The deposit consists of a mass of limestone of the Upper Pennsylvanian to Lower Permian Azure Lake Formation (Buttle Lake Group) occurring at the southern end of the Buttle Lake uplift (Refer to the H-W deposit (092F 330) for a discussion of the nomenclature revisions of Buttle Lake uplift stratigraphy). The outcrop covers a 1.25 by 2.5 kilometre area on Big Interior Mountain, 53 kilometres southwest of Comox.

The limestone is bounded to the west and north by granodiorite and quartz diorite of the Early to Middle Jurassic Island Intrusions and partially overlain to the south by pillowed basalts of the Upper Triassic Karmutsen Formation (Vancouver Group). The limestone strikes 092 degrees and dips 40 degrees south. Basaltic dykes and sills intrude the limestone. The deposit is comprised of light grey to white recrystallized limestone containing abundant crinoids, corals and brachiopods, and dark grey to white chert.