The region in which the Eva prospect occurs is underlain by mainly sedimentary rocks of the Upper Triassic Tyaughton Group, intruded by felsic rocks of the Jurassic to Tertiary Coast Plutonic Complex.

The Eva showing itself occurs within a sequence of polymictic conglomerate, sandstone and siltstone cut by a swarm of feldspar porphyry dykes. The sedimentary rocks contain patchy skarn alteration consisting of the mineral assemblage calcite-diopside- epidote-quartz-chlorite-vesuvianite-pyrite-hematite associated with abundant calcite veinlets. The pyrite forms ubiquitous stringers, blebs and disseminations. The relationship between skarn alteration and gold-sulphide mineralization is unclear.

The main vein comprises calcite, quartz, pyrite, bismuthinite, stibnite, arsenopyrite, specular hematite and minor chalcopyrite, with the stibnite occurring as disseminations and massive bands. Outcrop of the vein contains up to 6.51 grams per tonne over 0.23 metre (Assessment Report 18056).

One hundred and twenty metres to the northwest of the main vein, a 1986 drill hole intersected a 1.2-metre wide shear zone with quartz veinlets and disseminated pyrite, stibnite and arsenopyrite within a steeply dipping feldspar porphyry dyke striking at about 145 degrees. This zone contained 1.7 grams per tonne gold.