North trending quartz veins on Granville Mountain are thought to be genetically related to the intrusion of Eocene Coryell syenites into Carboniferous to Permian Mount Roberts Formation metasediments and Middle Jurassic quartz monzonites. Gold-bearing quartz vein systems occur within the quartz monzonite and average 1.2 metres thick. The north trending veins are generally steeply dipping to the east and are subparallel
to two major joint orientations.
In the East St. Thomas showing area, Middle Jurassic granitic rocks intrude volcanics, limestones and greenstones of the Mount Roberts Formation. These are cut by porphyritic syenites of the Coryell Plutonic Suite. Skarn-related mineralization contains minor gold and silver values. The skarn showings are often silicified and typically contain garnet, epidote, pyroxene, minor potassium feldspar and graphite. Magnetite and pyrite occur locally.
A 20-centimetre sample of the East St. Thomas v
ein assayed 1.4 grams per tonne gold and 0.01 per cent copper; and 450 metres to the southeast an 80-centimetre sample from the Magnetite adit assayed 7.5 grams per tonne gold, 7.9 grams per tonne silver and 0.24 per cent lead (Assessment Report 14733). Sulphides in the quartz veins consist of chalcopyrite and galena.
Prominent Resources Corporation conducted surveys and sampling in 1985. In 1992, Crown Resources Corp. conducted airborne geophysics, ground magnetometry, soil sampling, rock chip sampling and reverse circulation