The Middle D occurrence is located at an elevation of approximately 1200 metres on a gently northeast-facing slope, west of Marble Creek and approximately 2 kilometres southeast of the town site of Cassiar.

Regionally, the area is underlain by quartz arenite sedimentary rocks of the Lower Cambrian Boya Formation (Atan Group), limestone, marble and calcareous sedimentary rocks of the Lower Cambrian Rosella Formation (Atan Group), limestone, slate, siltstone and argillite of the Ordovician to Silurian Road River Group, calcareous sedimentary rocks of the McDame Group, fine clastic sedimentary rocks of the Upper Devonian to Lower Mississippian Earn Group and basaltic volcanic rocks of the Mississippian Slide Mountain Complex. Granitic intrusive rocks of the Lower Cretaceous Cassiar Batholith are exposed to the west.

Locally, silver-lead-zinc mineralization is emplaced as irregular east-trending replacement shoots within carbonates of the Lower Cambrian Rosella Formation (Atan Group), adjacent to the north-trending Marble Creek fault. Locally, the replacement bodies are conformable. The limestone host has been extensively dolomitized in association with mineral emplacement. Galena with a silver-lead ratio of approximately 1:1 and sphalerite comprise the bulk mineralogy. Gangue material is siderite, carbonate, tremolite and silica with varying quantities of pyrolusite, pyrrhotite, pyrite and magnetite. The shoots vary in thickness from several centimetres up to 7 metres. Drilling has tested the deposit to a vertical depth of 90 metres.

In 1979, drill-indicated reserves were reported at 90,000 tonnes grading 6.3 per cent zinc, 3.3 per cent lead, and 70 grams per tonne silver (Assessment Report 7912).

In 1998, a grab sample (98/08/05/ZN) of float hosting pyrite-pyrrhotite from a historical trench assayed 2.9 grams per tonne gold (Assessment Report 25889).

In 2002, samples of arsenopyrite-bearing boulders yielded up to 6.2 grams per tonne gold and 0.5 per cent tin (Sample 7700; Assessment Report 27203).

Work History

In 1969, Chapparal Mines Ltd. and Coast Silver Mines Ltd. completed a 486.0 line-kilometre airborne magnetic survey on the area.

In 1979 and 1980, Shell Canada Resources Limited conducted an exploration program directed toward evaluating the tin potential of known showings and to outline favourable areas for additional mineralization. The property was geologically mapped and sampled, approximately 66 line-kilometres were cut in three grids over which magnetic, induced polarization and shoot-back electromagnetic surveys were run and a reconnaissance geochemical survey completed. Approximately 600 metres of diamond drilling was completed in seven holes. Five holes were drilled to test the Granite Creek (MINFILE 104P 081) occurrence, and other isolated geophysical anomalies previously untested.

In 1996, Pacific Bay Minerals conducted an exploration program, which consisted of prospecting, grid-controlled soil sampling and 270 metres of reverse circulation drilling in one hole. A total of 9 rock grab samples, 444 soil samples, 14 panned samples and 15 stream silt samples were taken. During 1998 through 2008, Eveready Resources Corporation completed programs of geological mapping, geochemical (rock and soil) sampling and trenching on the area as the Cassiar property. In 2014, BC Moly Ltd. completed a program of geological mapping on the Storie property.