The Castor Fraction occurrence is located 2.5 kilometres west of the summit of Mount Wallace and 2.0 kilometres south-southeast of Beaverdell, British Columbia (Assessment Report 16772).
Initial prospecting began in the Beaverdell area in the late 1880s. The first ore was shipped in 1896. The major producing mines in the Beaverdell silver-lead-zinc vein camp, from west to east, were the Wellington (082ESW072), Sally and Rob Roy (082ESW073), Beaver (082ESW040), and Bell (082ESW030), with numerous other small workings throughout the area. The Castor Fraction claim was first Crown granted to Victoria and Boundary Creek Development and Mining Co. Ltd. in 1911. In 1918, the property was leased to R. Perry and associates. Ore shipments were made from 1919 to 1922 from 76 metres of tunnel. In 1925, it was amalgamated with the Sally claim group, consisting of the Sally Fraction, Nodaway, Duncan, Excelsior, Sally, Kid Fraction, Highland Queen, Alice M. Fraction, Hard Times Fraction, Tunnel Fraction, Rob Roy, Pueblo Fraction and Castor Fraction. By 1949, the property became part of the ground held by Highland-Bell Ltd., owner of the Highland-Bell (Beaverdell) mine. The Highland-Bell mine produced until 1991. The Castor Fraction (Lot 2278) adjoins the Tiger claim (082ESW067) in the northeast, the Bounty claim (082ESW033) in the southeast, the Bounty Fraction claim (082ESW066) in the south, the Duncan claim (082ESW032) in the west and the Kokomo Fraction claim (082ESW031) in the north. The property is underlain by Westkettle granodiorite.
Mineralized quartz veins and veinlets occur in a east trending shear zone. A pre-mineral andesite dike (Wellington-type) occupies the same structural zone and parallels the veins. A syn or post-mineral quartz latite dike (Idaho-type) also occurs. The zone hosting the quartz veining is highly faulted and fractured.
Mineralization consists of pyrite, galena, sphalerite and native silver in a gangue of mainly quartz. Some hematite is also present as an oxidation product. A 0.6-metre drill core sample taken in 1986 during property exploration by Teck Corp. yielded 626.6 grams per tonne silver and 0.68 gram per tonne gold (Assessment Report 15704).
The Castor Fraction occurrence has produced 70 tonnes of ore between 1919 and 1922. Recovery totalled 522,717 grams of silver, 62 grams of gold and 1974 kilograms of lead.
For a detailed description of the geology and mineralization of the area refer to the Beaverdell (082ESW030).