INTERESTING HISTORY: Desert Gold: Part I

By the end of the 19th century, large mechanized stamp mill operations with 100 stamps or more would work around the clock pulverizing ore. The finely rendered material was washed down onto mercury-coated copper plates that bonded with the gold as it passed over but could only recover about 60 percent of the metal. The plates were then roasted thus releasing the gold. Although the cyanidation process would begin to replace the use of toxic mercury for gold recovery during the 1890s, the amalgamation method remained in continual use through the 1960s when it was banned for such purposes through the 1976 Toxic Substances Control Act[vi][vii].
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