The River area is underlain by a sequence of folded and faulted upper Triassic andesitic volcanic and clastic sedimentary rock units of the Stuhini Group. The sequences of clastic layered rocks consist of volcanic wackes, andesitic flows, and argillite interbeds.

The River vein, originally discovered by Tungco Resources in 1987, is a 2 to 25 centimetre wide quartz-chlorite vein containing pyrite, magnetite, and chalcopyrite. It was reported to be oriented at 140 to 150 degrees/45 to 90 degree southwest, exposed for 50 metres and hosted by volcanic agglomerate. Two grab samples collected from the River Vein in 1987 assayed 36.79 and 3.77 grams per tonne gold (Assessment Report 18113). Thirteen samples collected south of the vein area, contained values ranging from 1.16 grams per tonne to 4.62 grams per tonne gold but across very narrow widths (Assessment Report 18113).

Investigations in 1990 by Big M Resources revealed sheared and locally gossanous quartz veins which carry 5 to 7 per cent pyrite, 1 to 5 per cent magnetite, and trace to 3 per cent chalcopyrite. The mineralization is generally found in the form of small lenses of semi-massive to massive sulphides. At one point, it reaches a width of 35 centimeters and contains 2 quartz veins, 4 and 6 centimetres wide. The main showing exposed the structure for a 5-metre strike length. Along strike to the southeast, a narrow, 1 to 2 centimetres wide, quartz vein with minor pyrite and magnetite is present. Chip samples collected from the main structure revealed very erratic gold values along strike. The chip samples taken across the exposure to the southeast yielded only anomalous gold values.

Refer to Gold Bug (MINFILE 104B 295) for details of a common work history.