The GB property occurs within the Stirrup Creek epithermal district, located about 35 kilometres to the southeast of the Blackdome epithermal deposits.

The GB showing is underlain by sedimentary rocks of the Lower Cretaceous Jackass Mountain Group comprising sandstone, argillite and, elsewhere in the area, conglomerate. Intruding the sedimentary succession is a quartz feldspar porphyry body containing disseminated pyrite, galena, sphalerite, stibnite and realgar.