Two northwest trending arches with exposed Jurassic marine sediments and Cretaceous lithic and quartz-lithic tuff units dominate the local geology. The arches have been intruded by at least three stages of dikes and small stocks, ranging in composition from andesite to latite and rhyolite. Marginal to the northwest trending arches, andesitic volcanic flows and flow breccias have been deposited in at least three west-northwest trending basins. Dikes of andesite and latite crosscut the andesite flow package.
The mineralized zones display a combination of fissure vein, stockwork, and breccia morphologies that change rapidly on strike and dip. The zones range in width from less than one metre to composite vein/stockwork/breccia zones up to 15 metres wide. In the Diluvio zone, gold and silver-bearing vein/stockwork zones locally attain thicknesses in excess of 100 metres. Length of individual veins varies from 100 metres to over 3 kilometres. Property-wide, gold-silver-bearing veins occur over a vertical range greater than 600 metres.
Mineralogical studies identified opaque minerals, including iron oxides, pyrite, gold, electrum, stibnite, and rare pyrargyrite, within a gangue of substantial chalcedony, quartz, and carbonate.