Two large lenses of Permian limestone accompanied by several smaller limestone lenses extend west-northwest for between 2.1 and 4.5 kilometres on Mount Harper just south of Paul Lake, 13 kilometres east-northeast of Kamloops. The lenses are exposed over widths up to 1250 metres. They lie within argillite and quartzite of the Devonian to Triassic Harper Ranch Group.

The lenses are composed of light to dark grey, fine to medium grained limestone with variable amounts of chert as nodules and discontinuous thin bands. The chert is largely confined to the edges of the lenses. A sample of chips collected randomly along the south side of the southern lens analysed 51.00 per cent CaO, 1.22 per cent MgO, 5.38 per cent insolubles, 0.44 per cent R2O3, 0.34 per cent Fe2O3, 0.013 per cent MnO, 0.019 per cent P2O5, 0.01 per cent sulphur and 41.76 per cent ignition loss (Minister of Mines Annual Report 1959, page 170, Sample 3).