperty was opened again in 1895, when lessees
mined about 1,500 tons of ore. It was acquired in 1907 by J. B,
Carper, of Portland, who organized the Milan Mining and Milling
Company, which is now working the mine and making regular ship-
ments of ore and concentrates.
The deposit, first worked by open cuts, is operated through a
265-foot shaft inclined from 59° to 85° W. Levels are turned 70,
88, 115, and 215 feet (measured on the incline) below the collar; these
aggregate about 1,500 feet.
The character of the deposit and its situation and accessibility to
markets for all the products favor low costs both for mining and
for milling. The stojoes are at many jDlaces from 10 to 20 feet wide
and the rock breaks well and runs easily in the chutes. Practically
no timbering is required to hold the ground even when the large
stopes are left open. The concentration of the ore is satisfactory
for the pyrite, but the saving of copper, gold, and silver is low, and
where these exceed a certain value it is found to be more profitable
to ship the rock than to mill it. The ore is mined with air drills,
dumped in a chute, and loaded in buckets of 1,200-pound capacity.
It is hoisted to the top of the mill, where it falls over a grizzly, the
fines going to a 1-inch shaking screen, from which they go over an
elevator to the rolls. The coarse rock from this screen and from
the grizzly passes over two picking belts on which the ore is washed
"Mineral Ucsoui-ces U. S. for 1885, U. S. Geol. Survey, 1886, p. 501.
MILAN MINE, NEW ITAMPSIIIEE.
51
by a small stream of water to facilitate cobbing. The waste from the
picking- belt is sent to the clump, the low-grade pyrite ore is run
through the mill, and the ore carrying a noticeable amount of copper
is shipped to smelters. The milling ore goes through a Dodge crusher
and is elevated to the
Grizzly
ore bin, from which it
passes through coarse
rolls, up an elevator
through an impact
screen of one-eighth
inch mesh. From this
screen the fines go to
a thickening tank and
pass to a Richards pul-
sator classifier, where
they are classified for
the two Wilfley and
three Bartlett tables.
The coarse material
from the screen goes
through fine crushing
rolls and is elevated
back to the shaking
screen. The mill feed
carries about 26.5 per
cent sulphur and 1.35
per cent copper. The
concentration is 2 or
Fine
I
1-inch screen
Coarse
f
Picking belt
Fine
Coarse
I
Picking belt
Shipping ore
Waste
Shipping
ore
Milling ore
Dodge crusher
1
Elevator
I
Bin
t
Coarse rolls
Elevator
Undersize
Thickening tank
t
Richards pulsating classifier
2 Wilfley and 3 Bartlett tables
Impact screen Vs in.
— ' ^ f .
Oversize
Fine rolls
i
Concentrate to
bins
to sluice
FiGDEH 18. — Plan of ore treatment at Milan mine,
New Hampshire.
3 to 1 and the concentrates are shipped to acid works, from which
the cinders are sold to smelters and smelted for the copper, gold,
and silver. Analyses of representative concentrates and cobbed ores
are given below :
Analysis of concentrates from Milan mine.
[Chas. L. Constant, analyst.]
Ounces per ton.
Gold 0. 21,
Silver 1. 50
Per cent.
Copper 1. 58
Arsenic None.
Sulphur 41.30
Silica 12. 47
Alumina 2.80
Iron 35.00
Lime Trace.
Magnesia 0.30
Zinc 6.46
52 SOME OKE DEPOSITS IN MAINE AND "NEW HAMPSHIEE.
Analysis of shipping ore cothed from the mine run.
Per cent.
Insoluble- 15.40
Sulphur 39. 84
Copper 2. 25
Zinc ^ 7.26
Lead 1.57
Iron 32.85
The ore carries about $1.50 in gold and 1 or 2 ounces in silver to the
ton, and the sulphur, iron, copper, gold, and silver yield from $12 to
$18 a ton. There is a considerable accumulation of tailings from for-
mer operations which carry 36 per cent of sulphur and 1 per cent of
copper, and these are now being put through the mill for their pyrite
content. From the low copper content of the concentrates it appears
that a high percentage of the copper passes off in the slimes.
GEOLOGY.
The Milan area is included in the great shield of crystalline schists
which covers most of New England and which is generally regarded
as of pre-Cambrian age. These schists have been intruded presum-
ably in Paleozoic time by great masses of granitic rocks which show
little or no deformation by shearing and are therefore later than the
regional metamorphism of the schists. To the east and south these
rocks cover extensive areas, but they are not known to be present
in the vicinity of the mine.
The geology of New Hampshire has been mapped and the rocks
described by C. H. Hitchcock.'^ In the geologic atlas accompanying
his report the rocks inclosing the copper deposits are mapped as the
Lyman group, a belt of which 3 or 4 miles wide extends from a point
2 miles south of the Milan mine northward toward the Canadian
boundary. A belt of the same rocks separated from the first by
intruding j)orphyry extends southwestward 50 miles or more beyond
Woodville. The latter belt includes the mines of the Ammonoosuc
district, which have been worked for copper, gold, and silver. The
deposits of these mines, to judge from the descriptions of the ores,
have many features in common with the deposits at Milan.
The rocks mapped by Hitchcock as the Lyman group are mainly
quartzites and siliceous chloritic schists, which were regarded by him
as upper Huronian. They are in the main siliceous sedimentary
rocks intensely metamorphosed. On either side of this belt are areas
equally long and wider, which Hitchcock mapped as the Lisbon
group. These two groups of rocks are intimately interfolded and
" Geology of New Hampsbire, vols. 1 to 3.
MILAN MINE, NEW HAMPSHIRE. 53
presumabh^ have about the same age and origin. Southeast of the
Milan mine, including the area of the Milan Hills and extending
southward beyond Berlin, is an area mapped by Hitchcock as " Lake
and Granitic gneiss." The contact relations with the Huronian rocks
are not given, but this gneiss is presumably in part a regionally
metamorphosed granite, the age of which is not known.
The top of the Huronian series is the auriferous conglomerate which
is exposed at many places in New Hampshire. It contains pebbles
of jasper, schists, and quartz and has been greatly metamorphosed.
It carries locally from 40 cents to $2 a ton in gold, but it is not clear
whether the gold is a clastic constituent or was introduced after the
formation was deposited; the presence of quartz pebbles, how-
ever, suggests the possibility of mineralization prior to regional
metamorphism.
The country rock at the mine is a highly metamorphosed siliceous
schist. In the underground workings, which do not go far into the
country rock, it shows neither quartzites, limestones, or conglomerate
layers, nor grains of grit, bedding planes, or other characteristics of
sedimentary rocks that would indicate its clastic character. It has
well-defined planes of schistosity, which near the mine strike north-
ward and dip from 30° W. to 90°. Locally they dip eastward at
very high angles. The microscope shows the schist to be composed
of quartz, chlorite, biotite, muscovite, and pyrite. The quartz grains
are oriented parallel to the mica and chlorite flakes.
On the surface, perhaps one-fourth mile northwest of the mine and
between the mine and the railroad track, beds of highly siliceous schist
outcrop at many places. Some of these rocks contain a myriad of
thin dark actinolite fibers. Where subjected to weathering the
siliceous schist shows the rounded sand grains of a fine quartzite.
The wall rock of the mine is less siliceous than the quartzite and
contains a greater percentage of chlorite, biotite, and muscovite.
Mineralogically the wall rock is such as may have resulted from the
intense regional metamorphism of a quartz-rich shale or clayey
quartzite, and there is nothing inconsistent with a sedimentary origin
in its general appearance and mineralogical composition.
J. W. Huntington,* of the New Hampshire Geological Survey,
describing the area near Milan, says :
The railway cuts the gray siliceous schist in the east part of Stark, in the
corner of Dummer, and at several places for a mile east of West Milan. East-
erly dips prevail on the west and westerly dips prevail on the east, so as a
whole it seems to be a synclinal axis with minor folds near the middle of the
area. The rocks, except the hard siliceous schists on the west, we have placed
in the Lyman group, which is the upper member of the Huronian.
« Hitchcock, C. H., Geology of New Hampshire, vol. 2, 1877, p. 201.
54
SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
From these observations it seems that the Milan mine is on the
east limb of the synclinal axis formed by the schistosity. A cross
section taken from the New Hampshire atlas is shown as figure 19.
On the 115-foot level of the mine, about 35 feet northwest of the
shaft, there is about 3 feet of an actinolitic schist which is different
in appearance and mineralogical composition from the biotite schist
that constitutes the walls at most places. It consists of a dark,
fine-grained groundmass containing abundant crj^stals of hornblende
about 1 mm. thick and 1 cm. long. Under the microscope the horn-
, Stark
Porphyry rPercyPd..
corpnyry
I
Androscoggin, R.
Lisbon I
group
Lyman group
/ / Lake gneiss \ Lisbon group
OvicKwolnepy Str.
FiGUEB 19. — Geologic east-west cross section through West Milan, N. H., north of the
Milan copper mine. (After Hitchcock, Atlas of New Hampshire, 1878.)
blende shows characteristic cleavage and is surrounded by a ground -
mass of fine quartz and clouded sericitic bodies, which are probably
decomposed feldspars. It contains also some chlorite, magnetite, and
calcite. This rock appears to be more basic than the biotite schist
and, to judge from its relations with the schist, it is probably the
metamorphosed product of a dike of diabasic or more acidic compo-
sition— a dike which cut the siliceous country rock before that rock
was metamorphosed.
MINERALS OF THE ORE.
The deposits are overlapping pyritic lenses parallel to the schis-
tosity of the country rock. The gangue is quartz, chlorite, black
mica, and white mica. The sulphides are pyrite, chalcopyrite, zinc
blende, galena, bor-
nite, and chalcocite.
Little or no mag-
netite is present and
pyrrhotite was not
noted in several tests
that were made. In
a list of minerals of
New Hampshire,
published in 1886,*^
however, it is men-
tioned as occurring
in the ore. The ore carries $1.50 in gold and about 1 ounce of
silver to the ton. Much of the ore is solid pyrite, which includes
fragments of the banded schists oriented parallel to the walls.
Here and there the pyrite is cut by white quartz stringers, as is
Figure 20. — Pyrite cut by quartz, Milan mine.
6, pyrite.
a. Quartz ;
» Mineral Resources U. S, for 1885, U. S. Geol. Survey, 1886, p, 757.
MILAN MINE, NEW II AM PS 1 1 IKE.
DO
shown in figure 20. Some of the sulphide ore, notiibly in the
crosscut to the west at the south end of the 115-foot level, is massive
zinc blende, carrying well-formed crystals of pyrite 1 mm. in diame-
ter, with here and there small specks of galena. In the stope at the
north end of the 115-foot level and between the 115-foot level and the
70-foot level above the main ore body, a mass of white quartz is cut
by veinlets of galena and pj^rite and has specks of those minerals
scattered through it. Below this ore the vein consists of i:)yrite and
chalcopyrite cut by innumerable fracture planes which are filled
with paper-thin films of chalcocite, the whole carrying 12 per cent of
copper. An oxidized seam with C inches of limonitic material is
above this body of copper ore, and this appears to have been a water-
course which was followed by the downward circulation of sulphate
waters which deposited chalcocite and bornite films on the chalcopy-
rite. This ore, Mdiich carries more of the primary chalcopyrite than
the mine run, is also richer in gold. Some of it carries as much as
one-fourth ounce to the ton. A cross section of the vein at this place
sw
10 Feet
Figure 21. — Section of vein at east end of 115-foot level, 40 feet above floor, Milan mine.
a, Oxidized streak ; h, schist ; c, massive quartz, pyrite. and galena ; d, pyritiferous schist
or milling ore ; e, massive pyrite.
is shown in figure 21. The lode is at no place completely oxidized,
but in the slopes 40 feet below the surface limonite in seams and
copper carbonate and sulphate were noted at many places along nar-
row fractures. Locally the sulphide ore extends to the grass roots,
with only a light veneer a fraction of an inch thick where it is
exposed to the air.
ORE BODIES.
The ore bodies are two overlapping lenses separated by 10 or 15
feet of biotite schist. They strike a few degrees east of north and
dip steeply westward. They are not tabular but broadly they ap-
proach that form. In detail, however, they are characterized by gen-
tle undulations along both the dip and the strike and at some places
56
SOME OKE DEPOSITS IIST MAINE AND NEW HAMPSHIRE.
there are turns of more than 45° along both dip and strike. The south
ore body outcropped on the present site of the mill and the mine was
first worked in an open cut from 15 to 25 feet wide, which extends
200 feet along the strike. At a depth of 70 feet a shaft was sunk
and stopes in both ore bodies were carried wp to that level. The
south ore body as developed is from 5 to 25 feet wide and like the
north ore body it dips steeply westward. Near the surface it is
developed southward for 275 feet along the strike. At its northern
termination the end of the ore pitches southward at a low angle.
On the 70-foot level it is 45
feet from the shaft and dips
toward it from 50° to 70°,
becoming steeper in depth.
Near the end of this lens,
at the pump station below
the 115-foot level, the ore is
highly crumpled.
The north ore body is de-
veloped northward 550 feet
along the strike and it is
approximately 15 feet wide.
The south end of the north
ore body on the 115-foot
level is encountered in a
short crosscut, 40 feet
southwest of the shaft. It
has been followed N. 20°
E. for a distance of 360
feet, where it bends to due
north, keeping the course
for 120 feet. At chute No.
2 it turns at an angle of
? . , , , 50 Feet. 40°^ striking N. 40° E. for
Figure 22. — Cross section of ore bodies, Milan mine. ^5 feet. A crOSS SCction of
the two ore bodies 35 feet south of the shaft is shown in figure 22,
and a plan of the 115-foot level in figure 23.
From a point near the east end of the 115-foot level and about 40
feet up in the slope the section of the lode, which here dips 40° NW.,
shows 4 feet of massive pyrite above a foot wall of chloritic quartz
schist. Above this is 6 feet of pyrite and quartz with a little mica, all
highly schistose, the planes following the orientation of the lode.
Above the latter is a mass of quartz about 3 feet thick, with seams of
pyrite and galena. Near the' center of the 6 feet of pyrite and quartz
which constitute a milling ore there is a seam of highly oxidized ore
MILAN MINE, NEW nAMPSHIRE.
57
along a plane of movement. This plane is clearly a postmineral
fissure. A few feet lower this
fissure departs from the ore body,
keeping- its regular course while the
ore body turns, striking nearly
northeastward and dipping steeply.
Where noted in a drift below it is
vertical and at one place overturned.
The ore bodies are parallel to the
schistosity. At some places the
walls are intensely crumpled and
much of the milling ore consists of
the thin alternating bands of schist
and pyrite intimately interbanded
and crenulated. These seams of py-
rite and quartz are also parallel to
the schistosit}^, and as shown by S
Plate III, A, are clearlj^ metamor- §
phosed by the same crumpling move- li
ments. The ore is undoubtedly J^
older than the metamorphism of the g
schists. At many places it grades a
into the pure massive pyrite ore, but m
the latter does not show any schis- g"
tosity. There is no noticeable seri- ^
citization or other hydrothermal |
metamorphism of the walls nor any "^
leaching of the wall rock, such as is ^
characteristic of most ore bodies not g
regionally metamorphosed, and the g
ore at no place shows comb struc-
ture, crust ification, or druses.
The i^tan of the 115-foot level
illustrates further the eifects on the
ore body of the regional metamor-
phism due to intense shearing move-
ments under load which develoj) the
schistose structure in the country
rock. Before shearing the ore body
was probably a single tabular mass,
but by these movements it was
thrust endwise upon itself, so that
it divided and overlapped. The di-
vision can hardly be called a fault
in the common sense, since it took
place in the zone of flow for the schist and was a pulling apart, not
w
'ill
Mm
58 SOME OEE DEPOSITS IN MAINE AND NEW HAMPSHIRE.
by a sharp cleavage, but rather as a somewhat viscous body is divided.
A tight fissure dipping westward at about the same angle as the two
ore bodies joins the two ends and wraps around the ore at both termi-
nations. The schistosity likewise wraps around the ends of these ore
bodies and parallels the fissure which joins them. These features are
shown in figure 23. This relationship of the schistosity to the line of
movement which separates the two lenses shows that the ore body has
been subjected to the same earth movements as the rock. Since it has
separated in the zone of flow it must have been deposited before regional
metamorphism. This is further indicated by the gradation of the mas-
sive i^yrite ore into pyrite containing parallel quartz and mica bands,
of this into quartz biotite with numerous thin bands of pyrite, and of
this, again, into schist with only an occasional band of pyrite and this
into nearly pure schist. Thus the rock shows bands of the schist and
bands of the pyrite varying in all proportions along the wall, and
the ore always shows the minutely schistose structure wherever it
contains quartz and biotite. The main lode of pyrite ore has ex-
actly the same character as the smaller massive layers and must
have the same origin, but where pure and large it is as free from
conspicuous marks denoting movement as any ore deposit in un-
metamorphosed rock. Some of the crystals of pyrite have perfect
form when included as the thinnest seams . between the quartz-rich
or biotite-rich layers of the schist. As these pyrite seams increase in
size and purity they become more massive, and where silica minerals
are absent the ore does not show any lamination parallel to the schis-
tosity of the country rock, although the ore is, without doubt, older
than the final metamorphism of the schist and partook in its move-
ments. The aluminous, more or less plastic wall rock was capa-
ble of crumpling to gnarly schistose layers, and where the seams
of pyrite alternate with thin seams of quartz the same schistosity
is shown; but massive pyrite ore not containing quartz or clayey
material adjusts itself to conditions of pressure without leaving a
conspicuous record of the movements. The pure pyrite is at no place
laminated. The larger pyrite bodies have broken and have been re-
cemented by pyrite and the smaller crystals have completely recrystal-
lized, mainly into small cubic and octahedral crystals rather than into
l^yritohedrons.
Galena and zinc blende have also recrystallized. Some of the chal-
copyrite shows faint lamination, a feature of chalcopyrite noted also
in the Tapley mine at Brooksville, Me.
The ore bodies are believed to be tabular deposits of sulphide ore
metamorphosed by the same movements that converted the highly
quartzose shales into quartz-biotite schists. It is remarkable that
this lode, like most of the members of the class, should every-
where be approximately parallel with the schistosity of the country
MILAN MINE, NEW IIAMPSHIKE. 59
rock. Ore bodies in a given district of unnietainorphic rocks very
often present a great variety of dips ;uid strikes, and in many districts
there are two vein systems nearly at right angles to each other. The
movement causing the schistosity is apparently controlled to some
extent by the ore bodies or else the ore bodies are rotated to conform
to the general movements as recorded in the structure of the schists.
Probably the agreement of ore with schistosity is brought about in
both Avays. First, the pyrite bodies are broken and the parts tend
to orient themselves at right angles to the line of pressure, as, for
example, the flat or oblong grains of sand in a quartzite or quartz
schist, or as the mica flake in a mica schist ; and, second, the schistos-
ity of the walls is probably controlled locally by the large masses
of ore if the ore body is too immobile to orient itself to conform with
new conditions of pressure as do the oblong quartz particles in the
quartzose shale when it is metamorphosed to biotite schist.
At the south end of the north ore body on the 115-foot level the ore
is highly siliceous and consists of intensely crumpled pyrite and
quartz. At this place, where the ore body pulled apart and became
two lenses, the ore looks like a surface of gnarled oak or vermicelli.
Here the schistosity of the walls instead of striking northward
parallel to the main lode strikes westward parallel to the end of the
lens. On an intermediate level, just below, near the pump station,
the same intense crumpling is shown at the north end of the south
ore body.
These places show that the ore body broke where it was most
siliceous and most heterogeneous and because of that hetero-
geneity of composition the movement was best recorded. If it had
been pure pryite instead of quartz-pyrite-chlorite ore it would not
have shown the intense crumpling, foi the pyrite would have broken
and recemented into an apparently homogeneous mass. Since the
broken end of the south ore body pitches toward the south, with the
ore on the foot wall of the pitch, it should be expected that the broken
end of the north ore body should also pitch to the south, with the
ore on the hanging wall of the pitch.
SUMMARY OF THE GENESIS.
The deposit was at one time a large mass of ore contained in impure
quartzite or slate which if metamorphosed was less intensely metamor-
phosed than at the present time. The ore may have been deposited at
the time the granular rocks mapped by Hitchcock as " Lake and Gra-
nitic gneiss " were erupted or at the time of the intrusion of a basic
igneous rock which is now actinolite schist. It was not, however, a
contact-metamorphic deposit, for it has none of the characteristics of
such deposits and it does not contain garnet and epidote and other
lime silicates which are usually found in such deposits. Presumably
60 SOME ORE DEPOSITS IN MAINE AND NEW HAMPSHIBE.
it was first formed at moderate depth and then consisted of quartz,
pyrite, zinc blende, galena, chalcopyrite, and some aluminous mate-
rial— either clay or sericite; the walls were presumably replaced by
pyrite and other minerals. After deposition it was deeply buried
and was intensely deformed in the zone of flow at the time when
the siliceous shales were subjected to regional metamorphism and
changed to schists, or at the latest before this process had ceased to
operate. During the process of metamorphism the deposit was de-
formed by pressure. Certainly it was pulled apart at one place and
thrust back on itself so that the two ends overlapped some 40 feet.
The ore body pulled apart where it was most siliceous, where parallel
sheets of quartz and mica are abundant in the pyrite, and because
of this circumstance of heterogeneity also a maximum of squeezing
and crumpling was recorded. The sulphides were crushed, re-
cemented,* and at some places dissolved and reprecipitated. Drusy cav-
ities and banded and comb structures, if present, were destroyed. Any
evidences of hydrothermal metamorphism along the walls of the
deposit were obscured by the subsequent regional metamorphism of
the deposit and the country rock. After metamorphism the rock
above the deposit, probably a considerable thickness, was eroded
away, and minor movements resulted in fractures and slickensided
planes, cutting the lode approximately parallel to the dip and strike.
Ultimately through water and glacial erosion the present outcrop of
the deposit was exposed. Descending sulphate waters deposited a
little chalcocite in the later fractures. The lode was partly oxidized
at the outcrop, but at most places the oxides did not extend more than
40 feet below the surface and at some places near the surface they
scarcely formed at all.
INDEX.
Page.
Acknowledgments to those aiding 8
Amos Knob formation, occurrence and char-
acter of 12-13
Bastin, E. S.,aidof 8,11
Battie quartzite, occurrence and character of. 12
Bibliography 8-10
Blue Hill mine, description of 33
ores of 16, 19, 33
vicinity of, geologic map of 30
Brookville, copper near 16
Cape Rozier mine, description of 38
ores of - 19, 38
Castine formation, occurrence and character
of 13
ores in 15-16
Catherine Hill mine, description of 42
ores of 21,42
figure showing 42
Cherryfield mine, description of 43
Coast, outcrops on 25
Concord mine, ores of 21
Cooper mine, ores of 47
Copper ores, age of 15
deposits of 16-19, 22
mining of 11, 16, 27, 31-32, 34-38, 41, 46-47
production of 11
Copperopolis mine, description of 41-42
Deer Isle mine, description of 37-38
ores of 19, 20, 27, 38
figures showing 20
Denbow Point mine, description of 45
ores in 22, 45
Diabase, ores associated with 22
Dikes, occurrence and character of 15
Diorite, occurrence and character of 15
Douglas mine, description of 31-32
development at 11
ores in 26
analysis of 32
Eggemoggin mine, description of 36-37
Ellsworth schist, occurrence and character
of 11-12
ores in 15-16
Emerson mine, description of 39
ores of 19, 39
Enrichment, secondary, eflects of 26
Field work, extent of 8
Fissure veins, occurrence and character of . . . 20-21
Franklin Extension mine, description of 41
Geography, character of 10
Geology, outline of 11-15
See also particular counties.
Glaciation, effects of 24-25
Gouldsborough mine, description of 40-41
ores of 21,41
Granger mine, description of 35
Granite, occurrence and character of 14-15
ore deposits associated with 20-22
Hancock County, geology of 30-31
mines in, description of 31-42
Hercules mine, description of 38
ores of - 19,38
Hess, F. L., on Cooper mine 47
Hitchock, C. H., on Milan mine 62-53
Huntington, J. W., on Milan region 53
Iron, mining of 7, 10
Islesboro formation, occurrence and charac-
ter of 12
Jackson, C. T., cited 10
Jewel Island, mining on 10
Jones & Dodge mine, description of 38
Kempton, C. W., on Sullivan mine 40
Lava, occurrence and character of 15
Lead ores, age of 15
deposits of 21-22
mining of 10, 2&-27, 32-35, 37, 41, 43-45
Lindgren, Waldemar, aid of 8
Literature, list of 8-10
Lubec, lead at 10
Lubec mine, description of 44-45
ores in 22, 44-45
figures showing 44, 45
Maine, southern, map of 7
mines in, descriptions of 30-50
Mammoth mine, description of 34
Map of southern Maine 7
Metals, occurrence of 7
production of 11
Metamorphism, effects of 18-20
occurrence and character of 28
time of, relation of ore deposits and 15
Milan mine. New Hampshire, description of. . 8, 50
faulting in 29, 50
genesis of 59-60
geology of 50, 52-54
minerals in 54r-55
ores of 16-17, 26, 50-52, 55-59
analysis of 51, 52
figures showing 17, 19, 42, 54, 55, 56
plan of, figure showing 57
section near, figure showing 54
Mineralogy, data of 22-24
Mines, description of 30-60
future of 26-27
61
62
INDEX.
Page
Mining development, extent of 10-11
Molybdenite, mine of 42, 47-49
occurrence and character of 21
plate showing 42
Mount Glines, description of 49-50
Mount Katahdin, iron on 10
North Haven greenstone, occurrence and
character of 13-14
Ore deposits, age of, relation of, to metamor-
phism 15
classification of 15-22
distribution and character of 15-18
figures showing 17, 18, 19, 20, 21, 22
geologic history of 27-30
metamorphism of 18-20
mineralogy of 22-24
origin of 20
outcrops of 24-25
oxidation of 25-26
Sec also Metals; Mines.
Outcrops, distribution of 24-25
Owen lead prospect, description of 34-35
ores of, figure showing 20
Owen mine, description of 34
ores of 21, 34
Oxford County, deposits at 49-50
Oxidation, effects of 25-26
Pembroke, ores of 22, 46-47
ores of, figures showing 22, 46
Penobscot formation, occurrence and char-
acter of 12
Perry formation, occurrence and character
of 13
Pine Tree mine, location of 39
Production of metals, data on 11
Page.
Pyrite, mining of lo
Robinson, F. C, aid of 8
Robinson mine, description of 48-49
ore of 49
figure showing 49
plan of, figure showing 48
Seacoast, outcrops on 25
Silver ores, age of 15
deposits of 19-20, 22
mining of 11, 26-27, 36-37, 39-41, 43, 45
production of 11
Smith, G. O., aid of ; 8, 11
Somerset County, mines of, description of 48-49
Stewart mine, description of 33-34
Stone, quarrying of IQ
Sullivan mine, description of 39-40
ores in 20-21, 40
figures showing 21-39
Tapley mine, description of , 35-36
ores at 16,36
figure showing 16
Thorofare andesite, occurrence and character
of 14
Twin Lead mine, description of 32-33
ores in 16, 33
figures showing 17, 18
Vinalhaven rhyolite, occurrence and char-
acter of 14
Washington County, geology of 43
mines in, descriptions of 43-48
Waukeag mine, description of 39
Weil Freddie mine, description of 35
Zinc ores, age of 15
deposits of 19, 20, 21
mines of 26-27, 34-39, 41, 43
o
DATE DUE
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