SIC 1041 Gold Ores

SIC 1041

This category covers establishments primarily engaged in mining gold ores from lode deposits or in the recovery of gold from placer deposits by any method. In addition to ore dressing methods, such as crushing, grinding, gravity concentration, and froth flotation, this industry includes amalgamation, cyanidation, and the production of bullion at the mine, mill, or dredge site.

NAICS CODE(S)

212221

Gold Ore Mining

INDUSTRY SNAPSHOT

Mined on every continent except Antarctica, gold is used for a wide variety of applications ranging from jewelry and the arts to dentistry, electronics, and diverse industrial applications. In 2004 U.S. gold mine production was valued at approximately $3.2 billion. Of that amount, jewelry and other art-related pursuits accounted for 92 percent of U.S. gold consumption, dental use for 3 percent, and electronics for 4 percent, according to statistics from the U.S. Geological Survey. As a precious metal, gold is traditionally used as a backing for paper currency systems and as a hedge against inflation. Of all the gold produced by the United States in 2004, more than 99 percent came from 30 mines.

An estimated 150,000 tons of gold make up the world's resources, according to the U.S. Geological Survey. South Africa has one half of this total. Brazil and the United States each have 9 percent. Other major producers include Australia, Canada, Russia, China, and Peru. Of the 128,000 tons of total mined gold, approximately 32,000 tons are held by central banks as official stocks. The remaining 96,000 are held privately as coin, bullion, and jewelry.

BACKGROUND AND DEVELOPMENT
A Shining Past

Its sparkling character, beautiful hue, and unique metallurgical properties—including resistance to tarnishing and corrosion, and virtual indestructibility—have set gold on the throne of coveted precious metals since early history. Ancient Egyptian, Minoan, Assyrian, and Etruscan artists produced elaborate gold artifacts as early as 3000 B.C. As increasingly complex economic systems evolved, gold was used as a high-denomination currency and eventually as a backing for paper-currency systems.

The Source

Naturally occurring gold is dispersed throughout the earth's crust and is usually combined with other elements such as silver, copper, platinum, and palladium. In addition, small amounts of gold are usually recovered as a by-product in the refining of such base metals as copper and lead. Gold ores, large and rare masses of rock that are very rich in the metal, are usually quartz lodes (also called veins) or deposits that fed off of river bed gravel or quartz conglomerate beds (termed blankets or reefs). One of the best-known reefs is the South African Witwatersrand system in the Transvaal and Orange Free States. Though gold occasionally appears in rock formations as visible flakes, grains, or nuggets, it remains for the most part invisible until separated from ore and refined. The principal ores are calaverite, a telluride (containing tellurium) containing 40 percent gold, and sylvanite, a mixture containing 28 percent gold and variable amounts of silver.

Mining History

Ancient Near Eastern civilizations made profitable use of gold culled from alluvial deposits in and along streams. Egyptian monuments dating back to the first dynasty (c. 3100 to c. 2890 B.C.) depicted the washing of gold ores. Gold deposits were also exploited throughout regions including the Aegean, Libya, Persia (later Iran), India, and China. By the Middle Ages in Europe, gold was mined in Saxony and Austria and, to a lesser extent, Spain.

With the European colonization of the Americas in the sixteenth century, gold production reached unprecedented levels, as output from mines worked by slaves was supplemented by hoards taken from native palaces, temples, and burial sites. Well into the seventeenth and eighteenth centuries, South American mines accounted for the majority of world gold production. In the early nineteenth century, massive deposits were uncovered in Russia, making it a world leader in gold mining from the 1820s to the late 1830s.

The discovery of gold in California and Australia in the mid-nineteenth century brought a veritable explosion of gold production. Prospectors flocked to California to participate in the gold rush of 1849, earning themselves the name "49ers." From 1890 to 1915, world production of gold jumped again, with major developments in Alaska, Yukon Territory, and South Africa, as well as Canada in the 1920s. In the early twenty-first century, primary production of gold was carried out in South Africa, Australia, Brazil, Canada, the United States, and several republics of the former Soviet Union, now the Commonwealth of Independent States (C.I.S.). Although gold markets became increasingly convoluted, steady advances in mining and refining technology—such as the development of the heap-leach process in the mid-1980s—continued to increase efficiency and permit mining of less accessible and lower-grade ores.

Mining

Gold is recovered by three basic mining methods: placer mining of alluvial deposits, lode or vein mining, and recovery as a by-product of base-metal mining. In placer mining, the oldest method, the high-density gold is separated from the lighter, siliceous material (called the matrix or gangue) in which it is found. Though the basic principles of placer mining are essentially the same, methods of varying sophistication were developed according to the scale of particular mining operations and the types of terrain exploited. The simplest method of placer mining, practiced by the individual miners in the great American gold strikes of the nineteenth century, was panning—a technique by which several handfuls of siliceous material were placed in a pan or batea (a wooden bowl for washing gold that was commonly used in Mexico) and repeatedly washed with large amounts of water until the denser materials, including gold, were left at the center of the pan. To "sift" greater amounts of material, cradles (also called rockers) were developed in which material was "rocked" with the aid of water, and dense materials were collected in riffle. Pieces of wood or iron were perpendicularly attached to the bottom and sides of the cradle.

Several other large-scale placer methods are used as well. In hydraulic mining, powerful jets of water are directed at thick beds of gravel to break them down and wash the residue through lines of sluices designed to separate gold particles. The subsequent discarding of large amounts of residue into adjacent rivers and farmlands, however, resulted in injunctions in America that limited the practice after 1880. Large-scale placer mining continued to develop, however, with the late nineteenth-century invention of the gold-mining dredge in New Zealand. Originally used in the rivers of New Zealand, California, and Russia, the dredge technique later evolved into the paddock dredge, developed in the western United States. Here, this technique...

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