A brown weathering serpentinite body, of probable Permian age, outcrops in the valley of Little Sheep Creek and is thought to be part the ultramafic intrusions of the Slide Mountain terrane. The serpentinite is in contact with altered volcanics of the Lower Jurassic Rossland Group, Elise Formation. These rocks are intruded by a syenite mass of the Middle Eocene Coryell Intrusions.
Two masses of serpentinite lie within the Rossland map area and have relatively straight and transgressive margins. These lenticular masses form part of a linear belt extending 10 kilometres southwest from Rossland where it is truncated by the Coryell Batholith. The serpentinite is thought to have been emplaced along the Rossland break, which was the locus of dislocation and intrusion before the emplacement of the Coryell syenite. The northerly trending eastern and western margins of the small serpentinite mass in Little Sheep Creek are known to be faults. The northern contact exposed in the workings of the Midnight (082FSW119) and I.X.L. (082FSW116) mines is highly sheared and associated with a zone of intense fracturing.
The typical massive serpentinite is a very dense black rock and hosts abundant serpentine and magnetite. Cross-fibre asbestos has infilled many joints as 0.2 to 0.6 centimetre veinlets and light green talc has developed in the immediate vicinity of the faults.
The serpentinite has been explored for deposits of nickel and chromium. Chromite occurs on the west side of Ivanhoe Ridge between the two main forks of Sophia Creek (Vandot - 082FSW130). Here visible chromite is exposed in trenches. In 1969, near the northern mass of serpentinite on the Midnight property (082FSW119) along the west side of Little Sheep Creek, companies sampled the underground workings and reported several thousand tonnes of serpentinite averaging 0.25 per cent nickel. Selected samples assayed as high as 0.45 per cent nickel (Bulletin 74, page 23). Chromite is associated with the fine-grained serpentinite. Samples were submitted to the Geological Survey of Canada and pyrite, millerite and a mineral of the linnaeite group were identified. Ten samples taken by Fyles (Bulletin 74) at various places throughout the two masses of serpentinite exposed in the area gave nickel assays of less than 0.24 per cent.
