Ore- Deposit of the Treadwell Mine. 85 
I have examined on the coast of British Columbia, to the 
southward, may very probably be of Triassic age and referable 
to the Vancouver series of the reports of the geological survey of 
Canada.' On tlie northeast side, in the immediate vicinity of the 
Treadwell mine, the ore-mass is bounded by a zone about sev- 
enty feet in thickness of greenish schistose slate, but it is un- 
certain whether this zone owes its character to peculiar alter- 
ation, or to a difference in original composition, as the slaty 
rocks as a wliole, do not show any marked degree of altera- 
tion in the vicinity of the ore. A slate 'horse,' more or less 
completely silicified, is passed through in one place in the 
main working drift, but its character as a portion of the coun- 
try rock is still clearly apparent. The argillites or slaty rocks 
are often found to be flexed and tilted at high angles along 
this part of the coast, and it is probable that the main period 
of elevation of the coast ranges has been subsequent to that of 
their deposition. 
The ore itself presents none of the characters of that of an 
ordinary lode or vein, being without any parallel banding or 
arrangement of its constituent minerals, and showing no such 
coarse crystalline structure as a lode of larger dimensions 
might be expected to exhibit. It is, on the contrary, a nearly 
homogeneous crystalline mass, of medium grain, and pale 
grey in color, evidently consisting principally of quartz and 
white feldspar with a little calcite,cind specked throughout with 
small cubical crystals of iron pyrites. The quartz, however, 
as well as the calcite and pyrites, may occasionally be found 
traversing the mass in small irregular veinlets and stringers, 
and the pyrites in some instances forms little distinct aggre- 
gations or bunches. 
A clue to the true nature and origin of this deposit, (other- 
wise of a somewhat enigmatical character)appears to be afford- 
ed by the existence in it, in some places, of kernels of a dis- 
tinctly granitoid appearance. Some of these were observed 
to be six inches in diameter, and portions of others were found 
which may have had a diameter of several feet. The material 
of these kernels — which around their edges blend imperceptibly 
with the main mass, — is similar in size of grain to that of the 
ore-mass itself, but includes little or no pyrites. It is harder 
and less evidently decomposed, often greenish in tint from the 
'See Annual Report Geo. Siir., Can., 1886. p. 10 B. 
