An elongate mass of medium-grained biotite granodiorite of the Middle Jurassic Cahill Creek pluton extends northwest from the main intrusive body into argillite, siltstone and limestone of the Upper Triassic Hedley and Stemwinder Mountain formations (Nicola Group).

A roadcut along the southwest flank of the granodiorite body, 4 kilometres southwest of Hedley, exposes skarn in fine-grained dark grey limestone of the Stemwinder Mountain Formation over a 100 by 25 metre area. Siliceous and calcareous argillites of the same formation occur in the same roadcut to the southeast.

The skarn is porphyritic and contains phenocrysts of tremolite, actinolite, diopside and epidote up to 3 millimetres long. Traces of galena and chalcopyrite are present, in addition to traces of other sulphides.