Both have been age dated at Eocene. The deposit occurs in a triangular zone of disseminated and veinlet copper sulfide mineralization 1.5 x 2.5 km in plan and at least 500 meters in thickness. The majority of the ore is in the granodiorite, but substantial reserves are present in the metamorphosed Paleozoics. The original host intrusive was a granodiorite, but subsequent hydrothermal alteration has resulted in a rock more closely approximating a granite. The stock has a well defined potassic alteration zone characterized by secondary biotite, poorly defined phyllic alteration and a spotty and irregular propylitic alteration zone.
Argillic alteration is absent.
Extensive brecciation of both the intrusive and country rock is common. The core of the intrusive is moly rich with pyrite abundant only in the phyllic zone. Chalcopyrite and minor bornite are the only primary copper sulfides recovered. Peripheral skarn deposits consisting of enargite, galena, sphalerite and tetrahedrite are important in the surrounding metasediments. Typical of most American deposits, early mining was from a supergene enrichment zone of chalcocite, malachite and native copper lying beneath a barren limonite cap 10-100 meters thick.