Sample No. 4 from the Burns Mountain long crosscut represents pyrite from the
Perkins set of veins at a depth of about 275 feet beneath the surface. It was treated
in exactly the same manner as No. 5. In it, however, the finenesses of the +60- and
-++100-mesh gold flakes check reasonably closely, averaging about 890 parts gold per
thousand. Also there is a reasonably close correspondence between the metallics and
the average of five determinations of the fineness of the gold in the —100-mesh pyrite
pulp of 870+30 parts per thousand.

Further investigation of the variation in the fineness of the lode gold from the
main Perkins vein was impossible because of the absence of reliable specimen material.
That the fineness of gold from an individual vein and even from an individual stope
may vary widely is reported in the Alleghany District, California, by Ferguson and
Gannett.* In the Kolar goldfield in India gold fineness variations of considerable
latitude, as reported by Pryor (1924, p. 110), are related to depth on the lode, gold of
progressively higher fineness being obtained at deeper levels on the vein system. The
variations of the lode gold from Burns Mountain do not fall into a regular pattern.
They may be explained on the hypothesis either that they represent differences in the
fineness of the original gold as deposited, or the hypothesis that wholly or partly they
represent changes brought about by the differential solution and redeposition of gold
and silver in the zone of oxidation at and near the surface outcrops of the veins. The
necessary manganese for chemical reactions of this type could be supplied by the
manganiferous ankerite, such as is represented by the material analysed from the
Burns Mountain long crosscut (see p. 26). -

Sample No. 6 is a specimen containing visible gold in rusty quartz from one of the
north-north-easterly striking veins exposed at the surface on the Acme group. The
gold in it has a fineness of 927.4-+-0.6 parts per thousand.

Spectrochemical analyses made of samples No. 2 and No. 6 in Table II to determine
if any minor elements were present in characteristic amounts did not show any sig-
nificant differences between the two. The tabulated results follow :—

Sample.* | SiOz. | FeoOsz. MgO. | AloOz. | Au | Ag. | Cu | Pb | He

| | | |
ING Ooh. et Sheesh 120.3f | 2.5 | 25.7 eS | BRIG oe een bys 52a eee Op eae et Geh
INGE ate ae be ne ALOU gel cel Oldie Peas OsSiy sli ce emer 8052) eal lec6-d Ao ee carla (12.0

Ni, Ti, Cr, Bi, Sb, Co, Zn, Mn not present in either sample.

* Each sample weighed 10 milligrams and 50 per cent. of the light emitted was used to produce a spectrogram.
Each sample was treated for five minutes in hot 1:2 hydrochloric acid, decanted, washed, and then treated with
hot 1:2 nitrie acid for five minutes.

{ Figures in the table are spectral line intensities and are directly proportional to the amount of metal in the
sample. They are subject to an error of about 15 per cent.

Undoubtedly a large part of the silica represents contamination of the sample by
the quartz gangue.
GEOLOGIC DISTRIBUTION OF AURIFEROUS VEINS.

Quartz veins in the Stanley area are not only widely distributed areally but occur
in rock-types of a considerable variety. The Foster Ledge veins in Oregon Gulch and
the Perkins veins on Burns Mountain are in a series of fairly thinly bedded quartzites
and argillaceous schists; the Acme group veins are in hard, fairly thickly bedded light-
grey quartzites; the Cariboo Ledge veins are in sheared quartz pebble conglomerate;
veins on the Eldorado claim (Lot 11350) and on Lot 1685c at the head of Olally Creek
are in black argillaceous quartzite, and in Spruce Canyon there are short veins in
chlorite schist. “B” veins such as these are scarce in soft, thinly fissile micaceous
schist, but amongst the harder more quartzitic types it cannot be demonstrated that
any one particular rock-type contains more veins than another. In this regard the
area differs from the Barkerville Gold Belt, where the greatest number of veins occur
in a single rock unit, the Rainbow member.

* U.S. Geol. Surv., Prof. Paper 172, p. 51, 19382.
29