Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1941-12-27

high magnesium and iron eOntent) !
The Beartooth mountains chrome
belt also includes vast deposits in the
Rock creek area, where the Vanadium
corporation is developing properties
held by Montana Chrome, Inc. The
Rock creek work is being carried on
by private enterprise while exploration
and drilling work In the Saltwater
complex is being sponsored and fl
nanced bv the government as part OF
the defense program.
The geological survey a branch Of
the department of the interior, has
conducted exhaustive studies Of the
chromite belt in the Saltwater area
of the Beartooth mountains.
The survey, bureau Of mines and
other governmental agencies immedi-
ately brought the Beartooth deposits
to the attention Of defense officials
when the need for the vital defense
metal, chrome. became acute.
An abstract of a geological survey
bulletin written by j. W. Peoples and
A. L. Rowland on the chromite de-
posits of the saltwater complex fol-
lows:
Although the chromite deposits
show many variations, they all form
steeply- dipping layers and lenses par
allel to the general layering Of the
complex.
Chromite has been found at inter-
walls for q miles along the same gen.
eral horizon in the complex, but in
stead of being one continuous body 1t
forms a series of overlapping lenses,
as anothosite does In a higher zone.
An almost constant associate of the
chromite is a very coarse grained harZ-
burgite with disseminated chromite
grains. This rock may occur above,
below or within the chromite- bearing
layer.
The richest streaks of ore, which
contain about IS percent of chromite
by volume, grade into very lean ma
terial. In the thick layer Of chromite
ore in the eastern part of the War
Eagle claim the rich streaks are at
or near the top to the north. The
thinner chromite- bearing layers COM
monty contain a rich streak on the
footwall, with a few inches to a few
feet of rock containing disseminated |
chromite above it. There are almost /
continuous gradations in places from !
nearly pure chromite to rock scattered |
chromite crystals. On the west side |
of the saltwater valley, a series Of !
chromite bands from a quarter Of an |
inch to about two feet In thickness
alternate with bands of fresh harbour
Cite and basic pegmatite. The harz-
burgite itself contains accessory /
chromite.
The mineralogy OF the chromite
bands is simple and is similar to that
Of the complex as a whole, except in
the proportion of minerals.
Even the highest grade ore contains
some silicate material. The commonest
silicate in the ore from the Benbow
claim Is serpentine derived from the
of Divine and bronzite.
These minerals are not completely al
tered in all of the ore; frest enstatite
and Divine are associated with the
chromite on the Mouat properties on
the west side of the Saltwater canyon.
The chromite of the complex is Of
(molten rock material orig [
mating within the earth) origin.
Chromite is one of the essential pri-
mary minerals Of the area, concen-
trated in many sheetlike masses Of
almost monomineralic rock, although
each rock grades into others.
If the chromite deposits were formed d
at the same time as the
enclosing rocks, it seems reasonable to c
assume that they extend to as great I
d depth as the ultramafic zone Of the |
complex.
Although chromite concentrations q
an be found in the middle part of the C.
zone along most of the
ength of the complex, there is no Il
;ingle chromite-rich band continuous d
throughout .
The chromite deposits differ in L
along the strike. Near the Il
asst end of the Benbow claims chrom- Il
Re occurs over a thickness OF IS to Il
0 feet as layers and irregular lenses II
D misunderstanding harzourgite. At Z
ONE places on these claims the o
hronite is concentrated in a single q
aver seven inches to five feet thick -
nth sharp walls, but more commonly
AYERS Of chromite-rich and chromite-
COR rock alternate over a width Of
to Is feet.
on the west side of the Saltwater
Iver chromite is distributed through
much greater thickness of ultra
lafic rocks and is concentrated in
/ least three zones, the lowest Of
HIGH contains chromite in irregular
.reaks and pods and as disseminated
rains through variable thicknesses.
he two upper zones, which are about
% feet apart, contain comparatively
,gular alternating layers of nearly
lid chromite and chromite-rich harz-
irgite through a thickness ranging
ON few feet to more than so feet.
Although it is believed that there
Is never a continuous chromite layer,
" columnar section Of the complex
,uld probably show at least one layer
chromite. Chromite Is apparently