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Subsequent History Of Gold-: However, the number of surviving examples of gold- and silverwork from the Middle East declines after the triumph of Islam. Only in Christian Europe do examples remain from all periods after the fall of Rome. From before about 1650 A. D., principally religious pieces survive; after that time, sufficient religious and secular pieces survive for the reconstruction of the subsequent history of gold- and silverwork.
The gold in these deposits is found in small grains of irregular outline. There is some controversy as to the origin of the deposits. The gold grains appear to be too irregular to be of placer origin, and yet the host rock is placerlike in appearance. It is now widely believed that the deposits represent a placer that has been extensively altered by hydrothermal solutions.
The gold-bearing reef extends from the surface in some areas to far below subsequent overlying deposits in others. Most of the surface gold has been removed, and gold in this area is now obtained from deep underground mines.
Recovery of By-product Gold. Smelting processes in the base metal industry carry gold and other precious metals along with the desired product up to the final refining process; hence, the precious metals are concentrated as by-products. Subsequent to the final refining the wastes are treated, usually electrolytically, for the recovery of gold, platinum, palladium, and other metals. |
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