COPPER, MINING, PROCESSING AND THE COPPER AND BRONZE AGES

COPPER

Copper is a relatively soft, easily-tarnished, reddish metal valued in the past as component of alloys such as bronze and bronze and is prized today as an electrical conductor. The only metal that conducts electricity better is silver but it is more expensive. It is widely use in the automobile, electronics and semiconductor industries.

Copper is found in may forms: in soils, ores, mineral waters and plant and animal materials. It is often found near the earth’s surface and is easily extracted in open-pit mines. It is also taken from underground mines.

Most copper is mined in massive open-pit mines using massive shovels that scoop up ore and place it in massive 270-ton trucks that move the ore to the processing plants. In the old days trains were used to move ore. Trucks are more efficient. One mine that switched to trucks employed 3,400 workers to produce 282 million pounds of copper in 1981 with trains while using only 2,050 workers to produce 842 million pounds with monster trucks in 2003.

About 360 kilograms of ore, rock, soil and sand needs to be excavated to produce one kilogram of copper. [Source: Japanese Environmental Ministry]

World Copper Mine Production, By Country (Metric tons, 2006): 1) Chile 3,669,000; 2) Peru 875,026; 3) China 873,000; 4) Indonesia 816,000; 5) Australia 806,400; 6) Russian Federation 725,000); 7) Canada 606,958; 8) United States 594,000; 9) Poland 512,000; 10) Kazakhstan 457,000; 11) Zambia 350,000; 12) Mexico 250,000; 13) Iran, Islamic Republic Of 208,000; 14) Papua New Guinea 194,355; 15) Argentina 180,100; 16) Brazil 143,000; 17) Mongolia 129,693; 18) Uzbekistan 115,000; 19) South Africa 97,000; 20) Sweden 97,000; 21) Bulgaria 84,000; 22) Congo, The Democratic Republic Of The 81,000; 23) Portugal 78600; 24) Lao People's Democratic Republic 60803; 25) Turkey 46000 [Source: United States Geological Survey (USGS) Minerals Resources Program]

Mineral and Energy Production : United States Geological Survey (USGS) Minerals Resources Program minerals.usgs.gov/minerals/pubs/commodity ; Index Mundi indexmundi.com/minerals/ ; Energy Information Administration, Department of Energy eia.doe.gov/emeu/international ; Nationmaster nationmaster.com

Websites and Resources on Mining: Mining.com mining.com ; Wikipedia article Wikipedia ; Mining Engineering books.google.com/books ; Geology and Hard Rock Mining rmmlf.org/scitech/ ; Mining technology mining-technology.com ;

Websites and Resources on Minerals: Mineralogy Database webmineral.com ; Minerals and Gemstone Kingdom minerals.net ; Mindat.org mindat.org ; Minerals Atlas mineralatlas.com ;

Copper Processing

Copper is separated from ore either by wet or dy processing. In the dry process the ore is crushed, and some impurities are dissolved in water and removed, Using a flotation process grains of copper-bearing ore are mixed with oil and the mixture is pumped with steam. Oil clings to the metal-bearing grains and is lifted by water while the impurities sink.

The copper is then ready to be smelted. Sulphur is burned out and removed in a roasting furnace, and in the process provides much of the heat necessary to fuel the procedure. Next the impure copper is melted down in a reverberating furnace whose high temperatures are maintained by blowing air and coal. The melted product flows out as slag (waste) and matter (copper with a few impurities). The matter is refined further in a converter that uses blasts of air to burn out the remaining impurities.

In the wet process copper is dissolved from the ores by acids and converted into a water-soluble salt by roasting with a reagent. The solvent is usually sulfuric acid, hydrochloric acid or ammonia. The copper-bearing solution is run into tanks where it the copper is precipitated by metallic iron or electrolysis methods. The precipitate is refined or smelted in a converter

The "blister copper" produced in the converter is often refined again before being cast into ingots. Copper that is put through a final electrolysis process is 99.98 percent pure. Copper may be caste into square cakes for rolling purposes, round bullets made into wire or ingots that can be meted and reacts. Wire is made by a complex machine that winds a number of wires around a central core.

Traditionally the ore has been separated in a concentrator. These days many processors use the “leeching” process that has eliminate the need for a concentrator or for hot furnaces.

Copper Products

Copper is utilized for all kinds of electrical wiring, household plumbing, motors, computer parts and other uses. Copper wire was traditionally used to carry electrical power and telephone signals. These pays it being replaced in the telecommunication industry by fiber optics that can carry much more information.

The main uses for copper in the U.S. are in building and construction (41 percent), electrical and electronic products (24 percent), industrial machinery and products (13 percent), transportation (12 percent) and consumer and general goods.

Copper is easily worked. For cooking utensils it is coated with tin to prevent build up of harmful compounds. It can be rolled to 1/1000th of an inch and drawn to 5,000 times it lengths, which makes it ideal for wire. When exposed to wind and rain, it turns green and over the centuries has been used as a roofing material on many famous buildings.

Copper alloys include brass, bronze, aluminum bronze (90 percent copper and 10 percent aluminum), German silver (90 percent copper, 25 percent zinc and 25 percent nickel).

In 2008, copper was approved as germ killer by the U.S. government clearing the way for it to and copper alloys such as brass and bronze to be used on doorknobs, hospital fixtures and other products. Copper ions can penetrate the cell walls of microbes and disrupt reproduction and other cell functions. It has a 99.9 percent kill rate within two hours against the leading antibiotic-resistant bacteria.

Copper Producers and Copper Prices

The leading copper producers are: 1) Chile, 2) the U.S., 3) Poland, 4) Russia, 5) Peru, 6) Kazakstan, 7) Australia and 8) China. In 1988, the largest exporters were 1) Chile, 2) Zambia, 3) Canada, 4) Zaire and 5) Peru.

Production cost are about 65 cents a pound in the United States and 50 cents a pound in Chile, where the ore is richer. Phelps Dodge is the largest copper producer in the United States.

Copper prices collapses in the early 1980s. In the mid 1990s prices were high for three years until mid 1997 then they plummeted again reaching a low of 70 cents a pound in 2001. The rose over a dollar in 2003 and reached $1.35 a pound by May 2004.

The price of copper rose around 300 percent between 2000 and 2009 from around $2000 a ton to $6,000 a ton. The hike was fueled in part the construction boom in China and elsewhere in Asia that increased demand for copper to use in plumbing and utility wires. In April 2005, copper hit a record $7,040 per ton then reached $3.29 a pound, or $7,500 a metric ton in August 2006. In July 2008, copper reached a record peak of $8,920 a ton on worries about a mining strike in Peru.

The price of copper rose so high that in the United States thieves stole plumbing, air conditioners, utility wire, rain gutters and even bronze statues to get their hands on the copper to sell for cash. In California so much copper irrigation equipment was stolen that tomato and alfalfa crops were damaged.

The price of copper was so high that U.S. States coins using it were worth more melted down. With that the case U.S. mint officials prohibited melting down pennies. The penalty for doing so is up to five years in prison and a fine of up to $10,000. Modern pennies are 2.5 percent copper and 97.5 percent zinc. As of late 2006 the value of the metal in the coin was 1.12 cents. With production cost added in the value was 1.73 cents.

Copper Age

The 1,000-year-long Copper Age is also known as the Chalcolithic Period. It lasted from about 4500 B.C. to 3500 B.C., overlapping with the early Bronze Age. Some cultures and individuals used Copper Age technology after the Copper Age was over.

Copper was being fashioned into implements and gold was being fashioned into ornaments about 6,000 years ago, 3,000 years before the Greeks and Roman empires. Copper was the first metal to be worked by man on a relatively large scale in part because it is found in "large pure ingots in a natural state" in many different locations around the world. Axes, points and armor could be fashioned by simply hammering the metal; melting it wasn't necessary.

Some natural copper contains tin. During the forth millennium in present-day Turkey, Iran and Thailand man learned that these metals could be melted and fashioned into a metal---bronze---that was stronger than copper, which had limited use in warfare because copper armor was easily penetrated and copper blades dulled quickly. Bronze shared these limitations to a lesser degree, a problem that was rectified until the utilization of iron which is stronger and keeps a sharp edge better than bronze, but has a much higher melting point. [Source: "History of Warfare" by John Keegan, Vintage Books]

Making Copper in the Copper Age

Smelting ore probably began in China or India and made its way westward. Much of the copper in ancient civilization in Mesopotamia, the Middle East, Egypt, Phoenicia, Greece and Rome came from Cyprus, whose name is the source of the word copper.

To melt copper out the rock it is necessary to keep a fire at least 1981̊F (1083̊C). This was most likely done in ancient Copper Age sites by continuously blowing a fire through tubes made from wood, bamboo or reeds. Archaeologists recreating the process need about an hour of constant blowing to produced several copper pellets the size of BBs. Producing copper for an ax using this method would take several weeks.

Copper Age Settlements in the Middle East

Exposed rocks in western Jordan, in the Wadi Faynan region, contain bluish copper ore that can easily be removed my hand. Around 4500 B.C. people discovered that the copper ore, when heated to temperatures yields a metal strong enough to make tools as well as religious objects and other items. [Source: Katherine Oziment, National Geographic, April 1999]

The copper found in Wadi Faynan was moved along ancient trading routes from Jordan to Israel, mostly likely on foot and by donkey, to places like the Basheba Valley, where fertile alluvial soils along stream beds supported increasingly large populations.

A Copper Age village, with more than a thousand people and dated to 4200 B.C., was found in Shiquim in the Besheeba Valley in Israel in the 1970s. The people lived in mud brick and stone houses and built an extensive network of underground rooms used to store grain. Large structures used for religious, economic and social purposes were built.

Objects from Middle East Copper Age Settlements

In Copper Age Middle East Period people living primarily in what is now southern Israel fashioned awls, axes, adzes, chisels, vessels, mace heads, ornate standards, crowns and eight-inch rings (probably used as ingots because they were easy to transport and store). In a canyon called Nahal Mishmar on west side of the Dead Sea, archaeologists found 429 objects, dated to 3500 B.C., in reed mats that showed incredible artistry and technical skill.

People from the Chalcolithic Period also made objects from ivory and stone such as figures with large noses and breasts carved from hippopotamus and elephant tusk, violin-shaped figures made of schist, granite and limestone that may have been goddesses from a fertility cult.

In 1993, archaeologists found a skeleton of a Copper Age warrior in a cave near Jericho. The skeleton was found in a reed mat and linen ocher-died shroud (probably woven by several people with a ground loom) along with a wooden bowl, leather sandals, a long flint blade, a walking stick and a bow with tips shaped like a ram's horns. The warrior’s leg bone showed a healed fracture.

Bronze and the Bronze Age

Bronze is an alloy made of copper and tin.

The Bronze Age lasted from about 4,000 B.C. to 1,200 B.C. During this period everything from weapons to agricultural tools to hairpins was made with bronze (a copper-tin alloy). Weapons and tools made from bronze replaced crude implements of stone, wood, bone, and copper. Bronze knives are considerable sharper than copper ones.

Bronze is much stronger than copper. It is credited with making war as we know it today possible. Bronze sword, bronze shield and bronze armored chariots gave those who had it a military advantage over those who didn't have it.

The terms the Stone Age, Bronze Age and Iron Age were coined by the Danish historian Christian Jurgen Thomsen in his Guide to Scandinavian Antiquities (1836) as a way of categorizing prehistoric objects. The Copper Age was added latter.

Scientists believe, the heat required to melt copper and tin into bronze was created by fires in enclosed ovens outfitted with tubes that men blew into to stoke the fire. Before the metals were placed in the fire, they were crushed with stone pestles and then mixed with arsenic to lower the melting temperature. Bronze weapons were fashioned by pouring the molten mixture (approximately three parts copper and one part tin) into stone molds.

Typical Bronze Age food included round bread loaves, cheese, chick peas, garlic, goat, olives, and figs. People used stone and bronze sinkers, similar to ones they excavated, to weigh down fishing nets. Glass jars were made by wrapping liquid glass around a piece of clay that was dug out when the glass hardened. Ivory objects were painstakingly carved with drills propelled by a bow. Five-thousand-year-old bathing facilities were discovered in Gaza.

Tin and the Bronze Age

Copper tools had been around for long before bronze ones. Therefore the key ingredient that made the Bronze Age and innovation possible was tin. Copper was readily available over a large area. Much of it came from Cyprus. Tin was harder to find. It came mainly from mountains in Turkey and in Cornwall. Because tin was scarce and found in only localized regions, trade routes on which it was transported were set up. Tin itself became a highly profitable trade item. Taxes were placed on tin. Tolls were put in place on the trade routes.

In all likelihood Bronze Age Anatolians first got their tin from the Assyrians, who once referred to their Anatolian neighbors as "stupid,' in inscriptions from the second millennia B.C., because of the 100 percent profits they made by selling the Anatolians tin mined in the Hindu Kush mountains 1000 miles a way. Later the Anatolians found their own source of tin in the Tarsus mountains. Archaeologists discovered one six-square-mile area with nearly a thousand small tin mines. Some of the earliest mines, they say, were worked with stone tools by miners between the ages of 12 and 15. [Thomas Bass, Discover, December 1991.]

Later tin came from Cornwall. It was brought across the English Channel on boats and transported down the Somme, Oise and Seine Rivers into Europe.

World's First Bronze Age Culture

Bronze artifacts have been discovered in northern Thailand, around the village of Ban Chiang, that were dated to 3600 to 4000 B.C., more than a thousand years before the Bronze Age was thought to have begun in the Middle East. The discovery of these tools resulted in a major revision of theories regarding the development of civilization in Asia.

The first discoveries of early Bronze Age culture in Southeast Asia were made by Dr. G. Solheim II, a professor of anthropology at the University of Hawaii. In the early 1970s, he found a socketed bronze ax, dated to 2,800 B.C., at a site in northern Thailand called Non Nok Tha. The ax was about 500 years older than the oldest non-Southeast-Asia bronze implements discovered in present-day Turkey and Iran, where it is believed the Bronze Age began. [Source: Wilhelm G. Solheim II, Ph.D., National Geographic, March 1971]

Non Nok Tha also yielded a copper tool dating back to 3,500 B.C.. and some double molds used in the casting of bronze, dating back to 2300 B.C, significantly older than similar samples found in India and China where it is believed bronze metal working began. Before Solheim it was thought that the knowledge of bronze working was introduced to Southeast Asia from China during the Chou dynasty (1122-771 B.C.). Solheim is sometimes called "Mr. Southeast Asia."

Brass

Brass is an alloy made of copper and zinc. It is highly prized in making ornaments and decorative vessels and is also used in riveting, soldering and wire. The amount of zinc varies from 5 to 45 percent. Other metals such as aluminum, tin, led and manganese are added to resist corrosion, change the color or achieve some other property.

Copper has a higher melting point than zinc. It is usually melted first. The zinc is melted separately and is added in small pieces just before the molted metal is caste. Because the melting point of copper is higher than the boiling point of zinc about 5 to 10 percent of the zinc is lost to vaporization.

Bronze can be cast in molds or shaped by machines that draw, press, stamp and spin the metal into finished articles. Brass is often spun like pottery on a wheel and decorated with a burnishing tool on a lathe. A thin layer of brass can be applied to iron and steel by electroplating.

Brass is made into lamps and cases and other objects by skilled craftsmen in India and the Middle East.

Image Sources: Wikimedia Commons

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.

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© 2008 Jeffrey Hays

Last updated August 2012

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