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Billy Mac Group (Locality 178)

References: Annual Report of the Minister of Mines, British Columbia, 1927 and 1931;
Geol. Surv., Canada, Sum, Rept. 1928, pt. A.

The Billy Mac group of six mineral claims is at an elevation of 2,200
feet on the southern slope of McGrath mountain. The group adjoins and
lies north of the Standard group and west of the Highland group. The
main McGrath Mountain trail crosses the property. Development consists
of open-cuts and short adits.

The showings on the property are principally in a body of argillaceous
rock about 1,000 feet broad and which appears to be an inclusion in an
irregular stock of augite porphyrite. The augite porphyrite body may,
however, be in the form of sills or dykes bounding the argillite mass on two
sides. Some of the rock in appearance and mineral composition suggests
that it was originally argillite but has been thoroughly soaked and altered
by fluids emanating from the augite porphyrite. The structure of the
argillite is unknown but has the appearance of being a low dome.

Sphalerite associated with quartz and calcite is exposed in a dozen
open-cuts and short adits. Only one body has been traced as far as 200
feet. It is 20 feet wide, strikes northeast, and dips 30 degrees southeast.
For a breadth of 5 feet along the hanging-wall the deposit is well mineral-
ized with sphalerite; the remaining part is largely calcite containing many
rock inclusions. The deposit may be the result of replacement along a
crushed zone or along a particular stratum.

About 300 feet northeast of this deposit are two other exposures of
vein matter. They are on opposite sides of a creek and may be parts of
one nearly horizontal mineral body. The mineralization consists of quartz,
calcite, and sphalerite. About 200 feet northeast of these showings are five
exposures of vein matter belonging to one or more deposits of unknown
size and shape. About 150 feet farther northeast is a line of open-cuts
trending northeast, which may be in a single mineral body. Individual
showings in these open-cuts are up to 8 feet wide and consist of quartz,
calcite, sphalerite, and country rock inclusions. The mineral bodies are not
well exposed. They have formed chiefly by replacement and may have
formed along beds or along fracture zones.

Sphalerite is the only known mineral of possible commercial importance
on the property. So far as known the best ore is of milling grade and,
therefore, only if large ore-bodies are present would mining operations be
warranted. As the body of sedimentary rock in which the deposits occur
may be an inclusion, its depth may not be great. If the deposits extend into
the augite porphyrite, they may change greatly in size.

Black Bear Group

Reference: Annual Report of the Minister of Mines, British Columbia, 1916.

The Black Bear group of mineral claims of McGrath mountain is
now parts of other groups. In 1916 there were eight claims in the group,
and the mineral showings were said to be quartz and calcite bodies of
unknown size mineralized with sphalerite and some galena.