Gold production

In the United States, about 90% of gold production originates from ores and placer deposits. The remainder is recovered primarily as a by-product of the refining of base metals, chiefly copper. The principal gold producing states are Nevada (60%) and Califomia (10%) followed by Montana, Utah, S. Dakota, Washington, Colorado, Alaska, Idaho, Arizona, and New Mexico (7). 

A second separation technique is leaching, which uses solubility properties to separate the components of an ore. For example, modem gold production depends on the extraction of tiny particles of gold from gold-bearing rock deposits. After the rock is crushed, it is treated with an aerated aqueous basic solution of sodium cyanide. Molecular oxygen oxidizes the metal, which forms a soluble coordination complex with the cyanide anion ... 

The total production of gold, silver and other associated base metals and silver/ gold production ratios from these deposits are summarized in Table 1.17. In addition to gold and silver, lead, zinc and manganese have been produced from some of the Se-type (e.g., Yatani) and copper has been produced from some of the Te-type (e.g., Teine, Kawazu). Total tonnage of production of Au and Ag from the Se-type is greater than... 

Mercury is mined predominantly as HgS in cinnabar ore and is then converted commercially to a variety of chemical forms. Key industrial and commercial applications of mercury are found in the electrolytic production of chlorine and caustic soda the manufacture of electrical equipment, thermometers, and other instruments fluorescent lamps dental amalgam and artisanal gold production. Use in pharmaceuticals and in biocides has declined substantially in recent years, but occasional use in antiseptics and folk medicines is still encountered. Thimerosal, an organomercurial preservative that is metabolized in part to ethylmercury, has been removed from almost all the vaccines in which it was formerly present. Environmental exposure to mercury from the burning of fossil fuels, or the bioaccumulation of methylmercury in fish, remains a concern in some regions of the world. Low-level exposure to mercury released from dental amalgam fillings occurs, but systemic toxicity from this source has not been established. 

The following procedures have been described in the literature as being useful for colloidal gold production ... 

It may indeed sound romantic, but it is a fact that both in 1970 and 1971 at least 500 tons of gold—that is to say half of all South Africa s production, or 40 percent of total gold production in the non-communist world—passed through unofficial channels on the way to its ultimate destination."... 

Emission of Hg from gold production. Nriagu and Pacyna (1988). 

Benzo-1,4,8,11-Tetrathiacyclopentadecane)rhodium(I) Hexafluorophosphate, [Rh(TTX)]PFo. To a solution of 0.5 g [Rh-(TTX)Cl2]Cl 3.5H2O in 50 ml dry, deaerated methanol was added 0.15 g sodium borohydride dissolved in 5 ml methanol. Excess (2-3g) NH4PFG dissolved in 10 ml methanol was then added to the gold solution. The brown-gold product crystallized out of solution and was collected on a filter frit and dried on a vacuum line in the glove box. 

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