The Horsethief Creek occurrence is located 28 kilometres west-northwest of Invermere, 104 kilometres north-northwest of Kimberley. The main outcrops are situated atop a prominent hill on the south side of Horsethief Creek. It was discovered and staked in 1988.
The region is underlain by a north trending sequence of argillite, shale, dolomite, limestone and quartzite of the Helikian Dutch Creek and Mount Nelson formations. The Horsethief Creek batholith, a large body of coarse-grained Cretaceous quartz monzonite, outcrops 1 kilometre northwest of this occurrence.
The hill on the south side of Horsethief Creek is underlain by quartzite and dolomitic limestone of the Mount Nelson Formation. Pale brown to light grey, massive and sometimes cherty quartzite extends northward along the east side of the hill towards Horsethief Creek. A large outcrop of limy quartzite is situated on the south side of the hill near its summit. Dark grey to black dolomitic limestone, striking north and dipping 30 to 65 degrees west, outcrops along the west side of the hill.
Skarn mineralization outcrops over the north side of the hill, beginning at the summit and continuing north for at least 1600 metres, over a vertical extent of 180 metres. Tremolite and wollastonite commonly occur in this zone as clusters of radiating fibres, up to 10 centimetres long, and as lenses and veins in siliceous dolomitic limestone. Minor scheelite and garnet occur. Several outcrops, occurring in a 110 by 175 metre area at the top of the hill and along a 30 metre high cliff on the southwest face, contain 15 to 20 centimetre wide, northwest striking veins of massive, white to pale green calcium silicates intercalated with quartzite beds and cut by occasional veins of calcite.
A 36.8 kilogram sample was submitted to CANMET and the results were as follows (Open File 1991-17):
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SiO2 51.8 %
Al2O3 0.68%
Fe2O3 1.58%
CaCo3 20.8 %
MgO 14.6 %
L.O.I. 8.32%
Brightness 75.85%
Lightness 88.48%
The lenticular and vein like nature of the calcium silicates suggest this mineralization is likely a product of siliceous hydrothermal solutions reacting with the dolomitic limestone along fractures. Such solutions likely originated from the nearby Horsethief Batholith.
