The A occurrence is located approximately in the centre of the A 1 to 20 claim group, immediately east of the northern limit of the Kwadacha Wilderness Provincial Park, 23 kilometres southwest of the Tuchodi Lakes, in the mountainous Muskwa Ranges of the Northern Rocky Mountains (Claim map; Geology, Exploration and Mining in British Columbia 1972, page 490).

The occurrence is in a region known as the Muskwa Anticlinorium, a major north-northwest trending structure characterized by thrust faulting and moderate folding. The structure consists of Middle Proterozoic (Helikian) rocks called the Muskwa Assemblage, as well as Paleozoic rocks (Geological Survey of Canada Map 1343A; Geological Society of America, Geology of North America, Volume G-2, pages 111, 639). All belong to Ancestral North America (Geological Survey of Canada Map 1713A). Northwest-striking diabase and gabbro dykes are common in the region.

Few geological details are available for the A occurrence. From its location, the claim group is underlain mainly by conglomerate, sandstone and minor limestone of the Lower Cambrian Atan Group (Geological Survey of Canada Memoir 373, Map 1343A), although the main reference mentions only dolostone (Geology, Exploration and Mining in British Columbia 1972). To the east and unconformably beneath the Cambrian rocks are argillite and quartzite of the Aida Formation of the Muskwa Assemblage. Regionally, strata strike north-northwest and dip gently to moderately west.

Galena and sphalerite are reported to occur in both of the above units, but the nature of the mineralization is not documented (Geology, Exploration and Mining in British Columbia 1972). In the region generally, lead-zinc mineralization usually occurs in quartz veins in carbonate rocks.