The Virginia enterprise. [volume] (Virginia, St. Louis County, Minn.) 1893-19??, 1905-07-14
MOLYBDENITE. NINE.
ORE USED IN MANUFACTURES OF
STEEL FOUND IN MAINE.
Deposits Are of Rare Occurrence and
the Value Of Those Located
Is Partly Conjec-
tural.


Smith, of the United States geologlcal
survey, who tells in bulletin 260, the
surveys annual publication on It's ex-
ploits in economic geology, how the
American Molybdenum company pre-
vented him from having more to say
about the molybdenum of this locality.
He was not permitted to visit the mine,
but the observations he made at the
surface furnished him sufficient data
for a consideration of the character and
origin of the deposit.
The town of Cooper is in Washing
ton county, in the extreme southeastern
part of Maine, and is the fourth town.
ship west of Calais. The nearest rail-
road station is Marion, in the second
township south. Prospecting for mo-
lybdenite has been carried on at sew
eral points in this locality, but the only
important development thus far is that
on the property of the American Mo-
lybdenum company.
The molybdenite occurs both in peg
Matte dykes and in the granite cut by
these dykes. A number of distinct peg
Matte dykes were seen on this property,
varying in width from few inches to
several feet. In these the molybdenite
occurs in lead-gray hexagonal crystals
Of short prismatic habit, or as less reg
ular foliated masses, often with radiate
structure. The molybdenite is found
also in small flakes or larger nests of
flakes disseminated throughout the
granite mass.
Molybdenite occurs at several other
localities in Maine, as well as in the
other New England states. 1t is usu-
ally found in small fakes disseminated
through the granite or gneiss, so that
the Cooper occurrence is Of special
interest by reason of the light 1t
throws on the origin of this mineral.
The pegmatite dykes are probably
approximately contemporaneous with
the granite intrusion, representing
the latest disqualification of the gran
itic magma, and therefore intruding
the consolidated granite. In this
pegmatite magma molybdenum disul-
phide appears to have been a promi-
nent constituent and to have crystal
lized early in the consolidation of the
dykes. The molybdenite in the gran
lite may be either the result of impreg-
nation at the time of the pegmatitic
intrusion or it may be an original con-
stituent. The former view is support
ed by the apparently larger amount in
the granite near the dykes.
The ores of molybdenum have been
in greater demand since molybdenum
has been used in the manufacture of
steel to increase it's hardness and
toughness. The comparative rarity and
high cost of the ores, have, however,
limited it's use.
The economic value Of such deposit
as the Cooper molybdenite spartly con-
jectural. The conditions for quarrying
and mining both the pegmatite and the
wall rock appear favorable, and con-
siderable work Of this kind has been
done. The rock lying on the dump
contained varying proportions of mo-
lybdenite, but it seemed that most of
the crude ore could be readily distin-
guished and separated from the barren
rock by hand picking. The crucial test
of the successful working of such de-
post is doubtless connected with the
milling process, rather than with the
mining methods. A compact plant for
treating the molybdenite ore has been
erected by this company, but the de-
tails as to cost of crushing the rock and
OF concentrating and cleansing the sep
arated mineral could not be ascertained.