The Oro claims are underlain by Hurley Formation rocks of the Upper Triassic Cadwallader Group, consisting of sediments and volcanic aquagene breccia striking northwest and dipping southwest. These are intruded by quartz diorite stocks and hornblende porphyry dykes of the Jurassic to Tertiary Coast Plutonic Complex.

On the Oro 3 claim, three narrow quartz-calcite veins containing minor disseminated pyrite, chalcopyrite and stibnite occur in a quartz diorite stock near the contact with Hurley sediments and volcanics. The veins average 30 centimetres in width, strike north-northwest and dip steeply west.

Grab samples assayed 12.0 grams gold per tonne and 97.4 grams silver per tonne (Assessment Report 14725). The original "stibnite" showing (on Oro 2) is hosted in Hurley volcanics and sediments near a hornblende porphyry dyke. Narrow veins in shears are 60 metres long by 25 centimetres wide and contain an average of 8.9 per cent antimony. Northeast of the original showing, also on the Oro 2 claim, 2 narrow stibnite-quartz-calcite veins are hosted in quartz diorite near a felsite dyke. The veins strike north-northwest, dip steeply north and average 7.5 per cent antimony over 25 centimetres for 15 metres strike length. One grab sample assayed 16.9 per cent antimony (Assessment Report 14725).