Dolomite of the Middle Ordovician to Silurian Beaverfoot Formation forms a spur that rises southeastward along the south side of Geary Creek, just northeast of the north end of Columbia Lake. The dolomite is exposed along the crest of the spur over a length of 3.8 kilometres, with a width of up to 1200 metres. Bedding strikes 105 to 120 degrees and dips 30 to 45 degrees north. The unit is in fault contact to the northwest with dolomite of the Middle-Upper Cambrian Jubilee Formation and slate, quartzite and conglomerate of the Hadrynian Horsethief Creek Group. Underlying limestone and argillite of the Upper Cambrian to Middle Ordovician Sabine Formation (McKay Group) outcrops to the south.

The deposit is comprised of very fine grained, dark bluish grey, thickly bedded dolomite. Chip samples collected from various places over the spur analyzed 30.39 per cent CaO, 21.26 per cent MgO, 1.40 per cent SiO2, 0.40 per cent Al2O3, 0.30 per cent Fe2O3 and trace sulphur (CANMET Report 811, page 214, Sample 93).