The Tin City showings are located at about 730 metres elevation, a few hundred metres north of where Cockle Creek empties into Duncan Lake.
The Dary and Dismuth claims (082KNE062), located on the north side of Cockle (Bear) Creek canyon (1463 metres elevation), were owned in 1920s by the Tapanila family of Kaslo. The workings included two inclined shafts about 90 metres apart on the Dismuth claim. In 1945, five contiguous claims were staked by R.E. Erdahl and J.E. Pinchbeck in the vicinity of lower Cockle Creek on a northwesterly trend. They were known as the Tin City, Canyon, Old Glory, Cyclone and Erbeck (082KNE016) claims. The Tin City was staked to cover a showing of tin, beryllium and scheelite mineralization. Claims in the vicinity of the Erbeck claim were Crown-granted in about 1900 (Iron Hand (Lot 5668) and Iron Chief (Lot 5669)). Sipald Resources acquired 12 claims covering much of the area in 1983. Newmont Exploration of Canada Limited optioned the property in 1984. Work by Newmont in 1984-85 included geochemical soil, silt and rock chip surveys, a magnetometer survey, trenching and 794 metres of diamond drilling in 13 holes.
The area is underlain by coarse clastic rocks of the Upper Proterozoic Horsethief Creek Group. The rocks in the area have been mapped as amphibolite, dolomitic limestone, marble, quartzite and muscovite schist. The amphibolite is possibly a meta-volcanic rock.
The rocks in the showing area as described in the Minister of Mines Annual Report for 1945 are schist, gneiss, limestone and quartzite. Narrow discontinuous and irregular veins stringers and lenses of glassy quartz contain varying amounts of dark tourmaline, mica, amphibole and carbonate. Scattered grains of scheelite occur in many veins and sulphides are present in local concentrations. Traces of tin and beryllium were detected by spectrographic analysis, the estimates for both elements ranging up to 0.04 per cent (Minister of Mines Annual Report 1945, page 107).
Newmont discussed the showings after their 1984 work as follows. A skarn-altered tourmalinized rock is associated with the limestone-amphibolite contact cutting across the Tin City area. A thin section of the rock taken by Newmont confirmed it to be a tourmaline-rich muscovite-fluorite skarn or tourmalinite. Hand specimens show fine to coarse scheelite throughout the matrix. One sample assayed 1.12 per cent tungstic oxide (WO3) over 2 metres (Assessment Report 13473). Very fine to coarse-grained scheelite occurs in widely-spaced, fracture-related, quartz-feldspar-tourmaline veinlets, principally found in the amphibolite unit.
North about 500 meters is Newmont's Main showing where masses of fine to coarse scheelite crystals are disseminated throughout the skarn matrix. Assays taken over widths of 1 metre range from 0.173 to 0.672 per cent WO3 (Assessment Report 13473). The corresponding tin values were between 15 and 45 parts per million. Minor galena was noted in place.