The mining industry locates valuable minerals in the earth and water and removes them in the most economical and efficient way. Mined materials include energy minerals, such as coal, petroleum, and uranium; nonmetallic minerals, such as limestone, salt, sandstone, and diamonds; and metallic minerals, such as iron ore, gold, and silver.

Mining is the discovery, valuation, development, exploitation, processing, and marketing of useful minerals. Although early humans used exposed minerals for tens of thousands of years, the earliest mine did not appear until approximately 8000 B.C. At that time, humans extracted clay for cooking ware, hard volcanic rock for plowing, gold for ornamentation, and flint for basic weaponry. By 3000 B.C., humanity had entered the Bronze Age, mixing tin and copper to produce weapons and utensils that were stronger than flint. Humans had begun to use iron by 1200 B.C. During the Iron Age, humans mined valuable materials. Ceylon and India mined gems for trade, and the Greeks cut marble for their magnificent structures.

The usefulness of bronze, tin, and iron led to the development of more sophisticated mining techniques, which culminated during the Roman Empire. In addition to metals, the Romans mined volcanic ash, combining it with other materials to create very durable cement. For more than 1,000 years after the end of the Roman Empire, mining techniques remained stagnant. It was not until the 1400s that the French, Germans, and Swedes began mining their territories with vigor.

Mining did not take hold in the United States until the 1700s, when French explorers discovered rich lead and zinc mines in the Mississippi River Valley. In the mid-1800s, Pennsylvania residents developed numerous coal and coke mines, giving rise to the famous millionaires of the Gilded Age in U.S. history: Andrew Carnegie, Henry Clay Frick, Andrew Mellon, and John Pierpont Morgan. Such cities as Pittsburgh, Pennsylvania; Gary, Indiana; and Duluth, Minnesota grew rapidly, increasing the country's industrial and economic strength. At the same time, the discovery of rich oil fields in Texas introduced an entirely new industry to the country.

After World War II, the United States entered the nuclear age, mining rare radioactive materials for nuclear energy and weaponry. More recently, the U.S. mining industry has experienced its share of ups and downs. Facing intense competition from abroad, the industry has had to make many technological improvements to compete with other countries.

Many mining companies concentrate on just one or two facets of the industry; others provide special services to mining companies. For example, some companies perform just the drilling and sampling phase of prospecting and exploration. Similarly, some only analyze samples for mineral content.

A number of small and intermediate-sized mining companies produce from 100 to 500 tons of ore per day and have a labor force of 25 or less. Whereas the general methods of development and exploitation remain the same, the small and intermediate companies usually do not have the extensive capital resources to purchase the many types of equipment needed for larger operations.

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