The chemistry of gold extraction / Химия поведения золота

Many of the methods now used for gold extraction are based on techniques that have been known or established for centuries. Gravity concentration, amalgamation, cyanide leaching, chlorination, zinc precipitation, and carbon/charcoal adsorption are all processes that have been used for at least a hundred years, and combinations of these remain as the basis for most gold recovery flowsheets. The ingenuity of the early pioneers in developing technology with such longevity is admirable. On numerous occasions over the years, rediscovery or reevaluation of this technology has led to its commercial redevelopment, while incorporating the advantages of contemporary improvements. Consequently, it is important to know the historical background of gold extraction processes and technology, as it may well help to shape the future.
The predominance of cyanidation as the principal gold extraction technique since the late 19th century and the commercial acceptance of other important hydrometallurgical processes, such as heap leaching and carbon adsorption in the 1970s and 1980s, naturally divides the history of gold extraction into four main eras:
 Precyanidation: pre-1888
 Cyanidation: 1889–1971
 Era of major technological development: 1972–2000
 Into the 21st century
The key dates in this categorization are the initial application of cyanidation and zinc precipitation in 1889 and the boom in new technology, which started in 1972, when the price of gold was disengaged from its official selling price and allowed to move with market forces. <...>