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Gold/Mining/Energy : International Precious Metals (IPMCF) -- Ignore unavailable to you. Want to Upgrade?

To: BillyZoom who wrote (32442)	5/27/1998 1:18:00 PM
From: go4it	Read Replies (2) \| Respond to of 35569

Robert, Have you ever seen a writing like this? It is an excerpt from an article that I found. Biotechnology is considered one of the three key technologies of the decade. For over 100 years gold has been recovered by way of the so-called McArthur Forrest process. This, in its simplest form, essentially involves grinding the ore to a fine slurry and dissolving the gold in a solution of sodium cyanide. Recovery out of solution is achieved either by reducing it back to the metallic state and precipitating it on particulate zinc or by adsorbing it onto granulated activated carbon. Ores amenable to this simple form of processing are generally termed "free-milling". This in essence means that the particles of gold encapsulated in the host rock, being relatively large, are liberated by simply grinding to a top size of only 160 micrometres, as is with the reefs of the Witwatersrand Basin in South Africa. In other parts of the world it is not as simple. These gold deposits, termed hydrothermal, are pyritic and often contain appreciable quantities of arsenic as arsenopyrite; obviously a major environmental hazard. Gold associated with these deposits is extremely fine and generally occluded in the crystal structure of the sulphide minerals. No amount of grinding will liberate the metal. For example, at a grind size typical of that used on the Witwatersrand, yields of only 30 percent, sometimes as low as 6 percent, are obtained. Only with the destruction of the pyritic minerals can all the gold be released and an acceptable recovery achieved.