The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-10-16


In the case Of the ore making solu-
tons 1t Is not so easy to get around
this difficulty. The solutions appear
to have started In the Prichard for-
parativeIy rich in zinc. For time
they lost zinc faster than lead. Be
cause of its stronger affinity for sui
phur and less solubilty, lead sui
phide should have been precipitated
first and should be more abundant at
lower levels. If the meteorological
character of the Prichard type be at
tribuated solely to the precipitating
effect of the slaty rock, the carbon
marks the only important mineral
oGical difference between this rock
and the higher rocks and this carbon
should have made galena more abun =
dant at lower levels than higher. My
impression Is that the explanation
will lie along the lines that the min
erals in the Occur d'Alene were car
red as sulphides dissolved in hot
water under pressure and precipitat-
ed by decrease of heat and pressure.
l have not been able to find any
chemical law which will permit zinc
sulphide to be precipitated In pref
erence to lead sulphide, nor have I
found any very definite statement as
to the behavior of dissolved sulphides
under considerable heat and pressure.
Copper and Gold Minerals.
L. there are any mineral deposit;
in the Occur dAlene district that de-
rive their metals from the nonzonite
magma, they are more likely to be
the copper and gold than the lead AMI
zinc deposits, In central Idaho where
erosion has cut deep into the quartz
monzonite batholith, some idea If
what minerals may be traced to the
deep seated portions of the batho-
18th may be obtained The geologic
map Of North America shows broad
expanse of post -Cambran intrusives
In central Idaho, A large part of
this area Is quartz nlonzonite Turn
ing to plate VII in bulletin 5o7, U. s.
geological survey, it will be found
that this area is studded with dis
tricts in which gold is predominant
a few with silver predominant, and
none with lead predominant. From
this it seems proper to infer that COLA
would be, by value, an important
constituent of any mineral deposit
derived from the deep-seated por-
lions of the batholith The silver
lead deposits of the Wood river re-
gion near HALEY in Blaine county,
Idaho, are cited as supporting the
magmatic origin of the Occur d'Alene
deposits, because they occur in sedi-
ments on the TANKS of the great CEN
trail Idaho granite area, because
these sediments are intruded by the
granite. or quartz monzonite masses,
because sderite is abundant, and be-
cause of metasomatism in the ore de-
posits and its weakness in the coun-
try rock. l have not seen the Wood
river deposits. but l see nothing III
the description that precludes the
that the lead was deriv-
ed from the sediments.
The copper deposits at Butte Mon"
tana. occur in the Bouldey bathollth
of quartz monzonite. similar bath
oliths of granite occur elsewhere IN
the Montana ranges and are probab-
ly connected with deep-seated par
ent mass that underlies the entire
region between the Front range ana
the Idaho plains" This by REFER
ence, connects the mass at Butte win
the monzonite in the Occur dAlene
region. Pyrite occurs as primary
constituent of the Butte quartz mon
zonite and in pegmatitic facies OF the
aplitc." In massive veinlets 1t car
ries some copper and lis supposed to
be the mother copper mineral OF the
district" Mr. Weed also states that
"chalcopyrite is a primary mineral III
the Butte quartz monzonte, study
of thin sections and of polished spec
linens showing that it is intergrown
with the rock minerals in the per-
fectly fresh rock" The earliest cop
per veins are mass of pyrite and
quartz carrying less than | per cent
of copper. Though the evidence y
not conclusive, it is believed to indi-
cate that the copper and other min
erals of the uuartz-pyrte veins are
derived from magmatic emanatlons
coming from a deep seated mass OF
igneous magma l am not disposed
To criticise that conclusion. The gold
In the Butte copper ore averages low
but is much greater than in the
Occur dAlene lead ore.
Occurrence Of Gold in the Occur
d'Alene.
In the latter district, gold veins oc~
cur mainly in two groups, both OF
which are rather low in the Prichard
formation, suggesting that minute
quantities Of gold may have been
disseminated in the lower Prichard
strata, but | am inclined to connect
them with the monzonite intrusion.
Nearly all the gold quartz veins In
the Murray district that have been
described are bed veins and lie at
rather low dips They contain small
quantities of pyrite, chalcopyrite, ga
lena, sphalerite and free gold. They