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Gold/Mining/Energy : Pacific Rim Mining V.PFG -- Ignore unavailable to you. Want to Upgrade?

To: charred who wrote (12321)	11/20/1999 10:33:00 AM
From: Bill Jackson	Read Replies (1) \| Respond to of 14627

charred, With a tight seamless rock, like quartzite you need to find an exposed bit of metal for the leach fluid to remove that entire bit. Quartzite, as the name implies, is glasslike and when you crush the rock you will need more crushing to a smaller size to make sure you expose 90%+ of the gold grains to the leach liquid. Alkali helps this as it does attack quartz slowly. Quartzite can also be very tough to grind and this extra energy to girnd it is a cost that needs to be determined by grinding tests. Suphidation also has a tendency to encapsulate gold grains in iron/arsenic pyrite shells that are immune to the leach fluid and they need to be oxidised by a furnace or a autoclave or by a bacterial oxidation stage in a heap leach. The grade determines the approach as costs vary with leach being the cheapest, slowest and lowest efficiency. Often sulphide rocks need a flotation stage to concentrate the gold bearing sulphide particles because they are what needs the oxidation and there is no point in wasting heat and furnace time on barren rock. Bill