The Trembleur Lake showing occurs in a region underlain dominantly by the Mississippian to Triassic Cache Creek Group rocks. These have been intruded by intermediate to felsic intrusions of the Lower Jurassic Topley Intrusive Suite.

The showing consists of sparse pyrite and galena mineralization in quartz veins which cut interbedded quartzite and argillite. These rocks, in areas of folding and faulting, have been metamorphosed to graphitic and quartz-mica schist. The veins vary in width from 5 to 36 centimetres and are both cross-cutting and conformable to bedding. Many large pyritic diorite dikes, probably related to the Topley Intrusive Suite, also outcrop in the area.