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lies north of the Porter Idaho. A controlling interest in the two properties
was purchased in 1927 by the Premier Gold Mining Company, Limited,
which soon afterwards commenced extensive underground development
work and constructed an aerial tram to the mouth of Marmot river to
serve both properties.

Tuffs, breccias, rhyolite, and andesite intruded by a few lamprophyre
dykes underlie the claims. On the Prosperity group and from there to
the top of the mountain the volcanic rocks strike northeast along the
hillside and dip at moderate angles northwestward into the mountain.
The dykes are nearly vertical and strike north-northwest. A short distance
south and southeast on the adjoining Porter Idaho and Aberdeen properties
the rocks are sheared locally, but on the Prosperity group shearing is not
evident.

A fault, known locally as the Big Rig fault, striking east and dipping
75 to 80 degrees north, occurs on the lower part of the Porter Idaho property.
The surface expression of the fault is a long, shallow depression. In most
places in the mine workings the fault is a shattered and crushed zone 30 feet
or more in width; in one place, 250 feet below the surface, it is a fracture,
6 feet wide, full of hard gouge. A narrow shear zone occupied by an ore-
bearing vein known as the Winze vein lies north of the fault and as it
approaches the fault swings from a southerly to a southwesterly strike.
The rock where the shear zone and the fault zone come into contact is
crushed to such an extent that the relation of shear zone to the fault zone is
not evident. ‘They may have originated at the same time, in which case
the shear zone might be considered as a branch of the fault. The fault,
however, may be later than the shear zone. That the shear zone is not later
than the fault seems fairly certain, as this shear zone and several other
similar zones are known north of the fault, whereas none is known to cross
the fault. A lamprophyre dyke crosses the fault, has not been offset by it,
and is consequently younger. Underground, however, the dyke is broken
and crushed where it crosses the fault, showing that slight movement con-
tinued along the fault after dyke intrusion.

Several parallel, narrow, shear zones north of the Big Rig fault are
occupied by ore-bearing veins. The veins vary in width from a few inches
to 20 feet but in general are less than 5 feet wide. The veins show much
oxidation down to a depth of 400 feet or more. The principal vein was 2
to 6 feet wide and consisted of quartz mineralized with pyrite, sphalerite,
galena, tetrahedrite, ruby silver, and other silver minerals. The vein in
most places is somewhat oxidized, so that the primary vein minerals are
obscured. The fracture in which the vein lies appears to be a shear zone
of fairly constant width and but little wider than the vein itself. In places
where the vein is widest it nearly fills the shear zone. Where the vein nar-
rows, the shear zone, although it is rusty over its entire width, contains
only a few narrow stringers of ore.

The first ore shoot discovered in the vein was about 5 feet wide and
at least 50 feet long on the surface and considerably longer at depth. It
consisted of very high-grade silver-lead ore containing about 400 ounces
of silver a ton and 25 per cent lead. The ore shoot appeared to be simply
a swell or wider part of the vein. The boundaries of the ore shoot did not