The area of the Empire showing is underlain mainly by Eocene and younger volcanics comprising rhyolitic and dacitic tuff, breccia and flows, and minor andesite and basalt. Also occurring in the area are Oligocene and Lower Miocene porphyritic and amygdaloidal andesite and basalt tuff, breccia and flows.

Agate, "thundereggs" and perlite occur on the property of Empire Valley ranch and beyond. Stringers and nodules of chalcedony are contained in a mafic volcanic porphyry underlying the perlite. The quality is apparently good. Opal and jasper are also reported to occur.