THE MINERAL INDUSTRY OF ARIZONA 105 
 
Douglas, Inspiration Consolidated Copper Co. smelter at Inspiration, Magma
smelter at Superior, and Asarco smelter at Hayden 
—also treated ores on a custom or toll basis. Phelps Dodge Corp., with
smelters at Ajo, Douglas, and Morenci, controlled 57 percent of the total
smelting capacity within the State; Magma Copper Co., with smelters at San
Manuel and Magma, accounted for 13 percent. The smelters operated by Kennecott
Copper Corp. and Asarco at Hayden, and by Inspiration Consolidated Copper
Co. at Inspiration, each accounted for 10 percent. 
 Approximately 2.2 million tons of ore, concentrates, and precipitates was
shipped to smelters in or outside the State. These shipments consisted of
1.9 million tons (87 percent) of concentrates obtained from milling copper
ores; 203,900 tons of direct shipping ores (9 percent); and 76,500 tons (4
percent) of precipitates from leaching ores ' in dumps, in place, in tanks,
and in heaps. 
 
 Leaching.—As companies incorporated the leaching process from a sideline
to that of an integral part of the copper-producing operation, leaching of
low-grade copper ores in mine dumps was expanded. More than 42.3 million
tons of leach material was placed in new or existing dumps. Ultimately leading
to large-scale chemical mining, studies were underway or planned on the use
of nuclear and conventional explosive charges to fracture low grade copper
ore bodies which would be leached. in place by the controlled percolation
of solutions containing catalysts, solvents, and bacteria. 
 As a forerunner of the new mining systems, Ranchers Exploration and Development
Corp. installed a solvent-extractionelectrowinning facility at its Bluebird
mine near Miami, Gila County. The facility was to upgrade copper-bearing
solutions from the heaps by filtration and mixing with a solvent to separate
the copper from acid and water. In the process, the copper is stripped from
solvent with a high-acid solution; the copper and solution are then sent
to the electrowinning units, consisting of cells containing starting sheets
surrounded by circulating copper-and-solution. Electric current passed through
the solution attracts the copper ions to the starting plates. The copper
cathode grows 
to almost 1 inch thick and weighs about 300 pounds. Shipped directly to the
fabricator, the cathodes contained 99.9 percent copper. The plant designed
and constructed by Bechtel Corp. has a daily capacity of 15 tons of copper.

 Kennecott Copper Corp. submitted a proposal, based on a study,9 to the Atomic
Energy Commission for a joint experiment to evaluate the use of nuclear explosives
in fracturing a low-grade copper ore body for subsequent extraction of copper
by in-situ leaching methods. The Safford deposit of Kennecott Copper Corp.,
located about 9 miles northeast of Safford, was suggested as the experiment
site. The experiment was to involve detonating a 20-kiloton nuclear explosive
underground in the oxide part of the deposit to fragment a test zone of copper
ore. (One kiloton is equivalent to 1,000 tons of TNT high explosive.) A pilot
leaching plant, having commercial size equipment, was to be built to leach
and extract copper from broken ore. Collection of sufficient data to evaluate
the experiment was expected to take about 1 year. 
 In May, Kennecott Copper Corp. began constructing a copper silicate ore
plant and auxiliary facilities at Ray. The $35 million project was to include
a 10,000-tonper-day leaching plant and a- sulfuric acid plant to produce
750 tons of acid daily from sulfur dioxide gas generated at the smelter.
The silicate ores were to be crushed in a conventional crushing plant to
minus ' /2 inch, and the sands treated by 10-day vat leaching. Classifier
~limes were to be leached by agitation for 24 hours and then washed; the
copper sulfate solution was combined with the solution from vat leaching,
and the copper recovered by electrolysis. The new plant was designed to increase
the annual copper output at Ray by 24,000 tons. The acid plant, expected
to begin operations in the last quarter of 1968, was to minimize sulfur dioxide
emitted to the atmosphere. Under construction, to replace the existing facility,
was a new cone-type precipitation plant. The old facility, located near the
pit, was removed to extend the pit perimeter. 
 
 
 9Kennecott Copper Corp., U.S. Atomic Energy Commission, U.S. Bureau of Mines,
Lawrence Radiation Laboratory, and with technical assistance of the Oak Ridge
National Laboratory. Sloop. June 1, 1967, 44 pp.