The Velvet occurrence is underlain by Paleozoic serpentinite which forms a huge roof pendant surrounded by syenite of the Middle Eocene Coryell Intrusions. Within the serpentinite are large xenoliths of Rossland Group volcanic rocks, particularly on the Portland claim. The rocks within the pendant are cut by dykes up to 6.0 metres wide, commonly of porphyritic syenite and of medium- grained granodiorite. These dykes are related to the Coryell and Middle to Late Jurassic Nelson intrusions respectively, and in general are parallel with the main shears.

The origin of the copper, gold, silver veins at the Velvet Mine is not well understood. They may be mesothermal structures related to middle Jurassic thrust faults marginal to ophiolitic lithologies; it may be a skarn; it may be that the veins are related to the Middle Eocene Coryell Intrusions (EMPR Bulletin 109, page 48).

The mineralization occurs in replacement veins that strike north and dip steeply to the west. Besides the main or Velvet vein, four other veins are known to exist in its footwall some 18, 40, 58 and 98 metres to the east, respectively. A few small, relatively short east-west striking veins cut the main vein. Ore shoots occur at intersections of the main vein with crosscutting dykes or faults. Mineralization includes specularite, pyrite, chalcopyrite and malachite in a gangue of quartz and calcite. Molybdenite also occurs locally in a gangue of quartz and altered wallrock. Chalcopyrite mineralization is described as typically massive where it occurs along the walls of the ore shoots. Small amounts of scheelite have been seen in the dump and underground workings. As well, lead and zinc were recovered from minor occurrences of galena and sphalerite.

From 1901 to 1964, 88,833 tonnes of ore produced 620,785 grams gold, 664,359 grams silver, 1,154,104 kilograms copper, 37 kilograms lead, and 25 kilograms zinc. In 1982, it was reported that 907 tonnes of ore grading 5.4 grams per tonne gold with other commodities was shipped to the HB mill (082FSW004) of David Minerals Ltd.

The Velvet and Portland Crown-granted claims and several others held by record lie on the northwest slope of Mount Sophia at about 1097 metres elevation. The mine is about 13 kilometres directly southwest of Rossland and 2 kilometres north of the International Boundary.

In April 1896 J. Cromie located the Portland claim and in September of the same year O. Geldness located the Velvet. The two claims were developed separately until 1904. The Velvet claim was acquired in 1897 by Velvet Mines Ltd. and they carried on development work until Velvet-Portland Mines Ltd. was formed in 1904 to acquire both properties. The mine was operated intermittently by the company or by leasers until it was closed in 1916. Granby Consolidated Mining, Smelting & Producing Co. examined the workings in 1918 and subsequently relinquished their option.

Rossland-Velvet Mines Ltd. took over the property in 1920 and intermittent work was carried on by the company or by leasers until 1928 when the mine closed. Velvet Gold Mining Co. Ltd., formed in the fall of 1932 reopened the mine and operated it intermittently until the fall of 1937.

Velgo Mining Incorporated took over the property in 1938 and later in the year leased it to R. Bielli & Associates who subsequently formed the Velvet Leasing Syndicate; the syndicate name was changed in 1941 to Velvet Gold Leasers. The leasers operated until 1942 when the mine was closed. The mine remained closed until 1952 except for a brief period in 1946 when Velvet Gold-Copper Mines Incorporated acquired the property and leased it to J. Coryell, Jr. A diamond drilling program was carried out at this time consisting of 7 holes totalling 438 metres from No. 8 level and 4 holes totalling 172 metres from the surface.

In 1952 the property was acquired by Messrs. Kenward and Sweet. Leasers began mining operations and in 1953 built a small mill. Mid-West Copper & Uranium Mines Ltd. acquired the property in 1955 and intermittent operations were carried on by the company or by leasers. A new mill was built and put into operation in 1956. In October 1964 the company was reorganized under the name Mid-West Mines Ltd. The property is developed by a vertical shaft serving 6 levels, of which No. 4 and No. 6 are accessible from the surface by adits. A 527-metre long adit on No. 8 level is connected to No. 6 level by a raise. Around 1978, Velvet Exploration Co. Ltd. (formerly Kendal Mining and Exploration Company Limited) acquired the mine. In 1980, they carried out 914.4 metres of drilling of which 244 metres was diamond drilling, the rest was percussion. In August 1982 it was reported that 1,000 tons grading 5.48 grams per tonne gold and other commodities were shipped to the H.B. mill of David Minerals Ltd. in Salmo.

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. Single point gold anomalies ranged from 105 parts per billion to 2647 parts per billion (Simmons, B. (2007-06-08): Report on the Portland Project). Copper anomalies correlated closely to gold anomalies. Overall, a 300 by 200 metre metal signature anomaly was identified with gold values ranging from 113 parts per billion to 2035 parts per billion and silver values up to 4.1 parts per million (Simmons, B. (2007-06-08): Report on the Portland Project).