What is involved in processing a mineral resource?
Except for certain nonmetallic minerals, mineral resources usually must be separated from the other materials with which they occur. The separation of minerals such as diamond, mica, and rutile is relatively simple, usually involving only simple hand or mechanical processes. The processing of metallic ores is closely related to the complexity of the ore itself and to the needed purity of the desired end product. Certain elements are deleterious to the refining process, and attempts to eliminate them early in the processing stream ensue. For example, sulfur is a poison in the processing of iron ore; some ores must be roasted to drive off the sulfur as sulfur dioxide gas; manganese is added later in the process to get rid of the small quantity remaining.
Metallic minerals are in many cases so intimately mixed with undesirable minerals that the ore must be ground to particles finer than talcum powder to permit separation, as in the case of taconite (a mixture of iron oxide and silica). Varied means of separating ore minerals from the gangue (undesirable minerals) depend upon grain size, differences in specific gravity, differences in adhesion to air bubbles between different minerals, differences in magnetic susceptibility, differences in reaction to various chemicals added to the mix, and so forth.
All of these processes depend on natural properties of the various minerals; continuing study and development result in new processes. All demand energy input, and many demand expensive complex machinery and proficient operators.
Once the desired mineral has been separated from the gangue, the desired element must be chemically separated from other components of the mineral; e.g., copper must be separated from the iron and sulfur with which it is combined in the mineral chalcopyrite and from any impurities in the mineral. The degree to which the element must be purified depends on the use to which it is to be put. More than 99.9% purity is demanded for special uses of many metals. Costs naturally rise dramatically as even greater purity is demanded.
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What are the uses of some of the more familiar mineral resources?
Mineral resources are basic to our civilization. They are essential to food, shelter, energy, industry, and defense. The jobs and enterprises that provide the United States with one of the world's highest standards of living depend on the assured availability of a wide array of mineral resources:
| Copper is used in wires for transmitting electricity. It is used in motors, telephones and telegraph, television, computers, domestic appliances, in functional and decorative hardware, and in money. |
| Iron and steel are vital to the manufacturing and construction industries. These metals are used in cars, trains, buildings, bridges, missiles, and in many household and commercial products. |
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| Lead is used in batteries, as a fuel additive, as weights, as x-ray shielding, and in noise reduction. |
| Coal is best known as a fuel and for the production of coke for steelmaking. The by-products of coke include gas heating and lighting, ammonia, coal tar, and light oils. Coal was the original basis for our petrochemical industry, which is so important in the production of synthetic materials. |
| Gold is a precious metal that has been used widely as a medium of exchange and a measure of value in world commerce. It is used in jewelry, the decorative arts, dentistry, for electrical contacts, laboratory equipment, in the field of optics, as well as in defense weapon systems. |
| Silver is used in photography, medicine, electrical appliances, automotive parts, air conditioners, refrigerator equipment, jewelry, silverware, and money. |
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| Uses of zinc include die casting, galvanizing brass and bronze, and in the production of zinc oxide for paints. |
| Salt is used in snow and ice removal, as a raw material in the manufacture of many chemicals, and as a food additive in the home and for livestock |
| These minerals are used in the manufacture of chemicals and fertilizer. |
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| Uranium is used in nuclear reactors to produce electricity, in color televisions, and in cancer therapy. Borax is used in the making of glass, photographic chemicals, and cleaning compounds. |
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