The Lone Chasm occurrence is located at an elevation of approximately 1400 metres on a small south east flowing creek, referred to as Lone Chasm Creek, in the north western head waters of the Thautil River.

The area is underlain by Lower Jurassic Telkwa Formation (Hazelton Group) andesitic flows, tuffs and breccias which have been intruded by a Late Cretaceous quartz monzonite porphyry stock of the Bulkley Plutnonic Suite.

Locally, an oxidized zone associated with felsic dikes intruding an andesite on the north western margin of the MSJ stock hosts undescribed copper-silver mineralization. The mineralization is reported to be similar to that of the nearby MSJ occurrence and comprise quartz-sericite-pyrite (phyllic) alteration with associated pyrite-chalcopyrite mineralization.

In 2008, two chip samples (14567 and 14568) yielded 4.03 and 4.28 per cent copper with 146 and 51.9 grams per tonne silver over 2.0 and 0.7 metres, respectively (Pautler, J. (2009-07-15): Technical Report on the El Toro Project).

The area has been explored in conjunction with the nearby MSJ (MINFILE 093L 241) occurrence and a full exploration/work history can be found there.