The Melvin occurrence is located just northeast of the Prosperity and Porter Idaho mines (103P 089), 5 kilometres southeast of Stewart. Prospecting adjacent to the mine in 1928 revealed several narrow shear zones carrying high silver values.

The occurrence consists of a shear zone striking 160 degrees and dipping steeply west, hosted in plagioclase porphyritic andesite of the Lower Jurassic Unuk River Formation (Hazelton Group). The zone contains blocks of andesite in a white quartz matrix. A 0.1 to 0.66 metre wide sulphide-rich zone along the footwall of the shear zone contains abundant coarsely crystalline galena and sphalerite, some pyrite, chalcopyrite and trace native silver. A 1.0 metre chip sample taken from the adit assayed 0.031 gram per tonne gold, 72.15 grams per tonne silver, 0.15 per cent lead and 0.46 per cent zinc (Assessment Report 8650, page 10).

A second 0.3 metre wide shear zone, in the same vicinity, contains a 0.15 metre wide sulphidic lens. A 0.10 metre chip sample across the lens assayed 24,000 grams per tonne silver (Minister of Mines Annual Report 1928, page 25).

In 1929, four tonnes of ore were mined from the main zone with an average grade of 6642 grams per tonne silver.

In 1929, the main working consisted of a drift which had been driven for 12 metres on a high-grade stringer in a shear zone. A winze was started at a point about 6 metres in from the tunnel portal, which at the time (ca. 1929) was down 2.1 metres. A width of 66 centimetres of well mineralized vein matter was exposed in the bottom and some more left on the hangingwall.