Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1940-12-21

: nually. OF four concentrating mills
| built at different times two remain
each of about 50-ton capacity. One
Of these. the Trout mill, at the
/ Trout mine near the center of the
district. uses tables and flOtatiOn;
( the other, the Moonlight mill, at
the south edge Of town, uses both
wet process and dry magnetic
separation The two mills operated
near capacity in 1899.
THE total output OF manganese
ore from the Philipsburg district
prior to Oct 81, 1889, has amounted
to 477,000 long tons of high-grade
ore and concentrates 116, 1862 long
tons OF tailings averaging about 20
percent of manganese, and 1876
long tons OF low-grade crude ore
containing about 20 percent of man
ganese.
Origin of the Ore Deposits
There seems little doubt that
the primary ore of the Philipsburg
district was deposited from hydro
thermol solutions that rose from
depth alcng the vein assures. The
original source of the manganese
was the granodiorites bathOlith, as
indicated by the presence of the
manganiferous silicates thulite Ga
variety of ozisite) and spessartite
manganese garnet) in the contact
metamorphic zone. The early ore
bearing solutions introduced quartz
and the sulphide, which were chiefly
confined to the vein fissures, ex-
cept in the northern part of the dis
trict, where they commonly follow
ed bedding planes. However. the
later solutions, which carried the
bulk of the manganese deposited
manganese carbonate by replacing
the more permeable parts of the
limestone wall rocks adjacent to the
veins and along bedding assures in
the thin-bedded limestones.
Depth OF Oxidation
Most of the manganese-oxide ore
has been mined within 500 or 500
feet of the surface, though one
body was mined at a depth of 700 |
feet; on the other hand, some resi-
dual rhodochrosite has been found |
at a depth of only 100 feet.
I'm the southern part of the dis
trict. where the water table is close |
to the surface, ground-water cir
has permitted oxidation |
from 100 feet to a few hundred |
feet below the water table, notably |
in the Trout and Algonquin mines.
In the extreme northwestern part |
of the district water stands in the |
shaft of the Hope mine |
at an altitude of $500 feet, and |
Pardee estimates that in the lime
stone area oxidation is nearly COM
plete down to this average alti- !
tude, or throughout a zone that
averages 750 feet in depth. The
study of the district serves
to substantiate Pardee's estimate.
and it therefore seems likely that
future prospecting may reveal OK
ide ore bodies to such a depth.
Location of the Ore
The localization of both the ir-
regular replacement bodies and the
bedding vein deposits seems to
have been largely controlled by the
functions of vein assures with bed
ling faults The location and size
- tAAC OA1 DOhANo oOCAA I'll Gully ]
ated to brecciation and fracturing
hat accompanied movement along
both type of assures. Thus the
most favorable horizons are ada
,ent to planes of weakness in the
,ormations-such as thin shale
ayers, contacts of thin-bedded and I
nassively bedded limestone, or con-
acts of thin-bedded and massively
Dedded limestone, or contacts OF
-hin-bedded limestone and lime-si-
icate layers. These favorable no.
lions are ID the middle of the
ihaly limestone of the Silver Hill
formation underlying contact-me-
layers, CD the base
Of the marbleized Hasmark forma-
ton, CD the top of the Hasmark
marble, (4) the top of the shady
limestone in the Red Lion forma-
ton, 60 the base of the marble