The Ray Mine is a major low-grade, high-tonnage porphyry copper deposit similar to other porphyry copper systems in the Southwestern U.S. and Sonora, Mexico. It is located about 70 miles north of Tucson, Arizona.

The Ray sulfide system is developed in a variety of Precambrian rocks and Laramide intrusives. The bulk of the hypogene sulfides pyrite, chalcopyrite and molybdenite— occur in schist, the Ruin Granite (a quartz monzonite), quartzite and diabase, all Precambrian in age. Diabase is the youngest Precambrian rock and occurs as dikes and sills in all the older “country” rocks; it is the most receptive rock to copper mineralization and hosts the bulk of the ore at Ray. A series of Laramide (late Cretaceous) intermediate to acidic composition dikes and stocks, representing at least 12 different rock types, intruded all the older rocks. All Laramide rock types have been affected by the later Ray hypogene sulfide system and are cut by sulfide veinlets. Post-mineral Oligocene, Miocene and later volcanic and clastic rocks unconformably overlie part of the sulfide body. Major high-angle, northwest-trending normal faults extend through the deposit area, intersected by major northeast trending faults at the north end of the deposit with major deformation occurring before, after and perhaps during intrusion of ore-age dikes and stocks.

Hypogene mineral zoning is concentric, with a central low-grade core characterized by low total sulfides and a high cpy/py ratio. A higher grade zone (the “ore zone”) surrounds the low-grade core and is characterized by higher total sulfides but with a lower cpy/py ratio than the core. The increase in total sulfides continues regularly outward from the low-grade core but with a decreasing cpy/py ratio resulting in an outer high-sulfide, low copper, pyrite halo. Importantly, the center of this zonal pattern does not coincide with that of any of the porphyry stocks. Neither the deposit nor the intense depositassociated alteration coincides with the densest dike swarms and largest plutons of ore age exposed near the economic mineralization. Based on K-Ar dating from hydrothermal and igneous biotites, the alteration halos were developed at the same time as the Granite Mountain Porphyry which outcrops 4 miles S70°W from the orebody. Systematic changes of sulfide content and copper grade are related to rock type changes (quartzose Precambrian rocks, diabase, and Laramide porphyry) in the Ray orebody.

Due to the site’s geography, the vast majority of the mine haulage operation involves lifting material out of the pit to the dumps or crushers (vertical hauls up to 1,800 ft.). The elevation change adds an additional complexity that must be accounted for to support communications, due to its depth.

The Ray Operations consists of a 250,000 ton/day open pit mine with a 30,000 ton/day concentrator, a 103 million pound/year solvent extraction-electrowinning operation, and associated maintenance, warehouse and administrative facilities. Cathode copper produced in the SX-EW operation is shipped to outside customers and the Asarco Amarillo Copper Refinery.

A local railroad, Copper Basin Railway, transports ore from the mine to the Hayden concentrator, concentrate from the Ray concentrator to the smelter, and sulphuric acid from the smelter to the leaching facilities.