The country rock in the area of the Silver Coin occurrence is Triassic Texas Creek Granodiorite, which regionally underlies and locally intrudes pelitic metasedimentary and subordinate andesitic metavolcanic strata of the Jurassic or older Mesozoic Hazelton Group; and the Eocene Hyder Quartz Monzonite, which intrudes the Hazelton and Texas Creek rocks (Smith, 1977; Koch, 1996).

Buddington (1925, p. 90; 1929, p. 95) describes the deposit as a quartz fissure vein up to about 10 feet thick and 50 feet long in a shear zone in granodiorite. The northern 25 feet of the vein contains a shoot as much as 5 feet thick of massive galena, accompanied by a little pyrite and chalcopyrite. The remainder of the vein is barren. A little malachite occurs on shear surfaces in the granodiorite footwall of the ore shoot.