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(More customer reviews)"Gold Mines" presents an overview of gold-mining history, as well as current underground vs. open-pit mining.
South African gold mines pursue both the world's richest veins and do so at the deepest levels - 2 miles. Mine temperatures reach 128 degrees w/o cooling, 96 degrees with - at 100% humidity. (A mine cooling system could instead cool a city of 100,000 people.) Tunnel facings at that depth are under tremendous pressure and sometimes explode. Miners take ten minutes descending down the mine elevator to get to their work depth; explosive methane gas is also sometimes a problem. Mining engineers, meanwhile, are considering even deeper gold mines, probably to be worked by robots.
Early History: The oldest evidence of gold processing was recently found in Bulgaria - 6,000 year-old sold gold figures. Egyptians created the first underground mines. Peruvians created early gold-plating.
Early mining improvements included use of horses to move underground ore, use of water-powered wheels to power hoists.
Early expeditions to the U.S. and the New World were all motivated by gold. Until 1799 gold mining was done for king and country; after the 1799 gold discovery in North Carolina (17-lb. nugget), gold mining became a matter of personal enrichment.
U.S. mining began as placer mining, then moved underground when the easy sources played out. The Sutter's Mill strike in California brought miners from all over the world.
Hydraulic mining of river banks created large-scale pollution and was banned in California in 1884. The 1850 Comstock Lode mine discovery led to square beam supports for interior walls and the devastation of large sections of forest. Comstock Lode miners took a break every half-hour and were allotted 95 pounds of ice/day.
Compressed-air drills allowed much faster progress, but were also known as "widow-makers" because dust created led to serious lung diseases. Fortunately, water was added to the drills about ten years later.
The Alaskan/Yukon Gold rush of 1896 quickly played out the rich ore, leaving low-grade (1 oz./22 tons) requiring crushing, stamping, and refining with mercury and cyanide.
Deregulating the price of gold in 1968 led to new vast open-pit mines and refineries that profitably processed ore for the 1 oz./45 tons of ore, and cost $200,000-$1 billion to create.
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