A lens of limestone forms a north trending, 400 metre long by 180 metre wide, double crested hill on the north side of Cornwall Creek, 3 kilometres due west of Ashcroft. The lens lies in the Eastern belt of the Carboniferous to Jurassic Cache Creek Complex, consisting of a melange of chert, argillite, limestone, greenstone and ultramafic blocks of Pennsylvanian to Triassic age. A 46-metre thick bed of shale, argillite and quartzite striking 125 degrees and dipping 65 degrees northeast is exposed along the central depression.

The hill is comprised of uniform, medium grained, light grey to mottled limestone with a few scattered streaks of chert and some irregular patches of dolomite that become more frequent on the north side of the deposit. Thin films of rusty weathering calcareous shale are also present in the limestone. A 152.4-metre long chip sample across the top of the south crest analysed 55.12 per cent CaO, 0.31 per cent MgO, 0.34 per cent insolubles, 0.52 per cent R2O3, 0.03 per cent Fe2O3, 0.011 per cent MnO, 0.135 per cent P2O5, nil sulphur and 43.55 per cent ignition loss (Minister of Mines Annual Report 1958, page 92, Sample 9).

Sampling of the limestone in 1991 yielded weighted averages of up to 54.55 per cent CaO, 0.20 per cent MgO and 0.50 per cent SiO2 across 20 metres (Assessment Report 22278). In 1992, 0.8 kilometre of magnetometer survey was completed and 49 samples collected and analysed.