Senin, 24 Januari 2011


makeit yourring engagement rings Gold, recognizable by its yellowish cast, is one of the oldest metals used by humans. As far back as the Neolithic period, humans have collected gold from stream beds, and the actual mining of gold can be traced as far back as 3500 B.C., when early Egyptians (the Sumerian culture of Mesopotamia) used mined gold to craft elaborate jewelry, religious artifacts, and utensils such as goblets.

Gold's aesthetic properties combined with its physical properties have long made it a valuable metal. Throughout history, gold has often been the cause of both conflict and adventure: the destruction of both the Aztec and Inca civilizations, for instance, and the early American gold rushes to Georgia, California, and Alaska.

makeit yourring engagement rings. The largest deposit of gold can be found in South Africa in the Precambrian Witwatersrand Conglomerate. This deposit of gold ore is hundreds of miles across and more than two miles deep. It is estimated that two-thirds of the gold mined comes from South Africa. Other major producers of gold include Australia, the former Soviet Union, and the United States (Arizona, Colorado, California, Montana, Nevada, South Dakota, and Washington).

About 65 percent of processed gold is used in the arts industry, mainly to make jewelry. Besides jewelry, gold is also used in the electrical, electronic, and ceramics industries. These industrial applications have grown in recent years and now occupy an estimated 25 percent of the gold market. The remaining percentage of mined gold is used to make a type of ruby colored glass called purple of Cassius, which is applied to office building windows to reduce the heat in the summer, and to mirrors used in space and in electroscopy so that they reflect the infrared spectrum.

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Because gold is a finite resource, its long-term future is limited. In the short term, however, it will continue to find widespread use in jewelry and in industrial applications, especially in the electronics field.
In the last few years, several companies have focused on extracting gold from sulphide ore rather than oxide ore. Previous techniques made such extraction difficult and expensive, but a newer technique called bioleaching has made extraction more feasible. The process involves combining the sulphide ore with special bacteria that "eat" the ore or break it down into a more manageable form.Gold

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