Copper Mining and Processing: Resources and Glossary

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alloy: A material made of two or more metals (such as brass or bronze), or of a metal and another material.

anode: 1. An electrode through which conventional current flows into a polarized electrical device; in electrolysis, it is the positive terminal. 2. In copper processing, a copper anode is an intermediate product from the smelting furnaces which is used as a copper source from which to make copper cathodes during electrolysis.

aqueous: Of or containing water, typically as a solvent or medium; i.e., an aqueous solution.

brass: A yellowish alloy of two-thirds copper and one-third zinc, sometimes including small amounts of other metals.

bronze: A yellowish-brown alloy of two-thirds or more of copper and up to one-third of tin, sometimes including small amounts of other metals.

cathode: 1. An electrode from which conventional current leaves a polarized electrical device; in electrolysis, it is the negative terminal. 2. In copper processing, a copper cathode is the final, 99.99% pure product of the electrolysis process, and is itself the primary raw material input for the production of finished copper products, such as rode, tubes, and wires.

cation: A positively-charged ion that is attracted to the cathode (negative terminal) in electrolysis.

closure: In mining, the period of time when the ore-extracting activities of a mine have ceased, and final decommissioning and mine reclamation are being completed. It is generally associated with reduced employment levels, which can have a significant impact on local economies.

copper: A reddish-brown, ductile, malleable metallic element that is an excellent conductor of heat and electricity and is widely used for electrical wiring.

copper oxide ore: A copper-containing ore that in which some of the original minerals have been oxidized; typically processed with hydrometallurgy. Includes chrysocolla, azurite, malachite, and cuprite. Typically processed using hydrometallurgy.

copper sulfide ore: A copper-containing ore that is typically a mixture of copper carbonate, sulfate, phosphate, and oxide minerals and secondary sulfide minerals. Includes chalcocite and chalcopyrite. Typically processed using pyrometallurgy, although low-grade ores may sometimes use steps from the hydrometallurgy process.

development: In mining, the process of constructing a mining facility and the infrastructure to support it; typically occurs before extraction begins, but can also occur concurrently.

electrode: An electrical conductor, though which a current enters or leaves an electrolytic cell or other medium.

electrolysis: Generally, a technique that uses an electric current to drive an otherwise non-spontaneous chemical reaction. Typically, an electrical potential is applied across a pair of electrodes (anode and cathode) immersed in an electrolyte solution, resulting in the movement of positively charged ions (cations) moving toward cathode and negatively charged ions (anions) toward the anode. For copper sulfide ore, electrolysis is the final stage in the process of pyrometallurgy, in which anode copper slabs are hung in a large tank full of a copper-based electrolyte solution and an electric current is applied, resulting in the plating of copper onto 99.9% pure copper cathodes.

electrolyte: A chemical compound that conducts electricity by changing into ions when melted or dissolved into a solution.

electrolytic cell: A device that contains two electrodes in contact with an electrolyte and that brings about a non-spontaneous chemical reaction when connected to an outside source of electricity.

electron: A subatomic particle that carries a negative charge.

electrowinning: Generally, the electrodeposition of a metal from an ore that has been put in solution via a process commonly referred to as leaching; a form of electrolysis. For copper oxide ore, electrowinning is the final stage in the process of hydrometallurgy, in which concentrated copper solution from the heap leaching and solvent extraction processes is used as an electrolyte; an electric current is applied through an inert anode, resulting in the plating of copper onto 99.9% pure copper cathodes.

element: A substance that cannot be separated into simpler substances by chemical means; a pure chemical substance consisting of a single type of atom distinguished by its atomic number, which is the number of protons in its atomic nucleus. Elements are divided into metals, metalloids, and nonmetals.

exploration: In mining, the process of analyzing an area of land to find mineral deposits and acquiring the rights to explore for mineral deposits on that land.

extraction: In mining, the process of removing ore from the earth in large quantities. May also be referred to as “production” or “exploitation.”

froth floatation: Generally, a process for selectively separating hydrophobic (do not mix with water) materials from hydrophilic (do mix with water) materials. For copper sulfide ore, froth floatation is the first stage in the process of pyrometallurgy, in which air bubbles are introduced into a mixture of finely crushed ore with water and a chemical that aids attachment of the bubbles to the particles of copper, which are recovered as a floating froth.

geochemistry: The science that applies chemistry to geological systems to understand the composition, structure, and processes of the earth.

geophysics: The science that applies physics to the geological systems to understand physical properties and processes of the earth and its surrounding environment.

geology: The science that deals with the dynamics and physical history of the earth, the rocks of which it is composed, and the physical, chemical, and biological changes that the earth has undergone or is undergoing.

heap leaching: Generally, an industrial mining process in which a valuable metal is extracted from a heap, or pile, of crushed ore. For copper oxide ore, heap leaching is the first stage in the process of hydrometallurgy, in which a chemical solution is applied to a heap of crushed ore, through which it percolates, dissolving the copper. The resulting pregnant leach solution is collected for further refining via solvent extraction and electrowinning.

hydrometallurgy: The process of extracting and purifying metals from ore at ordinary temperatures by leaching ore with liquid solvents. In copper processing, typically used with copper oxide ores and involves heap leaching, solvent extraction, and electrowinning.

ion: An electrically charged atom or molecule which can be formed by the gain or loss of an electron(s); whether the electrons are gained or lost is indicated by a minus or plus sign, respectively, and a number indicating how many. For example, Cu2+ has lost 2 electrons and carries a positive charge.

metallurgist: Someone who specializes in metallurgy, the branch of science and technology concerned with the properties of metals and their production and purification.

mine tailings: The ore waste of mines; large piles of finely-crushed, chemically processed material (also called gangue) left over after metals of interest (such as copper) have been extracted from the ore that contained them. May contain metals or other contaminants, and may be susceptible to erosion by wind or water.

mineral: A naturally occurring, inorganic, solid substance with a definite chemical composition and an ordered atomic arrangement.

mineral resource: A concentration or deposit of minerals in the earth’s crust which is potentially valuable.

native copper: An uncombined (pure) form of copper which occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements.

open-pit mining: A type of surface mining in which massive, usually metallic mineral deposits are removed by cutting benches in the walls of a broad, deep funnel-shaped excavation which is open to the surface for the duration of the mine's life. This form of mining differs from underground mining that requires tunneling into the earth.

ore: A naturally occurring mineral containing valuable elements (often metals) which can be extracted from the surrounding mineral at a profit.

ore reserve: A concentration or deposit of minerals in the earth’s crust which is valuable and can be mined at a profit.

oxidize: To cause an atom or group of atoms to lose electrons during a chemical reaction.

prospecting: In mining, the process of physically searching a region for mineral deposits.

pyrometallurgy: The process of extracting and purifying metals from ore using high temperatures. In copper processing, is typically used with copper sulfide ores, and involves froth flotation, thickening, smelting, and electrolysis.

reclamation: In mining, the process of restoring land that has been mined to a more natural or economically usable state.

smelting: Generally, extraction of a metal from its ore by a process that involves heating it beyond its melting point; takes place at a smelter. For copper sulfide ore, smelting is a stage in the process of pyrometallurgy, in which a series of steps use heat and a chemical reducing agent to decompose the partially processed ore, drive off other elements as gases or slag (waste), and leave just the concentrated copper base behind. The final product is a copper anode slab which is then refined in a final step called electrolysis.

solvent extraction: Generally, a process in which two immiscible (unmixing) liquids are vigorously mixed in an attempt to disperse one in the other so that solutes can migrate from one solvent to the other. For copper oxide ore, solvent extraction is a stage in the process of hydrometallurgy, in which copper-rich pregnant leach solution from the heap leaching stage is mixed vigorously with a solvent, allowing the copper to migrate into the solvent and be separated out. This solution will then act as the copper source/electrolyte for the electrowinning stage.

Superfund Alternative Site: Although it is not listed on the United States Environmental Protection Agency’s National Priorities List (NPL) with Superfund Sites, the Superfund Alternative approach uses the same investigation and cleanup process and standards that are used for sites listed on the NPL. The criteria that must be met for a site to be identified as Superfund Alternative are: site contaminants are significant enough that the site would be eligible for listing on the NPL; a long-term response (i.e., a remedial action) is anticipated at the site; and the site owner is willing to negotiate and sign an agreement with EPA to perform the investigation or cleanup.

thickening: For copper sulfide ore, a stage in the process of pyrometallurgy, in which the copper froth from the froth floatation stage is poured into large tanks called thickeners, where the copper solids settle and are filtered to remove excess water; this copper concentrate will then undergo smelting.

verdigris: A blue-green layer that forms on copper, brass, or bronze after atmospheric oxidation, or weathering.


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