The East Gold deposit is located on the west side of the Tide Lake valley, near the headwaters of the Bowser River, 3.5 kilometres north of Tide Lake and 40 kilometres north of Stewart, British Columbia.
There is a lengthy description of the deposit and its history, on the British Columbia “Minfile” site, current to 2017, to which interested readers are referred. Relevant geological sections are quoted below:
“The deposit is apparently located within an isolated fault block that has been affected as a whole by hydrothermal alteration. The rocks are mainly comprised of highly fractured and sheared fine-grained siltstone with minor clastic horizons. Greywacke, argillite and tuffaceous sediments also occur. The major structure in the mine area is a tightly folded anticline made up of minor folds and locally contorted beds. It has a north-northwest trend and plunges to the south. A pervasive sericite, quartz, carbonate, pyrite alteration has overprinted the strata producing a reddish hue to area outcrops.
Three types of mineralization occur at the East Gold deposit:
1) A high-grade vein zone varying from 3 to 60 centimetres in width is bounded on the hangingwall side by a fault with average strike of 165 degrees and dip of 68 degrees west. The vein is knife edge thick on surface and can be traced for 53 metres. Underground it extends from the foot of a raise 12 metres northward where it appears to merge into a diffuse shear zone. The zone is sheared and silicified and contains stringers of quartz and calcite, much pyrite and discontinuous lenses, from 1 to 2.5 centimetres wide, of dark brown sphalerite and some galena. Minor amounts of pyrargyrite (ruby silver), electrum, arsenopyrite, tetrahedrite, chalcopyrite, and native silver also occurs (sic), with electrum forming rich pockets locally. A 30 centimetre sample across the zone taken within the drift assayed 24.00 grams per tonne silver and a trace of gold. A 6.5 centimetre sample including a 4 centimetre stringer of sphalerite and galena assayed 476.58 grams per tonne silver and 2.06 grams per tonne gold. The entire production of the mine up to 1945 has come from this one vein zone. It is not clear whether post 1945 production also came from this source (Annual Report 1946).
2) Several strong and persistent shears cut the sediments, striking from 110 to 125 degrees and dipping from 70 to 85 degrees southwest. The rocks along the shear are silicified and carbonatized in bands ranging up to 30 centimetres in width, with the bands closely spaced over a width 0.6 to 4.6 metres. This zone is thought to extend for about 450 metres. Mineralization occurs in the altered sediments and in stringers and bands of quartz. Mineralization is similar to that of the high-grade vein zone but much less abundant with gold and silver values also being lower. Typical assays are 25.71 grams per tonne silver and a trace of gold over 1.82 metres and 5.14 grams per tonne gold and 3.43 grams per tonne silver over 1.82 metres (Fawley, A.P., 1946).
3) A stockwork of quartz veins occurs in highly fractured sediments about 300 metres southeast of the raise, approximately on strike with the high-grade vein. One vein is 30 centimetres wide and contains chalcopyrite, sphalerite, galena and small amounts of tetrahedrite, arsenopyrite and malachite. Metallic minerals form 5 per cent of the vein.”
According to British Columbia “Minfile”, production from the East Gold deposit between 1949 and 1965 (intermittent) was:
31 tonnes of material shipped, which yielded:
Ag: 3,171 Troy ounces;
Au: 1,019 Troy ounces;
Pb: 2,354 kilograms;
Zn: 1,029 kilograms; and
Cu: 30 kilograms.
Comments by Giles Peatfield on some of the minerals reported from the locality (note that minerals unless noted were reported by White (1947), quoting Fawley (1946):
Baryte: Reported by Wares (1987) in drill core.
Calcite: Sanabria (2008) reported platy box-work or ‘angel-wing’ texture in calcite, suggesting a possible boiling zone deposition from hydrothermal solutions.
Chalcedony: Reported by Sanabria (2008).
Electrum: First reported by Fawley (1946). Material from here was X-rayed (Berry and Thompson, 1962), with a note saying “Composition close to AuAg3 (fire-assay).” The Pacific Museum of Earth at the University of British Columbia has a specimen (catalogue number 1138) from this deposit. Another specimen is in the collection of Dr. J. D. Scott in Ottawa.
Malachite: Reported in a vein by Sanabria (2008), who seems to have been simply quoting from “Minfile”; the original source is not obvious.
Pyrargyrite: “Minfile” reports “Minor amounts of pyrargyrite (ruby silver), electrum . . . .”, but it is not obvious why the “ruby-silver”, as originally reported by Hawley (1946), has been called pyrargyrite, rather than, for example, proustite. The mineral should be regarded as tentative, pending further investigation.
Pyrrhotite: Reported in surface trenching, with pyrite in thin galena seams, by McCrae (2017).
Sericite: Reported by Sanabria (2008) as part of the alteration of the host sediments.
Addendum 16 Sept. 2022 by Giles Peatfield:
Through the kindness of Kirk Hancock, Mineral Resource Geoscientist, British Columbia Geological Survey, I have been given access to several pages of data from Fawley’s M.Sc. Thesis (1946). The following points have come to light:
1) Pyrargyrite: Fawley originally believed that both pyrargyrite and proustite were present, based on microchemical tests showing abundant arsenic, and etch reactions that varied from grain to grain. Subsequently, X-ray photographs were taken which “. . . prove that pyrargyrite is the only variety of ruby silver present, . . . .” He did not, apparently, ever come to determine why the arsenic contents should be so high. This removes the “tentative” label in my earlier comments – pyrargyrite is valid for the locality.
2) Electrum: Fawley (1946) recognized two varieties of electrum. His “Electrum A” is in the form of scales and wisps with maximum dimensions about 0.01 mm, included in sphalerite. It is “. . . deeper yellow than Electrum B and has a faintly reddish tinge.” Fawley’s “Electrum B” occurs as much larger grains, some as large as 3 mm, and is pale yellow in reflected light. Dr. Scott advises that now he has examined his specimen in more detail, he can see both varieties.

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