Exploration and Development
development require the careful extraction of rock samples to determine ore *******. When a site is identified as containing significant ore *******, it is prepared for mining.
Rocks are blasted to break them into smaller pieces and loaded into large trucks for transport to one of two processing locations. Where the ore goes either to concentrating and smelting, or to leaching and electrowinning depends on how much copper and the types of minerals it contains. Development rock is the material that must be excavated to access the ore.
In one copper production process, rock that comes from the mine is crushed into smaller and smaller pieces by heavy steel balls in machinery called mills.
Ground up rock is mixed with water, air bubbles and small amounts of chemicals. The chemicals allow copper minerals to rise to the top and stick to floating air bubbles. The remaining mixture of crushed rock and water called tailing separates from the copper bearing bubbles. The copper minerals are skimmed off and dried to form copper concentrate, a powder-like material.
In the smelter, copper concentrate is melted and copper is separated from other substances in the concentrate. Molten copper is poured into molds called anodes. The unwanted material cools to a glass-like substance called slag. The natural metals that remain in slag are reported under EPCRA.
In an alternate copper production process, rock is taken from the mine directly to stockpiles. A solution of slightly acidic water is dripped on the stockpiles, percolating down through the rock and dissolving copper along the way. The solution containing the copper is collected and piped to holding ponds.
Solution Extraction and Electrowinning
In tanks, the copper-bearing solution is mixed with chemicals that transfer the copper to a more concentrated solution called electrolyte. The electrolyte is pumped to steel tanks. Starter sheets hang in the solution and, using an electric current, the copper is plated from the electrolyte on to the sheet, forming a 99.99 percent pure copper plates. All solutions used during this
process are recycled.