The Sunset occurrence is situated 9 kilometres south of Rossland, within 1 kilometre northwest of Paterson.

The Sunset occurrence is underlain by the Pennsylvanian to Permian Mount Roberts Formation, consisting of interbedded siltstone, argillite, greywacke and limestone units that strike 038 degrees and dip 40 degrees north. These are overlain by Lower Jurassic Elise Formation rocks of the Rossland Group, composed of black siltstone, andesitic flows, tuffs and breccia. The formations are intruded by a Middle Eocene Sheppard leucocratic granite intrusion.

The occurrence consists of discontinuous veins or lenses of quartz, which host argentiferous galena, sphalerite, chalcopyrite and minor pyrite in the metasediments of the Mount Roberts Formation. The lenses occur in steeply dipping fractures that strike east-west and vary in width from several centimetres to a few metres. Mineralized intersections occur in shear zones near or within the margins of the granitic intrusive and limestone contact. Hematite in ore from the New Sunset is partially replaced by magnetite.

In the years between 1898 and 1964, the mine produced a total of 43 tonnes, from which 4448 grams of silver, 373 grams of gold, 1420 kilograms of lead, 1940 kilograms of zinc and 99 kilograms of copper were recovered.

In 1964, Utica Mines Ltd. completed 13 diamond drill holes totalling 853.7 metres. Mineralization consisted of galena, sphalerite and chalcopyrite with elevated silver values (Assessment Report 2161). After Utica dropped their option, property owner Warren Crowe shipped 6.4 tonnes of ore to the Trail smelter, assaying 0.368 gram per tonne silver, 7.1 per cent lead and 23.9 per cent zinc (Minister of Mines and Petroleum Resources Annual Report, 1964).

In 1974, Bow River Resources Ltd. completed a geochemical survey on the property, finding coincident northwest-trending anomalies of copper, lead and zinc postulated to reflect buried mineralized vein systems (Assessment Report 5355).

In 2006, Major Gold Limited conducted a mineral exploration program on the Portland Project. This included prospecting, grid surveys, soil geochemistry, rock sampling, and magnetometer surveys. Results from the soil grid geochemistry survey and the magnetometer survey showed anomalous gold, silver, copper, arsenic, lead, and zinc patterns correlating to known mineralization on the property.