The area of the Randeb 3 showing is underlain by mainly quartz-sericite-biotite gneiss and associated lenses of metavolcanic and ultramafic rocks. These rocks are part of the Custer Gneiss, a metamorphic package probably derived from lower Mesozoic and possibly Paleozoic and Precambrian rocks and metamorphosed in the Late Cretaceous and early Tertiary.

A showing, some 3 metres in width, of ultramafic rock is reported to have assays similar to that of Randeb 2 (092HSW120). Randeb 2 yielded values high in silver and nickel and especially high in gold (1.5 grams per tonne).