The Mastadon occurrence is located at the head of La Forme Creek, approximately 29 kilometres north east of Revelstoke.

The showings were discovered in 1898, and were known as the Noble Three group. Little of this early history has been recorded. In 1918 the property was acquired by Mastodon Mining Company and the first development work of an inclined shaft was done. Work since then was sporadic and consisted of surface trenching. In 1941, the claims lapsed, and were relocated by D.F. Kidd. A drilling program was attempted in 1942 but abandoned after the eighth hole due to poor drilling conditions and core loss in critical areas. The property was optioned to New Jersey Zinc in the late 1940‘s, with minor surface trenching being performed before the option was terminated. In 1952-1953, Mastodon Zinc Mines Ltd. developed the property, including the production of 34,400 tonnes ore. In 1960 the mine was closed permanently and all facilities dismantled. In 2008-2010, Rich River Exploration Ltd. performed a series of geochemical and geological surveys on the showings as apart of their Allco-Redtop-Slide Project.

The orebodies lie on the west side of a lenticular mass of Lower Cambrian limestone and dolomite of the Badshot Formation in contact, both east and west, with dark-grey and green phyllites of the Lower Cambrian and younger Lardeau Group. The rocks are isoclinally folded and strongly sheared. Several strike faults cut the rocks trending northwest and dipping at moderate angles to the northeast parallel to foliation. The strike faults appear to be the primary control for zinc mineralization.

The mineralized zones are replacements of limestone, dolomite and phyllite mainly by sphalerite and occassionally galena and grey copper. The sphalerite, ranging in colour from light yellowish-brown to dark brown, is disseminated and massive within the limestone and occurs as the matrix of breccia associated with the strike faults. Some mineralized zones are in folds or in banding related to cleavage, both of which are cut by the faults. The orebodies dip to the north- east and rake to the north. They are tabular or lenticular and commonly split or branch.

In 1952-1953, Mastodon Zinc Mines Ltd. produced a total of 34,400 tonnes averaging 10.0 per cent zinc and approximately 0.3 per cent lead and 0.04 per cent cadmium (Assessment Report 32051).