The geology in the vicinity of the Riverside occurrence is not well known. The location of the occurrence is placed close to the western boundary of the north-trending Rock Creek graben, within metavolcanic rocks of the Late Paleozoic Wallace Formation (Anarchist Group). A north-northwest trending Eocene fault, located to the immediate east, juxtaposes alkalic Eocene volcanic rocks of the Marron Formation against Wallace Formation metavolcanic rocks to the west. The Wallace Formation is intruded by diorite and granodiorite of the middle Jurassic Nelson plutonic suite.

Mineralization comprises north-northwest trending quartz veins with pyrite, pyrrhotite and chalcopyrite, in "andesite" of the Wallace Formation.