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www.mineralgallery.co.za Minerals A-E |
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Copper |
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Name
Copper
Chemistry
Cu
Uses
The electrical industry is a major consumer of copper. The metal is used for the windings of generators and for conveying electrical power. Its resistance to chemical attack and its high thermal conductivity make copper a useful metal for condensers in chemical plants and for car radiators. Copper tubing is widely employed in plumbing, and finely divided copper is used as an industrial catalyst in the oxidation of methanol to formaldehyde. Copper compounds, such as Fehling solution, are used in analytical tests for sugars.
Copper sulfate has many industrial applications, including the preparation of Bordeaux mixture (a fungicide), electroplating solutions, textile dyeing, and as a timber preservative. Probably its earliest use as a fungicide was in the form of copper sulfate solution employed as a seed dressing to destroy cereal disease, such as bunt.
Color
Copper color - tarnishes green
Hardness
2.5-3
Specific gravity
8.5-9 Very heavy for a metal
Crystals
Isometric, usually massive but also forms cubical and dendritic crystals
Accompanied by:
Mimetite and calcite, bornite, chalcocite
Fracture
Tectile, this means that it can bend without breaking.
Luster
Metallic
Cleavage
None
Streak
Red-Brown metallic
Similar to:
Silver
Copper was the first metal used by humans and is second only to iron in its utility through the ages. The name is derived from the Latin cuprum, "copper," from the earlier Latin Cyprium, "Cyprian metal." The discovery of the metal dates from prehistoric times, and it is estimated that copper was first used about 5000 BC or even earlier.
In Roman times copper was obtained mainly from the island of Cyprus, as the name implies. Today it is mined in many parts of the world, the largest producers at present being Chile, Peru, Poland, the United States, Congo (Zaire), and Zambia. More than 160 minerals containing copper are known. Copper constitutes 70 parts per million of the Earth's crust and is present to the extent of 0.020-0.001 parts per million in seawater.About 80% of all copper mined today, however, is derived from low-grade ores containing 2% or less of the element.
Half of the world's copper deposits are in the form of chalcopyrite ore. All important copper-bearing ores fall into two main classes: oxidized ores and sulfide ores. Sulfide ores are more important commercially. Ores are removed either by open-pit or by underground mining. Ores containing as little as 0.4% copper can be mined profitably in open-pit mining, but underground mining is profitable only if an ore contains 0.7-0.6% copper.
Deoxidized ores, such as cuprite and tenorite, can be reduced directly to metallic copper by heating with carbon in a furnace, but the sulfide ores, such as chalcopyrite and chalcocite, require a more complex treatment in which low-grade ores have to be enriched before smelting begins. This involves the ore-flotation process, in which the ore is crushed and powdered before it is agitated with water containing a foaming agent and an agent to make the copper-bearing particles water-repellent. These particles accumulate in the froth on the surface of the flotation tank, and this froth is skimmed off and heated to about 800¡ C to remove some of the water as well as antimony, arsenic, and sulfur, which are also present. The residue is then mixed with silica and melted in a furnace at 1,400-1,500¡ C. This produces two liquid layers: a lower layer of copper matte (cuprous sulfide mixed with iron sulfide and oxides), and an upper layer of silicate slag, which is drawn off. Silica or siliceous copper ore is added to the liquid matte in a converter, and air under pressure is blown through the liquid. The final stage of purification is mainly by electrolytic refining, which yields copper of 99.95-0.99.97% purity.
The luster on the surface of copper is metallic and is oftentimes green due to the copper rusting. (Oxidizing)
Copper forms in the following way, massive, wires and arborescent or branching forms as the most common, whole individual crystals are extremely rare but when present are usually cubes and octahedrons. Occasionally, massive forms will show some recognizable crystal faces on outer surfaces. Cleavage is absent. Fracture is jagged. Streak is reddish copper color. Copper is ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices. Native copper (copper found in a chemically uncombined state) has been mined for centuries and now is all but depleted as an economically viable ore. Other copper minerals are far more economical to mine and purify into metallic copper that is used for wiring, electrical components, pennies and other coins, tubing and many other applications. Native copper is still found in limited quantities in once-active mining regions. These finds are now valuable as mineralogical specimens and ornamental pieces. Fine specimens only rarely demonstrate crystal faces and these are prized above otherwise similar specimens. See our monster specimen from Tsumeb.
The normal diet of humans includes between 2 and 5 mg of copper per day, exceeding the body maintenance requirements of about 2 mg per day. The hereditary deficiency of the protein ceruloplasmin, known as Wilson disease, is associated with a pathological increase in the copper content of almost all tissues, particularly the brain and liver. Albino mammals lack the normal form of the copper-containing enzyme tyrosinase, which participates in the synthesis of the pigment melanin. Copper can be toxic in large quantities, especially to lower organisms such as bacilli, fungi, and algae.
