GEOLOGY

The Ruby Hill Mine is located along the southeastern end of the Battle Mountain/Eureka gold trend. The Eureka District exposes a nearly continuous sequence of Cambrian and Ordovician carbonate units with subordinate shale and quartz sandstone. Polymetallic base metal deposits of Cretaceous age are located throughout the district and were some of the first deposits mined in the late 1800’s. The Blackjack target at Ruby Hill is a Cretaceous skarn deposit located on the margin of the Graveyard Flats stock. Mineralization at Blackjack is composed of coarse grained pyrite, sphalerite, and argentiferous-galena. During the 1990’s Homestake Mining Company discovered an oxidized Eocene Carlin-type ore body in the Goodwin Formation, with what would become the Archimedes pit. Later discoveries included the Ruby Deeps deposit characterized by Carlin-type sulphide breccias in the Windfall limestone and Dunderberg Shale. Like other Carlin-type systems gold at Archimedes and Ruby Deeps is located in the rims of arsenian-pyrite around pre-existing pyrite grains and is associated with silicification and decarbonatization.