The Swamp Point quarry is located at Swamp Point on the east shore of Portland Canal, about 50 kilometres south of Stewart.

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. The Hazelton rocks consist of variably chloritized pillow and massive andesite and basalt with minor mafic tuffs. The overlying Bowser Lake sediments consist of argillite, siltstone and sandstone with minor chert and limestone. These rocks strike north to northeast and dip 40 to 85 degrees east. There are two observable phases of folding in the area, an initial north-northeast trending phase followed by a later east-northeast trending phase.

At Swamp Point, a 60 metre thick bed of white to dark bluish grey, medium to coarse-grained limestone strikes 360 degrees and dips steeply to the east. Foraminifera from this limestone unit have indicated a Lower Jurassic age (T. Grove, personal communication, 1989). The bed is folded and cut by a few thin dikes. Silicious streaks containing pyrite, actinolite and mica are common throughout the limestone. A channel sample taken across limestone free of the silicious bands contained 97.77 per cent CaCO3, 0.53 per cent MgCO3, 0.95 per cent SiO2, 0.19 per cent Al2O3 and 0.27 per cent Fe2O3. A second channel sample taken across limestone with the siliceous streaks contained 93.12 per cent SiO2, 0.94 per cent MgCO3, 4.06 per cent SiO2, 0.54 per cent Al2O3 and 0.92 per cent Fe2O3 (CANMET Report 811).

Limestone was produced from two quarries operated by Granby Mining, Smelting and Power Company Ltd. between 1916 and 1922, for use as flux at the company’s copper smelter at Anyox (103P 021). A total of 257,316 tonnes of limestone was quarried.