The Black Diamond occurrence is located 4 kilometres northeast of Toby Creek in the Golden Mining Division. The occurrence is on the south flank of the mountain that separates Delphine and Toby creeks at 2320 metres elevation above sea level.
Regionally, the area is underlain by Proterozoic clastic sedimentary rocks of the Purcell and Windermere supergroups and by lower Paleozoic strata of the Beaverfoot and Mount Forster formations (Geoscience Map 1995-1).
The Purcell Supergroup strata include the Aldridge, Creston, Kitchener, Dutch Creek and Mount Nelson formations. The Windermere Supergroup unconformably overlies the Purcell Supergroup rocks and includes the Toby Formation and Horsethief Creek Group (Paper 1990-1).
In the vicinity of the occurrence, rocks of the Kitchener and Dutch Creek formations have been further subdivided and assigned to the Van Creek and Gateway formations. The Van Creek Formation correlates with the Lower Kitchener Formation while the Gateway Formation is equivalent to the lower portion of the Dutch Creek Formation. The Mount Nelson Formation has been subdivided into seven discrete members, a lower quartzite, a lower dolomite, a middle dolomite, a purple dolomite, an upper middle dolomite, an upper quartzite, and an upper dolomite (Open File 1990-26).
Rocks of the Horsethief Creek Group, Beaverfoot and Mount Forster formations are folded and overthrusted by rocks of the upper portion of the Dutch Creek Formation and the lower members of the Mount Nelson Formation. The sedimentary rocks have undergone regional metamorphism to at least greenschist facies.
The prospect consists of at least five small adits driven on a vertical quartz vein within argillite of the Hg1 member of the Gateway Formation. Mineralization includes pyrite, sphalerite and galena disseminated in white quartz. A 3 to 5 metre wide northwest trending gabbroic dike follows the vein structure for some distance. The dike is usually 1 to 3 metres northeast of the vein but in places it forms the hangingwall of the vein (Assessment Report 23184).
Limited production from the adits in 1906 and 1907 yielded 60,028 grams of silver and 26,672 kilograms of lead from 43 tonnes mined.
In 1995, with support from the Explore B.C. Program, C. Downie, T. Termuende and R. Walker mapped old workings along the Black Diamond structure and diamond drilled 4 short holes totalling 179.1 metres. This work confirmed the existence of strong quartz veins with high grade silver, lead and zinc, and anomalous gold mineralization similar to the nearby Mineral King mine (082KSE001). The veins follow the Black Diamond fault which has been traced for 4 kilometres and 760 metres vertically (Explore B.C. Program 95/96 - M94).
No further work was carried out on the Black Diamond claims between 1995 and 2004. In 2004, the area was covered by a high-resolution versatile time domain electromagnetic (VTEM) airborne geophysical survey. Results from the survey imaged the trace of the Black Diamond structure and a northeast-trending structure (Assessment Report 27729).
In 2006, an exploration program including prospecting and mapping was conducted along the Black Diamond structure, on the north side of Toby Creek. Mapping defined relatively simple stratigraphy with phyllitic dolomitic siltstone dominant in the valley bottom, transitioning upward into thicker bedded dolomite at the midlevel workings from 1800 to 2000 metres, and finally upward into quartz-rich phyllitic siltstone and massive quartzite exposed in the upper workings at approximately 2250 metres (Assessment Report 28788).
In June 2012, a 400-metre drill program was carried out to further test the Black Diamond structure. Results included drillhole BD12-01 intersecting 2.83 metres grading 4.34 per cent lead, 5.13 per cent zinc and 111.1 grams per tonne silver from 170.43 to 173.26 metres, with true thickness calculated to be 1.58 metres. The entire mineralized interval returned 3.98 per cent combined lead-zinc and 49.3 grams per tonne silver over 17.37 metres, with a true thickness of 9.8 metres (V STOCKWATCH, October 23, 2012).
