Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1937-04-03

some. superficial support thereto may be due
/ to the fact that. in the early days the
mines were working In the more or less.
as depth was gained. the normal. primary
ores we're encountered. perhaps not as read
/ ny amenable TO the processes Of recovery In
has been developed at considerable depth be-
low the then considered bottom" Of deposit
ton OF gold ore. and as unoudized. unleached
and un-enriched primary ore.
shannon Abandonment"
Abandonment" Of the Shannon mine, as
indicated By the course pursued, and reasons
advanced. was based on this theory, not
Withstanding the fact that the DEVELOPMENT
on the bottom-750-ft. Ievel-was 10 prtmary
ore Of the large, Shannon vein, averaging
between seven and eight dollars per ton at
me then current prices OF gold and silver.
ore OF this value, even at that time, also
far more refractory as affecting milling prac-
tice was profitably being mined IN Canada
and the United States from greater depths
the gold values only go to 600 or 800 feet
in depth" the Shannon quit while the
quitting was goodl'
OF the second fallacy. It only need be
pointed out that the North Star vein Of the
Drumlummon mine, was worked to the 1000
It. level. the st. Louis vein the opening sec
tons OF both the Belmont and Bald Noun
tain veins. and the deep workings in the
Chester mine-with high-grade gold ore-all
are between walls of granite, within the
Marysville batholith.
The inception Of igneous activity, viz. the
Intrusion OF the deep-seated granite in
vasion followed BY the various igneous in
trusions and dikes. paved the way for the
consequent Injection OF the notwithstanding,
fissure veins into the upper rock horizons.
The veins are assembled, not only in the
vicinity Of the granite bathohth the Drum
lummon on the east marginal with the step
ly dipping, east contact and the Spokane
Annie Dillon, Belmont and Bald Mountain
veins on the west, radial to the contact but.
also TO the south and west. the ore veins are
closely associated with a series Of parallel
dikes OF Belmont diorte porphyry Darrell
Prof. Paper 81, U. s. Geological Survey /
SouthWesterly from the exposure of Rranite
in Raw Hide gulch, are the Emma Miller
and Mt. Pleasant mines. the Blue Bird and
Honeycomb, the Shannon. and the Bald !
Butte. Channel Penobscot and Bell Boy mines,
each group ike peas in pod, along q |
Observation-Disclosures trending dixie or sys- I
ten Of dikes.
Area Is "a Miles
glance at the map Of the Marysville dis /
triet discloses that the productive mines mot |
including the Jay Could are distributed over |
an area six miles east-west and four miles /
north-south in extent.
Mention has been made Of 1.-The enriched
zone" This occurs near or below the surface,
The depth depending upon the relative prog
ress between teaching and secondary deposit
lion, and the natural, surface erosion-deg-
relation. AS pointed out by W. H. Emmons
sitting Marysville, the teaching Of gold is
effected by the reaction between manganese
present in the primary gangue as rhodocro-
nte, and the hydrichloric acid natural in
underground water, with Liberation OF free
chlorine a solvent of gold. as the solution
nigrates to lower depths in the vein flss1-e
he gold is redeposited Gn coming into con-
act with the primary minerals at non-cir-
ulating water level, as is the dissolved lold
n the cyanide Of the mil solution rrecpi-
ated on contact with zinc charcoal. or or
anic matter. This fact merits due consid-
ration In prospecting the gold veins OF the
darysyiIle district.
VEINS
The gangues Of the Marysvlle district with
lhtch the gold-silver ore IS associated, COM
rise quartz, quartz-cemented breccia which
Includes fragments OF the various rock for
nations through which the veins have risen,
nd In the higher-less eroded--areas, chaI-
edonic quartz accompanied by carbonate
angue minerals, calcite and ankerite. Rho
ocrostte is a primary gangue mineral in
lost Of the veins, its black oxidation product
rominent in the upper sections of the
ems. The veins In the granite of MT. Ed
ards, in the northern part OF the district, !