The region is underlain by a roof pendant, consisting of volcanic and sedimentary rocks, within the Eocene Coast Plutonic Complex. These pendant rocks have been correlated with Middle-Upper Jurassic Hazelton Group rocks and overlying upper Middle to Upper Jurassic Bowser Lake Group sedimentary rocks (Geological Survey of Canada Open File 3453). The Hazelton rocks consist of variably chloritized pillow and massive basalt with minor mafic tuffs. The overlying Bowser Lake sediments consist of siltstone and sandstone with minor chert and limestone.

The slag pile at the Anyox smelter was originally a single massive sloping slab of glass which resulted from the smelting of the Hidden Creek (Anyox) deposit (103P 021) ore. Sixty years of weathering has devitrified this material into sharply angular coarse to fine glass splinters. The high content of impurities in the silica flux have created a slag with a hardness significantly lower than quartz. This characteristic, combined with the highly angular shape of the glass shards, makes the screened, sorted fine abrasive ideal in an abrasive slurry for sand blasting. The angular particle shape strips old paint or other oxidized surface coatings better than rounded sand grains; yet the lower particle hardness removes less underlying metal than conventional quartz sand.

The primary user for this abrasive is the United States military. The abrasive was used for the regularly scheduled stripping and repainting of the special sonar-absorbing coating applied to the hulls of the U.S nuclear submarine fleet stationed in Puget Sound.

The quarrying permit was first issued to Tru-Grit Abrasives in July 1990. Primary production season was over the summer months, but extended well into the spring and fall. The quarry was still active in 1998. D.J. Alldrick of the British Columbia Geological Survey gives a conservative estimate of 20 million tonnes of slag (personal communication, 1998).