216

sample from one of these veins, consisting of white fractured quartz con-
taining massive pyrite and thin sheets of molybdenite, assayed: gold, 0-06
ounce a ton; silver, 0-35 ounce a ton; and copper, 0-71 per cent. This
highly sheared band is separated by 10 feet of pyritized, slightly sheared
rock from another, intensely sheared zone to the west containing a heavily
mineralized quartz vein with a maximum width of 4 feet. This vein,
forming the western side of the ‘vein No. 10’ shear zone, has been followed
southerly by a drift, from the crosscut mentioned above, for 35 feet to
where it pinches to a narrow, gouge-filled shear containing no quartz. A
sample across 2 feet of this vein assayed: gold, 0-65 ounce a ton; silver,
0-50 ounce a ton; and copper, 1-78 per cent. Some parts of the vein are
relatively rich in molybdenite and magnetite. What may be the south-
westerly continuation of the ‘vein No. 10’ shear zone is penetrated by a
crosscut extending 140 feet west from the southern end of ‘vein No. 12’.
A 20-foot drift driven northward from the crosscut along the ‘vein No. 10’
shear zone exposes a sparsely mineralized quartz vein about 4 inches wide.

Several shear zones, some containing mineralized quartz veins, occur
at intervals along the banks of Croydon Creek within 2,000 feet upstream
from those explored by underground workings. Some of them apparently
contain considerable magnetite, for areas up to 400 feet wide of strong
magnetic attraction have been outlined. A limited amount of trenching
and stripping has been done on these shears, but due to excessive sloughing
little information can now be gained from the workings.

Mineralographie study of samples from the deposits on this property
indicates two distinct and perhaps unrelated periods of metallic mineral
deposition. The most widespread mineralization is that which resulted in
the deposition of the pyrite, chaleopyrite, and an unidentified, soft, silver-
coloured mineral that may be a telluride. The chalcopyrite was apparently
deposited contemporaneously with and after the pyrite. The molybdenite
and magnetite seem to have been formed during a separate period of
mineralization; the former is invariably accompanied by magnetite in this
deposit. Part of the magnetite is in grains so minute that microscopic
flakes of apparently clean molybdenite are affected by a magnet. Owing
to the difficulty of polishing masses of soft molybdenite containing grains
of hard magnetite, the relations between the molybdenite-magnetite masses
and the pyrite-chaleopyrite masses were not satisfactorily observed, but
it appears that stringers of molybdenite are interrupted by masses of pyrite
in such a way as to suggest that the molybdenite-magnetite mineralization
was the earlier of the two processes.

The precious metal content of these deposits is apparently contained
mainly within the metallic minerals. Grinding of representative samples to
minus 150-mesh, followed by tabling, achieved an almost complete separa-
tion of metallic from non-metallic material. Assays! of the products from
this separation showed almost all the gold to be in the sulphide-magnetite
fraction. The gold-copper ratio of the deposit appears to be fairly constant:
for each 1 per cent of copper in the ore, 0-10 to 0-30 ounce of gold is
carried in the sulphides. Chaleopyrite is probably the main gold carrier.
Thus, material from this deposit would require concentration, and relatively
higher grade material would be necessary to constitute ore than if the

1 Run by Mr. Lawrence Adie in the laboratories of the Department of Mining and Metallurgy at
the University of British Columbia.