A band of limestone 12 to 15 metres thick is exposed for a length of 300 metres. The white limestone is coarse-grained, contains many siliceous impurities and is cut by numerous dykes.

A gently westward dipping 12 to 15 metre thick bed of limestone is exposed for 300 metres along the east shore of Princess Royal Island on Lots 146 and 147, 11 kilometres south of the village of Swanson Bay. The bed is overlain by schist in contact with granite of the Coast Plutonic Complex. Dykes frequently intrude the limestone.

The deposit is composed of white coarse grained limestone (marble) containing inclusions of schist and quartzite that parallel the bedding. Quartz veins and streaks of mica and pyrite are common. A sample of the purest limestone exposed in a quarry contained 53.88 per cent CaO, 0.72 per cent MgO, 1.56 per cent SiO2, 0.25 per cent Al2O3, 0.18 per cent Fe2O3 and 0.02 per cent sulphur (Canmet Report 811, p. 176).

Limestone was produced here from two quarries earlier this century for the pulp mill at Swanson Bay.