The Lost claim was centered on an outlier of Paleozoic strata surrounded by upper Proterozoic metasedimentary rocks of the Horsethief Group. The outlier consists of a northwest trending package of dolomitic carbonate rocks of the Ordovician to Silurian Beaverfoot Formation overlain by rocks of the Devonian Mount Forster Formation comprising limestone, slate, siltstone and argillite.

The Lost claim was staked in 1980 to cover anomalous base metal concentrations in stream sediments. During staking, sparse galena was observed in fractures in dolostone float collected near the northeast corner of the claim. Subsequently, the probable source of the floated was located in outcrop. Samples of highly oxidized galena and sphalerite were collected from a number of widely-spaced, vertical fracture/breccia zones, up to 1.2 metres wide, in dolomitic carbonate. The samples contained up to 12 per cent lead, 31 per cent zinc and 309.15 grams per tonne silver (Assessment Report 8842).