The Arizona copper camp., 1920-03-13
SECRETS OF THE ROCKS
tBy E. B. Young, Geological Depart
mantl

Noy y. B. Young, Geological Depart
ment)
The Onaconda Hill is famous the
world over for its wonderful mineral
deposits. The valuable minerals are
found here ir variety and quantity
that is truly remarkable and unique
And because of this variety and i'm
portance it has been thought desir-
able to devote one article in this
serie to a rcmfwy cmfwy vbgkq cmfw
series to a few comments on Butte
minerals.
When Butte's mineral industry is
mentioned one thinks of copper. The
S0O,O0O,000 pounds produced annually
go long way in supplying the needs
of our nation. However, the stranger
looking at the long ore trains filled
with their piles of gray rock would
wonder not little. The famous
mines of Michigan produce native
copper, but not so here. The copper
of the Butte veins was very skillfully
camouflaged. Sometimes it is a sooty
block deposit; sometimes a yellowish
mineral; again it is a banded min
eral of indigo blue, or sparkling
mixture of blue and green, or even a
glistening black mass which emits the
smell of the garlic when heated To
be sure, native copper has been found
in the Tropic mine and in small
amounts elsewhere, but these occur
rences are the exception and not the
rule.
Let us take up these various copper
minerals briefly. The black SCOT is
one form of copper glance 1t is near
ly 80 per cent "copper". the remaining
being sulphur, and is found in the up
per levels of many of the mines,
where it made possible the bonanzas
of the early days. However, copper
glance, as the miner sees it today, is
usually small patch of mineral, lead
gray, but soon furnishing to dull
black, and easily cut wit ha knife. 1t
is very widely scattered throughout
the copper zone of the district and to-
gether with the sooty variety has pro-
.duced perhaps so per cent of the total
copper.
The mineral responsible for the gar
lie odor is enargite. 1t is scarcely
half copper, for arsenic and sulphur
make up So per cent of the substance.
The arsenic is the cause of the odor.
Beautiful crystals are sometimes
found and even in the massive varie-
ties the cleavage faces give glisten
to the mineral. It is grayish-black
and easily cut with knife. 1t is
widely distributed but is found espe-
cially in the Leonard, West Colusa,
Pennsylvania and in the deep levels
of the Steward and Original AL
though comparatively rare mineral
and found in but few districts, it has
produced perhaps 80 per cent of the
Butte copper.
1t is also the principal source of the
arsenic which is produced id large
quantities at the smelters, at Ana
conda and Great Falls. Hundreds of
tons of this material are used every
year as an insecticide; as a weed
killer, as sprays, dips, and in medi-
cine. When used in glass making, it
imparts a clear crystal luster to the
glass. Its uses as hardener of lead
and as an ingredient of some of the
poison gases were of great Importance
during the war.
The beautifully bladed mineral Of
indigo blue is covellite. 1t is two
thirds copper and one-third sulphur.
When moistened on the tongue it be-
comes brilliant purple. 1t is a rare
mineral, much softer than enargite
and easily identified 1t was found
abundantly in the upper levels of the
Gray Rock and Edith May veins and
in the Leonard from the 1900 to the
1000 level.
Bornite, named after the mineralo-
gist Won Born, who died in 1891, is
one of the most common of the cop
per minerals. 1t is our old friend