The For 40 occurrence is located 750 metres south of Marble River, approximately 2 kilometres south east of the river mouth on Varney Bay.

The region is underlain by northwest trending volcanics and sediments of the Upper Triassic Vancouver Group (Karmutsen, Quatsino, and Parson Bay formations).

Locally, traces of tetrahedrite and malachite are present in an outcrop of Quatsino Formation limestone. The limestone strikes 305 degrees, dipping 30 degrees south. Amygdaloidal andesite of the Karmutsen Formation is located to the northeast, across the river. The amygdules are filled with chlorite and quartz.

In 1968, Forrest Kerr Mines completed a program geological mapping and soil sampling on the area as the Bill and For claims.