23 
so as to enclose lenses of unsheared rock. It parallels the ore-body closely, 
but is clearly of later date, as the reddish ore is crushed to a red gouge 
within the fault zones, lenses of unsheared ore are found surrounded by 
sheared material, and the graphite fault cuts unbroken across other faults 
which have themselves cut across the ore-body and caused displacements 
of 2 to 6 feet. Some mineralization took place later than the graphite 
fault, however, as the schist of the fault in places contains lenses of glassy 
quartz accompanied by some calcite and a little free gold. 
The rocks are of two kinds, greenstones, considered as altered Kee- 
watin lavas, and thin-bedded tuffs. The tuffs are blackish, due to a small 
content of carbon. The fault, within the mine, lies mainly in these tuffs 
and so much graphite is developed along the planes of shear that cars of 
waste coming from the shear zone look like cars of coal. In two or three 
places , however , where the fault or a branch of it passes from the tuffs into the 
greenstones for any considerable distance , graphite disappears; and the con- 
clusion seems inevitable that the graphite of the fault is related in some 
way to the tuffs. As the tuffs contain carbon, the graphite may have been 
concentrated by elimination of some of the other constituents during the 
shearing. 
Accordingly, specimens showing the gradation from unsheared to 
sheared material were collected, though difficulty was experienced in 
securing reliable samples, owing to the universal presence, between the 
leaves of schist, of paper-thin lenses of light-coloured vein material. Finally, 
on the 1,000-foot level of the mine, a place was found, near mine station 
1010, where such contamination appeared to be a minimum. It was also 
considered that if material were really eliminated during shear, some of 
this material would naturally be deposited along the planes of shear 
probably toward the close of the shearing, when pressure began to de-, 
crease; hence much of this contaminating vein material may not be foreign 
matter, but part of the rock itself arrested during departure. The analyses 
below seem to confirm this supposition, for although all the sheared samples 
contained more or less vein-like matter, only one, No. 5, exhibits any 
pronounced aberration such as would suggest introduction of foreign 
material. It contains about 6 per cent more silica than would normally 
be expected, on this hypothesis. 
The samples taken from the graphite fault are Nos. 1 to 6. Nos. 1 and 2 
are of unsheared black tuff, taken as checks on one another; Nos. 3, 4, and 
5 consist of partly sheared material; No. 6 is the most schistose material 
present, and consisted of chips about as thin as postcard, pried loose with 
the point of a penknife from the slickensided faces of shear-planes. 
Under the microscope the unsheared tuffs appear to consist largely 
of sericite or talc and carbonate, with some quartz, some obscure material 
that may be feldspar, and a little blackish material, probably carbon. A 
little pyrite is commonly also present. The sheared materials are too 
much obscured by graphite for microscopic identification. 
At another point on the 1,000-foot level, near mine station 1016, a 
branch of the main fault cuts the greenstones, shearing them to a fissile 
schist. Some of this material was also taken as a second instance of the 
effect of shearing, and the results are seen in analyses 7, 8, and 9. No. 7 
consists of the unsheared greenstone; No. 8 of sheared greenstone contain- 
