At the Harmon Lake occurrence, three lenses of limestone enclosed in volcanics of the Upper Triassic Nicola Group outcrop in the vicinity of Harmon Lake, just northwest of the road that passes west of the lake.

A lens of light creamy grey limestone, 150 metres long and 60 metres thick, forms a prominent bluff 600 metre north of the road. A second lens of light creamy grey limestone located 60 metres northwest of the first lens extends northeastward for 400 metres with thicknesses of up to 120 metres. Protruding lumps and grains of dolomite and silica give the limestone a rough weathered surface. A sample of randomly collected chips taken across the lens near its centre analysed 54.40 per cent CaO, 0.23 per cent MgO, 1.92 per cent insolubles, 0.26 per cent R2O3, 0.12 per cent Fe2O3, 0.023 per cent MnO, 0.026 per cent P2O5, trace sulphur and 43.08 per cent ignition loss (Minister of Mines Annual Report 1958, page 96, sample 5).

A third lens of dark grey limestone in tuff and sandstone, outcrops over a length of 90 metres and a width of 40 metres, 800 metres northwest of the second lens. The limestone is cut by calcite stringers and contains some dolomite and silica.