The Montana occurrence is located on the north side of the Marmot River, 9 kilometres east of the Portland Canal and 11 kilometres southeast of Stewart.
The area is underlain by three distinct rock types, represented by the Lower Jurassic Unuk River Member of the Betty Creek Formation, the Middle to Upper Jurassic John Peaks Member of the Salmon River Formation, and the Bulldog Creek pluton. The Betty Creek and Salmon River Formations are part of the Hazelton Group.
The showing is comprised of at least two well-mineralized structures in granodiorite, the Montana vein and a second unnamed vein 350 metres northwest of the Montana vein. The Montana vein strikes 040 degrees for at least 300 metres, dips 25 degrees northwest and varies up to 1.8 metres wide. Mineralization consists of massive lenses and disseminations of sphalerite with lesser pyrite, chalcopyrite, galena and tetrahedrite in a gangue of quartz. A grab sample assayed 0.684 gram per tonne gold, 225.8 grams per tonne silver, 0.585 per cent copper, 4.99 per cent zinc and 0.90 per cent lead (Assessment Report 11943, page 15).
The second unnamed structure consists of a 0.10 to 0.30 metre wide discontinuous lenticular vein of massive galena and sphalerite that initially extends for 7.6 metres along the eastern contact of a vertically dipping andesitic dike striking 050 degrees. The vein continues another 3.6 metres for about 7.6 metres further to the northeast. A grab sample assayed 2.43 grams per tonne gold, 9145.1 grams per tonne silver, 0.785 per cent copper, 11.50 per cent lead and 24.90 per cent zinc (Assessment Report 11943, page 15).
Past production from these veins totals 24 tonnes with an average grade of 7.75 grams per tonne gold, 6075.4 grams per tonne silver, 0.25 per cent copper, 14.14 per cent lead and 19.76 per cent zinc. At least 19 tonnes of this production came from the Montana vein.
The property was worked from 1913 to 1927 during which time numerous tunnels and open cuts were made. The Montana tunnel at 716 metres elevation, west of Montana Creek, was driven below a quartz vein containing galena, sphalerite and pyrite. The workings include an 18-metre tunnel, 15 metres of drifting and a 9 by 6 metre shaft. On the east end of the Horseshoe claim (Lot 4975, 103P 102) at 899 metres elevation, a showing of quartz mineralized with pyrrhotite, chalcopyrite and galena gave values up to $20/ton in gold (ca. 1925). The Canyon tunnel southeast of the Montana tunnel was driven 35 metres following a vein outcropping in Montana Creek; no significant mineralization was encountered. At 975 metres elevation west of Montana Creek, a tunnel was driven 55 metres following a mineralized andesite dike contact. Mineralization 10-30 centimetres wide for the first 7.6 metres from the portal consists of massive galena and sphalerite. A second 4.5-metre lens was intersected 15 metres in from the portal. Numerous cuts and a 9-metre tunnel were made in the second limestone block from the summit. A 15-metre tunnel below the northern limestone-greenstone contact intersected a 3.6-metre lens of sphalerite. Since 1927, the property has seen little or no work except for geological mapping by U & D Kretschmar in 1980. In 1983, mapping and prospecting was conducted by Esso Resources Canada Limited.
Granby Gold Inc.'s Marmot property, containing the Montana showing, underwent geological mapping throughout 2013 to 2015. In 2017 the geology was finer tuned by interpretation with regional airborne geophysics and again in 2018 with airborne geophysical survey data. There is no strong geophysical expression of the Montana occurrence (Assessment Report 38124).
