The Marion C showing is within the historic King William camp, situated on Mineral Hill, approximately 7.5 kilometres southwest of the community of Stump Lake.

The occurrence is hosted within a north-trending belt of Upper Triassic intermediate volcanics, volcaniclastics and sediments belonging to the Nicola Group. The greenstones consist primarily of massive, chlorite-epidote altered andesite and basalt, augite porphyry, andesitic flow breccia and tuff, with minor interbedded argillite, conglomerate, and limestone. Attitudes of tuff horizons and sedimentary bedding suggest that a north plunging axis of a syncline passes through Mineral Hill. Nicola Group rocks in the region are intruded by Lower Jurassic granitic batholiths both west and northeast of Stump Lake, and scattered granodiorite outcrops have been mapped near the camp.

The area is structurally complex, with numerous subsidiary faults associated with the north- to northeast-trending Quilchena and Stump Lake regional fault systems. These fractures appear to have controlled both hydrothermal alteration and mineralization. Andesitic host rocks exhibit widespread bleaching, silicification, pyritization, and brecciation. Mineralization is hosted mainly in quartz veins, and less commonly calcite veins, which generally strike northward and dip steeply to the east (Assessment Report 41373).

The Marion C showing is interpreted as the southernmost extension of the King William vein system (MINFILE 092ISE110). Mineralization is exposed in historic open cuts, where a quartz vein approximately 10 centimetres wide is hosted by altered andesite. The vein contains minor pyrite, galena, sphalerite, and chalcopyrite. A chert unit occurs nearby, with bedding striking approximately 010 degrees and dipping 50 degrees west. Grab samples collected from the vein returned assays of 17.82 grams per tonne silver, 0.09 per cent lead, 0.03 per cent zinc, 0.01 per cent copper, and 0.10 grams per tonne gold (Assessment Report 5152).