The quarry is located at an elevation of 152 metres near Slatechuck Creek, 2.4 kilometres from Kagan Bay in Skidegate Inlet.
Before 1872, the quarry was excavated by the Haida Indians to a size 1.5 by 76 metres by 1.2 metres deep. Sometime later the mineral claim was Crown-granted. The Indians used the slate to carve and polish ornaments, pipes and musical instruments.
An 1872 assay of the black slate gave the following results: silica, 44.78 per cent; alumina, 36.94 per cent; peroxide of iron 8.46 per cent; lime, trace; magnesia, trace; water, 7.15 per cent; carbonaceous matter, 3.18 per cent.
In the early 1900's the slate was shipped by a Victoria company for manufacturing in Victoria.
This deposit of black carbonaceous slate is hosted in an unnamed unit of Eocene to Oligocene age, comprised mostly of shale (Unit Tsh, Geological Survey of Canada Paper 90-10, pages 31-50, Figure 9). The slate is part of a sequence of grey siltstone and fine sandstones, slightly metamorphosed, which appears to overlie an overturned anticline of the Honna Formation, not far from a faulted contact of the Masset Formation.
The slate occurs in lenticular patches up to 1 metre in thickness and 6 metres in length. With the slate, occur an abundance of flattened stems and leaves and many irregular small patches of anthracite. The slate is composed of silt-sized fragments of kaolinite and lesser montmorillonite in a macerated very fine carbonaceous clay matrix that forms 40 to 75 per cent of the rock. The rock has a hardness and a specific gravity of 2.88 to 2.89.
The slate or argillite is used by the Haidas for carving. The Haida Natives have a Crown-granted mineral claim centred on the quarry.
A study done by the British Museum showed the argillite specimen they examined to consist largely of pyrophyllite with some iron serpentine (Harding, 1989).