The Douglas Crown-granted claim is located on the west side of Mount Sophia adjacent to the International Boundary and about 1.6 kilometres south of the Velvet mine from which it in accessible by road.

The earliest development of the Mine was in 1900 and 1901 when some 240 metres of tunnelling was done. No further activity was reported until the period from 1948 to 1950 when the Present owners did some development work and made a small shipment of ore.

The workings consist of 3 adits at elevations of approximately 1204, 1237 and 1274 metres. In 1949, when the property was examined by Little, the middle adit was caved and the upper adit accessible for only a short distance.

The Douglas Crown grant is underlain by coarse conglomerate of the Upper Cretaceous Sophie Mountain Formation in which lenticular beds of coarse-grained faintly stratified sandstone and argillite strike 340 degrees and dip 70 degrees northeast. The conglomerate is cut by several dykes of the Middle Eocene Coryell Intrusions comprised of pink to greenish porphyritic syenite as well as sheared lamprophyre dykes exposed in the underground workings.

A shear zone, striking 120 degrees and dipping 70 degrees northeast, exists along the contact between the conglomerate and syenite. The shear zone is approximately 3.0 metres wide and hosts individual mineralized lenses and veins of quartz ranging up to 0.3 metre in width. They occur in irregular intervals along the lower tunnel of the 230-metre long underground workings. The quartz veins are locally fractured, and the fractures filled with altered wallrock. Pyrite is the most abundant mineral with occasional concentrations of galena, sphalerite and chalcopyrite.

In 1948 and 1950, a total of 9 tonnes of quartz-rich ore was shipped and produced 591 grams silver, 592 kilograms lead, and 479 kilograms zinc.

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.