The Dora-Mabel occurrence is located between Kelvin and Humes creeks, approximately 2.3 kilometres north of the Koksilah River.

The area is underlain predominantly by bedded chert and cherty basaltic tuffs of the Mississippian to Pennsylvanian Fourth Lake Formation (formerly the Sediment-Sill Unit of Muller), Buttle Lake Group. These are overlain by limestone, bedded chert and cherty tuff of the Upper Pennsylvanian to Lower Permian Mount Mark Formation, Buttle Lake Group (formerly the Buttle Lake Formation). Between the Mount Mark and Fourth Lake formations, and above the Mount Mark Formation, are packages of mainly basaltic rock, of unknown affinity. These Paleozoic rocks are intruded by numerous dykes of feldspar porphyritic dacite and rhyolite and part of a granodioritic stock of the Early to Middle Jurassic Island Plutonic Suite (formerly known as the Island Intrusions).

Very strongly fractured gossanous intrusive rocks are exposed, including rhyolite, porphyr- itic dacite and granodiorite. The intrusives contain shear-bounded inclusions, 2 to 7 metres wide, of chert, skarn and marble and are in contact to the south with chert and interlayered skarn of the Mount Mark Formation. The skarns and the intrusives contain abundant fracture pyrite; the rhyolite commonly contains 3 to 5 per cent disseminated pyrite and locally, narrow zones of strong epidote alteration with 5 to 15 per cent pyrite. The only massive mineralization exposed consists of a lens(?), up to 50 centimetres in width, consisting of magnetite and 1 to 2 per cent chalcopyrite.

The Dora-Mabel skarn showing has been explored, since 1903, by 4 adits and is well exposed on the surface by roadcuts. In 1983 through 1985, Reward Resources completed programs of prospecting, geochemical sampling and ground geophysical surveys on the Independence, Koksilah, Pacific Star and Western mineral claims. A chip sample across the magnetite lens graded 0.97 per cent copper and 4 grams per tonne silver. A grab sample of chlorite altered basalt with 10 per cent chalcopyrite from an outcrop of epidote altered rhyolite yielded values of greater than 40,000 parts per million copper and 3.4 grams per tonne silver (Assessment Report 13997).

In 1986, Hollycroft and Nexus resources completed a program of geological mapping and rock sampling on the Sil claims.