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Gold/Mining/Energy : Gold Price Monitor -- Ignore unavailable to you. Want to Upgrade?

To: Richnorth who wrote (82768)	3/2/2002 9:46:00 PM
From: E. Charters	Respond to of 116795

The Queychua used to mine the salts on the Nazca plain and combined them in equal proportions with their placer gold concentrates that presumably contained an appreciable amount of sulphides. They heated them to low temperatures for about 5 days and then limed the acid solution to neutral pH. Then the heaped scrap copper in the solution which was freshly scratched. This last step is important as electrolytic "loops" form at the scratches much like they do when iron rusts. For a brief period the solution is boiled and the gold and silver plate out on the copper. Then the copper is scraped and the gold smelted. I have tried this method. I used about 30% of the concentrate wieght in salts in equal parts and added equal water to the mixture to a sulphide rich concentrate. I added a tincture of battery acid to promote the starting of the reaction. In about 24 hours the reaction was complete at room temperature. Scratched copper put in the solution after careful sodium bicarb neutralization soon became encrusted with a brown precipitate that when smelted in the usual way with flux did yield a gold button. The gold was free from a pan concentrate of an ore zone. The method was described as a recent discovery in Scientific American in the late 1980's. The salts are available in any drugstore and are not restricted. The method was economical for the Nazca people as the salts were plentiful in that area to mine. Also the volume of their concentrate was small, and the hand labour it required for treatment was readily available. There are modified forms of this dissolution and recovery technique proposed by various research groups. It should be noted that chloride dissolution only suffers in comparison to cyanide, which replaced it in 1896, with respect to its incomplete breakdown of sulphides which are refractory, and the poorer methods of precipitation of the gold that were available. Chloritization was usually a "furnace" or hot bath method and had low recovery and throughput at the time. Chlorides of roasted cons also tended to pick up large quantities of other metals as well and the precipitation could not be restricted to gold. These drawbacks are being worked on with methods as diverse as targeted CIL, microwave burst and carbon aerogel technologies, all no doubt with attendant patent recovery schemes of pennies on the dollar. The race to replace cyanide plods on, with dire threats of gold's imminent demise as a money metal hanging ever more gloomily on the horizon. EC<:-}