The Black Rock South occurrence is located near the boundary of the Black Rock No.2 and No. 3 Crown grants on a northeast-facing slope west of Annie Rooney Creek.
Regionally, the area is underlain by fine clastic sediments of the Lower to Middle Ordovician Active Formation, undivided sedimentary rocks of the Cambrian Laib Formation and quartz arenite sedimentary rocks of the Neoproterozoic to Lower Cambrian Hamill Group, which have been intruded by granodioritic rocks of the Cretaceous Anstey pluton and small stocks of syenitic to monzonitic intrusive rocks of the Eocene Coryell Plutonic Suite.
Locally, small lenses of crackled dolomite and black limestone of the westernmost unit of the Lower Cambrian Reeves member (Laib Formation) contain minor discrete blebs, disseminations and irregular streaks of sphalerite, galena, and pyrite. The mineralization is reportedly fracture-controlled and rusty limonitic boxworks are characteristic of zones of higher sulphide concentration. The mineralization has been traced in outcrop and trenches for greater than 80 metres.
In 1984, 8 (of 12) samples from outcrop and former trenches yielded from 0.30 to 2.90 per cent lead, 1.15 to 14.4 per cent zinc, 9.2 to 35.0 grams per tonne silver and 0.024 to 0.122 gram per tonne gold (Assessment Report 12655).
In 1986, a rock sample (BR86-12) from the northern trench assayed 4.25 per cent lead and 7.38 per cent zinc (Assessment Report 15873).
In 1996, a grab sample (2069) assayed 2.19 per cent lead, 6.79 per cent zinc, 13.1 grams per tonne silver and 0.14 gram per tonne gold, whereas a 1-metre chip sample (2131) yielded 2.30 per cent lead, 3.51 per cent zinc and 10.9 grams per tonne silver (Assessment Report 24910).
The area has been historically explored in conjunction with the nearby Emerald Tungsten (MINFILE 082FSW010) and Jersey (MINFILE FSW009) mines. Mineralization was first identified on the Black Rock claims in 1919 by J. Baxter. During 1951 through 1953, American Zinc Co. completed 34 drillholes, totalling approximately 5250 metres. In 1959, extensive trenching was performed on the north side Sheep Creek in an area of sulphide-bearing boulders but failed to identify a bedrock source.
In 1979 and 1980, Mentor Exploration and Development completed programs of soil sampling and trenching on the area. In 1984, Greenwich Resources Inc. completed a program of rock and soil sampling, geological mapping and a ground electromagnetic survey. In 1986 and 1987, Source Resources, on behalf of St. Jame’s Minerals Ltd., conducted programs of prospecting, and geological mapping and rock and soil sampling the area. In 1990, St. Jame’s Minerals Ltd. completed a 7.0 line-kilometre ground magnetic and electromagnetic survey.
During 1994 through 1996, Sultan Minerals Inc. conducted programs of geochemical sampling, geological mapping, a 510 line-kilometre airborne geophysical survey and a single diamond drill hole, totalling 65.23 metres, on the area. Drilling indicated that the mineralized zone is faulted off at a shallow depth.
