57

McConnell Creek is about 6 miles long and flows south-southeast into
Ingenika River. It has carved its present channel in the bottom of an
older valley, the sides of which slope very gently upwards to the mountain
ranges that parallel the creek at a distance of several miles. Thus, for
about 25 miles from its mouth it flows through a narrow rock canyon;
and for the remainder of its course meanders over the terraced gravel floor
of a rock-walled trench some 2,000 feet wide and 200 or 300 feet deep.
Throughout most of its course it flows near the contact between granodiorite
on the west and schistose and gneissic phases of voleanic rocks on the east.

Most placer mining has been done on the gravel benches bordering
the creek for about 2 miles above the canyon. The gravel is reported (Lay,
1932) to rest on compact concretionary silt or, according to others!, on a
few feet of boulder clay, which in turn rests on the silt, but neither of these
contacts was observed by the writer. The silt is probably a deposit formed
in a former lake, and a shaft sunk by P. Jensen about 2 miles above the
canyon is reported (Lay, 1932) to have encountered about 138 feet of this
material without reaching bedrock. Judging by the shaft dump, the base
of the gravel there approximates creek level. The gravel may not be more
than about 25 feet thick, because it does not as a rule extend to more
than that height above the ereek. It was deposited in rapidly flowing water
in channels that continually shifted from side to side. It is a poorly sorted,
commonly crossbedded mixture of well-rounded boulders, cobbles, pebbles,
and sand interspersed with layers and lenses of sand. The boulders range
up to several feet or more in diameter. The gold is erratically but widely
distributed in various layers from the surface down to the silt or boulder
clay but, so far as can be ascertained, does not occur in the silt. Mining
operations did not encounter bedrock anywhere along the creek, and it is
not known whether gold was concentrated there. A little gold has been
found in nearly all the tributary creeks.

The gold occurs as small, rounded grains, or as larger, generally
flattened nuggets, the largest recovered by C. Fredrikson during many
years of operation weighing less than #5 ounce. It is accompanied by
abundant black sand and occasional flakes of platinum as much as ;5 inch
in diameter. A nugget, about 4 inch in diameter, of a soft silvery mineral
recovered from the gravel by J. Olson was an alloy? of silver and mercury
with a specific gravity of 11-40, or somewhat less than that of arquerite.
A sample of black sand concentrate recovered from sluice-boxes on Olson’s
claim in 1945 assayed*: gold, 7-36 ounces a ton; silver, 0-74 ounce a ton;
tin, none; tungsten, none; platinum (by spectroscope), trace; palladium
(by spectroscope), trace. A spectroscopic examination‘ of a similar sample
confirmed the absence of tin and tungsten, but indicated the presence of
a little vanadium. No systematic attempt has ever been made to determine
the quantity or average gold content of the gravel, but the average of
seventeen pan samples (Lay, 1932, p. 6) taken at widely separated points
was: gold, $1.52 a cubic yard (presumably calculated at $20.67 an ounce) ;
platinum $0.12 a cubie yard (calculated at $40 an ounce).

1 Fredrikson, C., and Olson, J.: personal communication.

2 Identified by I. Poitevin, Mineralogical Section, Geological Survey of Canada.
3 Assay by Bureau of Mines, Department of Mines and Resources, Ottawa.

‘By F. J. Fraser, Geological Survey of Canada.