Dictionary:

copper¹

  (kŏp'ər)

1. (Symbol Cu) A ductile, malleable, reddish-brown metallic element that is an excellent conductor of heat and electricity and is widely used for electrical wiring, water piping, and corrosion-resistant parts, either pure or in alloys such as brass and bronze. Atomic number 29; atomic weight 63.54; melting point 1,083°C; boiling point 2,595°C; specific gravity 8.96; valence 1, 2.
2. A coin, usually of small denomination, made of copper or a copper alloy.
3. Chiefly British. A large cooking pot made of copper or often of iron.
4. Any of various small butterflies of the subfamily Lycaeninae, having predominantly copper-colored wings.
5. A reddish brown.

1. To coat or finish with a layer of copper.
2. Slang. To bet against, as in faro.

[Middle English coper, from Old English, from Late Latin cuprum, from Latin Cyprium (aes), Cyprian (metal), from Cyprius, of Cyprus, from Greek Kuprios, from Kupros, Cyprus.]

Background

Copper is one of the basic chemical elements. In its nearly pure state, copper is a reddish-orange metal known for its high thermal and electrical conductivity. It is commonly used to produce a wide variety of products, including electrical wire, cooking pots and pans, pipes and tubes, automobile radiators, and many others. Copper is also used as a pigment and preservative for paper, paint, textiles, and wood. It is combined with zinc to produce brass and with tin to produce bronze.

Copper was first used as early as 10,000 years ago. A copper pendant from about 8700 B.C. was found in what is now northern Iraq. There is evidence that by about 6400 B.C. copper was being melted and cast into objects in the area now known as Turkey. By 4500 B.C., this technology was being practiced in Egypt as well. Most of the copper used before 4000 B.C. came from the random discovery of isolated outcroppings of native copper or from meteorites that had impacted Earth. The first mention of the systematic extraction of copper ore comes from about 3800 B.C. when an Egyptian reference describes mining operations on the Sinai Peninsula.

In about 3000 B.C., large deposits of copper ore were found on the island of Cyprus in the Mediterranean Sea. When the Romans conquered Cyprus, they gave the metal the Latin name aes cyprium, which was often shortened to cyprium. Later this was corrupted to cuprum, from which the English word copper and the chemical symbol Cu are derived.

In South America, copper objects were being produced along the northern coast of Peru as early as 500 B.C., and the development of copper metallurgy was well advanced by the time the Inca empire fell to the conquering Spanish soldiers in the 1500s.

In the United States, the first copper mine was opened in Branby, Connecticut, in 1705, followed by one in Lancaster, Pennsylvania, in 1732. Despite this early production, most copper used in the United States was imported from Chile until 1844, when mining of large deposits of high-grade copper ore around Lake Superior began. The development of more efficient processing techniques in the late-1800s allowed the mining of lower-grade copper ores from huge open-pit mines in the western United States.

Today, the United States and Chile are the world's top two copper producing countries, followed by Russia, Canada, and China.

Raw Materials

Pure copper is rarely found in nature, but is usually combined with other chemicals in the form of copper ores. There are about 15 copper ores mined commercially in 40 countries around the world. The most common are known as sulfide ores in which the copper is chemically bonded with sulfur. Others are known as oxide ores, carbonate ores, or mixed ores depending on the chemicals present. Many copper ores also contain significant quantities of gold, silver, nickel, and other valuable metals, as well as large quantities of commercially useless material. Most of the copper ores mined in the United States contain only about 1.2-1.6% copper by weight.

The most common sulfide ore is chalcopyrite, CuFeS₂, also known as copper pyrite or yellow copper ore. Chalcocite, Cu₂S, is another sulfide ore.

Cuprite, or red copper ore, Cu₂O, is an oxide ore. Malachite, or green copper ore, Cu(OH)₂•CuCO₃, is an important carbonate ore, as is azurite, or blue copper carbonate, Cu(OH)₂•2CuCO₃.

Other ores include tennantite, boronite, chrysocolla, and atacamite.

In addition to the ores themselves, several other chemicals are often used to process and refine copper. These include sulfuric acid, oxygen, iron, silica, and various organic compounds, depending on the process used.

The Manufacturing
Process

The process of extracting copper from copper ore varies according to the type of ore and the desired purity of the final product. Each process consists of several steps in which unwanted materials are physically or chemically removed, and the concentration of copper is progressively increased. Some of these steps are conducted at the mine site itself, while others may be conducted at separate facilities.

Here are the steps used to process the sulfide ores commonly found in the western United States.

Mining

• Most sulfide ores are taken from huge open-pit mines by drilling and blasting with explosives. In this type of mining, the material located above the ore, called the overburden, is first removed to expose the buried ore deposit. This produces an open pit that may grow to be a mile or more across. A road to allow access for equipment spirals down the interior slopes of the pit.
• The exposed ore is scooped up by large power shovels capable of loading 500-900 cubic feet (15-25 cubic meters) in a single bite. The ore is loaded into giant dump trucks, called haul trucks, and is transported up and out of the pit.

Concentrating

The copper ore usually contains a large amount of dirt, clay, and a variety of non-copper bearing minerals. The first step is to remove some of this waste material. This process is called concentrating and is usually done by the flotation method.

• The ore is crushed in a series of cone crushers. A cone crusher consists of an interior grinding cone that rotates on an eccentric vertical axis inside a fixed outer cone. As the ore is fed into the top of the crusher, it is squeezed between the two cones and broken into smaller pieces.
• The crushed ore is then ground even smaller by a series of mills. First, it is mixed with water and placed in a rod mill, which consists of a large cylindrical container filled with numerous short lengths of steel rod. As the cylinder rotates on its horizontal axis, the steel rods tumble and break up the ore into pieces about 0.13 in (3 mm) in diameter. The mixture of ore and water is further broken up in two ball mills, which are like a rod mill except steel balls are used instead of rods. The slurry of finely ground ore that emerges from the final ball mill contains particles about 0.01 in (0.25 mm) in diameter.
• The slurry is mixed with various chemical reagents, which coat the copper particles. A liquid, called a frother, is also added. Pine oil or long-chain alcohol are often used as frothers. This mixture is pumped into rectangular tanks, called flotation cells, where air is injected into the slurry through the bottom of the tanks. The chemical reagents make the copper particles cling to the bubbles as they rise to the surface. The frother forms a thick layer of bubbles, which overflows the tanks and is collected in troughs. The bubbles are allowed to condense and the water is drained off. The resulting mixture, called a copper concentrate, contains about 25-35% copper along with various sulfides of copper and iron, plus smaller concentrations of gold, silver, and other materials. The remaining materials in the tank are called the gangue or tailings. They are pumped into settling ponds and allowed to dry.

Smelting

Once the waste materials have been physically removed from the ore, the remaining copper concentrate must undergo several chemical reactions to remove the iron and sulfur. This process is called smelting and traditionally involves two furnaces as described below. Some modern plants utilize a single furnace, which combines both operations.

• The copper concentrate is fed into a furnace along with a silica material, called a flux. Most copper smelters utilize oxygen-enriched flash furnaces in which preheated, oxygen-enriched air is forced into the furnace to combust with fuel oil. The copper concentrate and flux melt, and collect in the bottom of the furnace. Much of the iron in the concentrate chemically combines with the flux to form a slag, which is skimmed off the surface of the molten material. Much of the sulfur in the concentrate combines with the oxygen to form sulfur dioxide, which is exhausted from the furnace as a gas and is further treated in an acid plant to produce sulfuric acid. The remaining molten material in the bottom of the furnace is called the matte. It is a mixture of copper sulfides and iron sulfides and contains about 60% copper by weight.
• The molten matte is drawn from the furnace and poured into a second furnace called a converter. Additional silica flux is added and oxygen is blown through the molten material. The chemical reactions in the converter are similar to those in the flash furnace. The silica flux reacts with the remaining iron to form a slag, and the oxygen reacts with the remaining sulfur to form sulfur dioxide. The slag may be fed back into the flash furnace to act as a flux, and the sulfur dioxide is processed through the acid plant. After the slag is removed, a final injection of oxygen removes all but a trace of sulfur. The resulting molten material is called the blister and contains about 99% copper by weight.

Refining

Even though copper blister is 99% pure copper, it still contains high enough levels of sulfur, oxygen, and other impurities to hamper further refining. To remove or adjust the levels of these materials, the blister copper is first fire refined before it is sent to the final electrorefining process.

• The blister copper is heated in a refining furnace, which is similar to a converter described above. Air is blown into the molten blister to oxidize some impurities. A sodium carbonate flux may be added to remove traces of arsenic and antimony. A sample of the molten material is drawn and an experienced operator determines when the impurities have reached an acceptable level. The molten copper, which is about 99.5% pure, is then poured into molds to form large electrical anodes, which act as the positive terminals for the electrorefining process.
• Each copper anode is placed in an individual tank, or cell, made of polymer-concrete. There may be as many as 1,250 tanks in operation at one time. A sheet of copper is placed on the opposite end of the tank to act as the cathode, or negative terminal. The tanks are filled with an acidic copper sulfate solution, which acts as an electrical conductor between the anode and cathode. When an electrical current is passed through each tank, the copper is stripped off the anode and is deposited on the cathode. Most of the remaining impurities fall out of the copper sulfate solution and form a slime at the bottom of the tank. After about 9-15 days, the current is turned off and the cathodes are removed. The cathodes now weigh about 300 lb (136 kg) and are 99.95-99.99% pure copper.
• The slime that collects at the bottom of the tank contains gold, silver, selenium, and tellurium. It is collected and processed to recover these precious metals.

Casting

• After refining, the copper cathodes are melted and cast into ingots, cakes, billets, or rods depending on the final application. Ingots are rectangular or trapezoidal bricks, which are remelted along with other metals to make brass and bronze products. Cakes are rectangular slabs about 8 in (20 cm) thick and up to 28 ft (8.5 m) long. They are rolled to make copper plate, strip, sheet, and foil products. Billets are cylindrical logs about 8 in (20 cm) in diameter and several feet (meters) long. They are extruded or drawn to make copper tubing and pipe. Rods have a round cross-section about 0.5 in (1.3 cm) in diameter. They are usually cast into very long lengths, which are coiled. This coiled material is then drawn down further to make copper wire.

Quality Control

Because electrical applications require a very low level of impurities, copper is one of the few common metals that are refined to almost 100% purity. The process described above has been proven to produce copper of very high purity. To ensure this purity, samples are analyzed at various steps to determine whether any adjustment to the process is required.

Byproducts/Waste

The recovery of sulfuric acid from the copper smelting process not only provides a profitable byproduct, but also significantly reduces the air pollution caused by the furnace exhaust. Gold, silver, and other precious metals are also important byproducts.

Waste products include the overburden from the mining operation, the tailings from the concentrating operation, and the slag from the smelting operation. This waste may contain significant concentrations of arsenic, lead, and other chemicals, which pose a potential health hazard to the surrounding area. In the United States, the Environmental Protection Agency (EPA) regulates the storage of such wastes and the remediation of the area once mining and processing operations have ceased. The sheer volume of the material involved—in some cases, billions of tons of waste—makes this a formidable task, but it also presents some potentially profitable opportunities to recover the useable materials contained in this waste.

The Future

Demand for copper is expected to remain high, especially in the electrical and electronics industries. The current trends in copper processing are towards methods and equipment that use less energy and produce less air pollution and solid waste. In the United States, this is a difficult assignment because of the stringent environmental controls and the very low-concentration copper ores that are available. In some cases, the production costs may increase significantly.

One encouraging trend is the increased use of recycled copper. Currently over half the copper being produced in the United States comes from recycled copper. Fifty-five percent of the recycled copper comes from copper machining operations, such as screw forming, and 45% comes from the recovery of used copper products, such as electrical wire and automobile radiators. The percentage of recycled copper is expected to grow as the costs of new copper processing increase.

Where to Learn More

Books

Brady, George S., Henry R. Clauser, and John A. Vaccari. Materials Handbook. McGraw-Hill, 1997.

Heiserman, David L. Exploring Chemical Elements and Their Compounds. TAB Books, 1992.

Hombostel, Caleb. Construction Materials. John Wiley and Sons, Inc., 1991.

Kroschwitz, Jacqueline I. and Mary Howe-Grant, ed. Encyclopedia of Chemical Technology. John Wiley and Sons, Inc., 1993.

Stwertka, Albert. A Guide to the Elements. Oxford University Press, 1996.

Periodicals

Baum, Dan and Margaret L. Knox. "We want people who have a problem with mine wastes to think of Butte." Smithsonian (November 1992): 46-52, 54-57.

Shimada, Izumi and John F. Merkel. "Copper-Alloy Metallurgy in Ancient Peru." Scientific American (July 1991): 80-86.

Other

http://www.copper.org.

http://www.intercorr.com/periodic/29.htm.

http://innovations.copper.org/innovations.html.

[Article by: Chris Cavette]

A chemical element, Cu, atomic number 29, atomic weight 63.546. Copper, a nonferrous metal, is the twentieth most abundant element present in the Earth's crust, at an average level of 68 parts per million (0.22 lb/ton or 0.11 kg/metric ton). Copper metal and copper alloys have considerable technological importance due to their combined electrical, mechanical, and physical properties. The discoveries that mixed-valence Cu(II)/Cu(III) oxides exhibit superconductivity (zero electrical resistance) at temperatures as high as 125 K (−234°F; liquid nitrogen, a cheap coolant, boils at 90 K or −297°F) have generated intense international competition to understand these new materials and to develop technological applications. Although some pure copper metal is present in nature, commercial copper is obtained by reduction of the copper compounds in ores followed by electrolytic refining. The rich chemistry of copper is restricted mostly to the valence states Cu(I) and Cu(II); compounds containing Cu(0), Cu(III), and Cu(IV) are uncommon. Soluble copper salts are potent bacteriocides and algicides at low levels and toxic to humans in large doses. Yet copper is an essential trace element that is present in various metalloproteins required for the survival of plants and animals.

Copper is located in the periodic table between nickel and zinc in the first row of transition elements and in the same subgroup as the other so-called coinage metals, silver and gold. The electronic configuration of elemental copper is [1s²2s²2p⁶3s²] 3d¹⁰4s¹ or [argon]3d¹⁰4s¹. At first glance, the sole 4s electron might suggest chemical similarity to potassium, which has the [argon]4s¹ configuration. However, metallic copper, in sharp contrast to metallic potassium, is relatively unreactive. The higher nuclear charge of copper relative to that of potassium is not fully shielded by the 10 additional d electrons, with the result that the copper 4s electron has a higher ionization potential than that of potassium (745.5 versus 418.9 kilojoules/mole, respectively). Moreover, the second and third ionization potentials of copper (1958.1 and 3554 J/mole, respectively) are considerably lower than those of potassium, and account for the higher valence-state accessibility associated with transition-metal chemistry as opposed to alkali-metal chemistry. See also Electron configuration; Periodic table; Transition elements; Valence.

Copper is a comparatively heavy metal. The density of the pure solid is 8.96 g/cm³ (5.18 oz/in.³) at 20°C (68°F). The density of commercial copper varies with method of manufacture, averaging 8.90–8.92 g/cm³ (5.14–5.16 oz/in.³) in cast refinery shapes, 8.93 g/cm³ (5.16 oz/in.³) for annealed tough-pitch copper, and 8.94 g/cm³ (517 oz/in.³) for oxygen-free copper. The density of liquid copper is 8.22 g/cm³ (4.75 oz/in.³) near the freezing point.

The melting point of copper is 1083.0 ∓ 0.1°C (1981.4 ∓ 0.2°F). Its normal boiling point is 2595°C (4703°F).

The coefficient of linear expansion of copper is 1.65 × 10⁻⁵/°C at 20°C.

The specific heat of the solid is 0.092 cal/g at 20°C (68°F). The specific heat of liquid copper is 0.112 cal/g, and of copper in the vapor state about 0.08 cal/g.

The electrical resistivity of copper in the usual volumetric unit, that of a cube measuring 1 cm in each direction, is 1.6730 × 10⁻⁶ ohm · cm at 20°C (68°F). Only silver has a greater volumetric conductivity than copper. On a relative basis in which silver is rated 100, copper is 94, aluminum 57, and iron 16.

The mass resistivity of pure copper for a length of 1 m weighing 1 g at 20°C (68°F) is 0.14983 ohm. The conductivity of copper on the mass basis is surpassed by several light metals, notably aluminum. The relative values are 100 for aluminum, 50 for copper, and 44 for silver.

By far the largest use of copper is in the electrical industry, and therefore high electrical conductivity is its most important single property, although for industrial use this property must be accompanied by suitable characteristics in other respects. See also Conductor (electricity).

Copper-containing proteins provide diverse biochemical functions, including copper uptake and transport (ceruloplasmin), copper storage (metallothionen), protective roles (superoxide dismutase), catalysis of substrate oxygenation (dopamine β-monooxygenase), biosynthesis of connective tissue (lysyl oxidase), terminal oxidases for oxygen metabolism (cytochrome c oxidase), oxygen transport (hemocyanin), and electron transfer in photosynthetic pathways (plastocyanin). See also Enzyme.

A dietary essential trace metal, which forms the prosthetic group of a number of enzymes. The Reference Nutrient Intake is 1.2 mg/day. Toxic in excess, and it is recommended that not more than 2-10 mg/day should be consumed habitually. Rich sources include: meat, poultry, game, fish and shellfish, avocado, nuts, pulses, bread, chocolate, beer, cider, coconut, mushrooms.

An essential element involved in many processes including red blood cell formation, respiration, and bone formation. Copper deficiencies are rare, mainly because most domestic water supplies are contaminated with copper from pipes, but low intakes can lead to anaemia. Oysters and liver are good sources of dietary copper. In the UK, the adult Reference Nutrient Intake for copper is 1.2 mg each day. In the USA, the estimated safe and adequate daily intake of copper is 1.5-3.0 mg. Blood levels of copper often decrease after exercise indicating that athletes may need higher than normal intakes. Copper and zinc appear to be antagonistic; high intakes of one tend to reduce the absorption of the other. Copper toxicity is rare, but intakes greater than 20 mg cause vomiting and nausea.

Conventional electron-carrying network cable with a core conductor of copper — or aluminum! Opposed to light pipe or, say, a short-range microwave link.

Description

Copper is an essential mineral that plays an important role in iron absorption and transport. It is considered a trace mineral because it is needed in very small amounts. Only 70–80 mg of copper are found in the body of a normal healthy person. Even though the body needs very little, copper is an important nutrient that holds many vital functions in the body.

Copper is essential for normal development of the body because it:

• Participates in a wide variety of important enzymatic reactions in the body.
• Is a component of or a cofactor for approximately 50 different enzymes. These enzymes need copper to function properly.
• Is essential for iron absorption and transport. Iron is needed to make hemoglobin, a main component of red blood cells. Therefore, copper deficiency is often linked to iron-deficiency anemia.
• Is required to build elastin and collagen, which are an important components of bones and connective tissues. Therefore, copper is believed to protect the bones and joints against degeneration and osteoporosis.
• Is required for melanin production. People with copper deficiency may have pale skin and hair.
• Is a key mineral for the immune system. Copper promotes wound healing. Studies show that premature infants or children with genetic copper defects are at high risk of getting infections and would significantly improve with copper supplementation.
• Attacks free radicals. Copper is a strong antioxidant. It works by attaching itself to the enzyme Superoxide dismutase (SOD). Copper also binds to a protein to form ceruloplasmin, which is an antioxidant.
• Helps the body produce energy. Copper participates in many oxidative reactions that break down fats in fat tissue to produce much needed energy. Copper deficiency has been associated with high cholesterol levels.
• Is necessary for normal functioning of insulin. Copper deficiency is also associated with poor blood glucose control.
• Is needed for normal functioning of the cardiovascular system.
• Protects the structure and function of the nervous system, including the brain. Copper protects nerve fiber by maintaining myelin, the insulating sheath that surrounds nerve cells. It also aids the transmission of nerve signals in the brains.

General Use

Copper supplements may be beneficial in treating or preventing copper deficiency. Copper deficiency used to be relatively rare because the body requires so little of it, only about 2 mg per day. In addition, it is available naturally in a variety of foods such as whole grains, shellfish, nuts, beans, and leafy vegetables. Additional sources of copper are the copper water pipes that run through homes or the copper cookware in the kitchen. These sources leach copper into the water we drink and the food we eat. The level of copper in drinking water is sometimes so high that it becomes a public concern. However, scientists now realize that copper deficiency, especially borderline cases, is more common than once thought. Copper deficiency is currently on the rise due to a decrease of whole foods in the diet and high consumption of fatty and processed foods.

It was discovered in 2001 that vegetarian diets generally contain more copper, but that the absorption efficiency was lower for lactoovo vegetarians than for nonvegetarians. The study also showed that the increased amounts of copper in the vegetarian diets allow for greater copper content.

Besides dietary causes, certain diseases or conditions may reduce copper absorption, transport or increase its requirements, resulting in abnormally low copper blood levels. Increased copper intake through diet or supplementation may be necessary in the following conditions:

• premature infants fed only cow's milk
• pregnant women
• malnutrition
• celiac disease, sprue, cystic fibrosis, or short-bowel syndrome (these diseases cause poor absorption of dietary copper)

• kidney disease
• high consumption of zinc or iron (these minerals interfere with copper absorption)
• highly processed foods (copper is stripped away during food processing)
• Menkes syndrome (copper deficiency is caused by genetic defects of copper transport; Menkes syndrome patients cannot use copper supplied by the diet efficiently)

Symptoms of copper deficiency include:

• anemia
• malnourished infants
• prominently dilated veins
• pale hair or skin
• poorly formed bones
• nervous system disorders
• high cholesterol levels
• heart disease
• loss of taste
• increased susceptibility to infections
• infertility
• birth defects

Exceeding the daily requirement is dangerous, however, because copper toxicity commonly occurs. Copper toxicity is a very serious medical problem. Acute toxicity due to ingestion of too much supplement, for example, may cause nausea, vomiting, abdominal pain, diarrhea, dizziness, headache, and a metallic taste in the mouth. Chronic toxicity is often caused by genetic defects of copper metabolism, such as Wilson's disease. In this disease, copper is not eliminated properly and is allowed to accumulate to toxic levels. Copper is therefore present at high concentration where it should not be, such as in the liver, the lens of the eye, kidneys, or brain.

Disease Prevention

Copper is a good antioxidant. It works together with an antioxidant enzyme, superoxide dismutase (SOD), to protect cell membranes from being destroyed by free radicals. Free radicals are any molecules that are missing one electron. Because this is an unbalanced and unstable state, a radical is desperately finding ways to complete its pair. Therefore, it reacts to any nearby molecules to either steal an electron or give away the unpaired one. In the process, free radicals initiate chain reactions that destroy cell structures. Like other antioxidants, copper scavenges or cleans up these highly reactive radicals and changes them into inactive, less harmful compounds. Therefore, it can help prevent cancer. In 2001, a study reported that concentrations of copper sulfate and ascorbate may inhibit breast cancer growth. With further study, the combination may even prove useful as a chemotherapy agent for certain breast cancer patients.

Copper may also help prevent degenerative diseases or conditions such as premature aging, heart disease, autoimmune diseases, arthritis, cataracts, Alzheimer's disease, or diabetes.

Osteoporosis

Copper may play a role in preventing osteoporosis. Calcium and vitamin D have long been considered the mainstay of osteoporosis treatment and prevention. However, a recent study has shown that they can be even more effective in increasing bone density and preventing osteoporosis if they are used in combination with copper and two other trace minerals, zinc and manganese.

Rheumatoid Arthritis

Copper has been a folklore remedy for rheumatoid arthritis since 1500 B.C. in ancient Egypt. Some people believe that wearing jewelry made of copper may relieve arthritic symptoms. To evaluate the effect of copper for the treatment of rheumatoid arthritis, Dr. Walker and his colleagues conducted a study of 77 arthritic patients. Patients were divided into two groups: treatment group wearing copper jewelry and placebo group wearing nothing or aluminum jewelry. In this study, patients who wore copper bracelets felt significantly better than those in the placebo group. In addition, patients in the treatment group reported recurrences of symptoms after the bracelets were removed. To explain the effects of the copper bracelets, these researchers suggested that copper contained in the bracelets was dissolved in sweat and then absorbed through the skin. They suspected that copper's effectiveness may be related to its role as an antioxidant. They also believe that copper may function as both an anti-inflammatory agent and as an antioxidant. Thus, it is possibly effective in reducing inflammatory response to such conditions as rheumatoid arthritis.

Preparations

Copper is contained in many multivitamin/mineral preparations. It is also available as a single ingredient in the form of tablets. These tablets should be swallowed whole with a cup of water, preferably with meals, to avoid stomach upset. A person may choose any of the following preparations: copper gluconate, copper sulfate, or copper citrate. However, copper gluconate may be the least irritating to the stomach.

Zinc and copper compete with each other for absorption in the gastrointestinal tract. As a result, excessive copper intake may cause zinc deficiency, and vice versa. Therefore, a person should take zinc and copper supplements together in ratios of 10:1 or 15:1.

Precautions

Those adding copper supplements to their diets should consider:

• Informing their doctors for proper instruction and monitoring of side effects. Copper toxicity due to excessive doses of copper supplements has been reported.
• Although there currently is no recommended daily allowance (RDA) established for copper, 2 mg of copper per day is considered sufficient and safe. Nausea and vomiting may occur in persons taking more than 20 mg of copper daily.
• It is not known if copper supplementation may harm a growing fetus. However, as with any drugs, pregnant or nursing women should not take copper or any other supplements or drugs without first consulting their doctors.
• In certain areas, drinking water may contain high levels of copper. Periodic checks of copper levels in drinking water may be necessary.
• Because individual antioxidants often work together as a team to defend the body against free radicals, the balance between copper, zinc, and iron must be maintained. Excessive intake of one nutrient might result in a deficiency of other minerals and decreased resistance to infections and increased risk of heart disease, diabetes, arthritis, and other diseases.

Side Effects

A person should stop taking copper supplements and seek medical help immediately if having the following signs or symptoms:

• anemia
• nausea
• vomiting
• abdominal pain

Interactions

Factors That Increase Copper Concentrations

Certain disorders have been known to increase copper levels. Persons with these conditions should not take copper supplements as they may cause copper toxicity.

• recent heart attacks
• lupus erythematosus
• cirrhosis of the liver
• schizophrenia
• leukemia and some other forms of cancer
• viral infections
• ulcerative colitis (This inflammatory bowel disease may cause accumulation of copper in the body. Excessive amount of copper may worsen many symptoms of this disease by increasing susceptibility to infections and inhibiting wound healing.)
• Wilson's disease (This disease causes accumulation of copper in the tissues. As a result, patients have liver disease, mental retardation, tremor and poor muscle coordination. They also have copper deposits in the cornea of the eye. To manage this disease, patients are put on a low-copper diet and given penicillamine, a drug that attaches itself to copper and increases its excretion.)

Resources

Books

Lieberman,, Shari and Nancy Bruning. "Copper." In The Real Vitamin & Mineral Book: Using Supplements for Optimum Health Garden City Park, NY: Avery Publishing Group, 1997.

Passwater, Richard A. All About Antioxidants. Garden City Park, NY: Avery Publishing Group, 1998.

Periodicals

Gonzalez, M. J, et al. "Inhibition of Human Breast Carcinoma Cell Proliferation by Ascorbate and Copper."The Journal of Nutrition 131, no. 11 (November 2001): 3142S.

Hunt, Janet R., and Richard A. Vanderpool. "Apparent Copper Absorption from a Vegetarian Diet."American Journal of Clinical Nutrition 74, no. 6 (December 2001): 803–805.

Reginster, Jean-Yves, Anne Noel Taquet, and Christiane Gosset. "Therapy for Osteoporosis: Miscellaneous and Experimental Agents."Endocrinology and Metabolism Clinics (June 1998): 453–463.

Uauy, Ricardo, Manuel Olivarez, and Mauricio Gonzales. "Essentiality of Copper in Humans."American Journal of Clinical Nutrition 67 suppl (1998): 952S–959S.

Other

"Copper" The Merck Manual of Diagnosis and Therapy. [cited October 2002]. . Rosenstein, Elliot D., and Jacques R. Caldwell. "Therapies: Trace Elements in the Treatment of Rheumatic Conditions." In Rheumatic Diseases Clinics of North America. Part II. [cited May 2000]. .

[Article by: Mai Tran; Teresa G. Odle]

(click to enlarge)
Crystalline copper from Michigan (credit: Courtesy of Ted Boente Collection; photograph, John H. Gerard)

Metallic chemical element, one of the transition elements, chemical symbol Cu, atomic number 29. Sometimes found in the free state in nature, it is a reddish metal, very ductile and an unusually good conductor of electricity and heat. Most of the world's copper production is used by the electrical industries; the remainder is combined with other metals (e.g., zinc, tin, nickel) to form alloys such as brass, bronze, nickel silver, and Monel. Copper is part of nearly all coinage metals. In compounds copper usually has valence 1 (cuprous) or 2 (cupric). Cuprous compounds include cuprous oxide, a red pigment and a fungicide; cuprous chloride, a catalyst for certain organic reactions; and cuprous sulfide, with a variety of uses. Cupric compounds include cupric oxide, a pigment, decolorizing agent, and catalyst; cupric chloride, a catalyst, wood preservative, mordant, disinfectant, feed additive, and pigment; and cupric sulfate, a pesticide, germicide, feed additive, and soil additive. Copper is a necessary trace element in the human diet and essential to plant growth; in blue-blooded mollusks and crustaceans it plays the same role in hemocyanin as iron does in hemoglobin.

For more information on copper, visit Britannica.com.

A lustrous reddish metal, highly ductile and malleable; has high tensile strength, is an excellent electrical and thermal conductor, is available in a wide variety of shapes; widely used for downspouts, electrical conductors, flashing, gutters, roofing, etc.

An essential element involved in many processes including red blood cell formation, blood-sugar regulation, and bone formation. Deficiency may cause anaemia and feelings of lassitude.

Environment

In the upper levels of copper sulfide veins and in some types of volcanic rock.

Usually in distorted, often rounded, complex crystals, with cubes, dodecahedrons, and octahedrons predominant. Often in hackly masses (Michigan) and in sheets without recognizable crystal forms.

Copper color. Luster metallic; hardness 2Ɖ-3; specific gravity 8.9. Malleable and ductile.

Fairly pure as a rule, often alloyed with small amounts of silver, arsenic, iron, etc.

Small bits fuse on charcoal to black-coated copper button; malleable, soluble in acids, giving greenish solutions. Colors flame blue-green.

Almost inescapable green and blue stains on rock outcrops, known as "copper blooms," are a guide to deposits of copper and its associated minerals. The malleability and the color are distinguishing characteristics.

Since weathering processes free copper from its primary ore, chalcopyrite (CuFeS ₂ ), it is likely to be found in the cap rock (the gossan) of copper-bearing sulfide veins, particularly in arid climates. Native copper is also found in ancient lava flows, where iron and oxygen have robbed the magma of sulfur. It is abundant in this form in Michigan's Upper Peninsula, where copper has been deposited in a thick series of flows, and this is the only economic source where all the copper is in the native state. Great masses found in these deposits were hard to remove because of their size and the difficulty of breaking them up. Nuggets from this deposit carried south by the glacier were scattered across the north-central states and were manufactured by the Indians into copper artifacts. Native copper was once found in Chessy, France, and Cornwall, England. Today it is abundant in some of the Arizona mines still working in the upper levels, like Morenci and Ajo. Surprisingly, it is not a major mineral in Chile, though that country contains rich sources of the metal.