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Gold/Mining/Energy : Crystallex (KRY) -- Ignore unavailable to you. Want to Upgrade?

To: RMF who wrote (7091)	3/19/1998 8:51:00 AM
From: Bill Jackson	Read Replies (1) \| Respond to of 10836

Chief, The smaller you crush it the faster it leaches. We leach most gold as we grind it finelt to 200+ mesh. Take only a short time. As the graisn get bigger the leach slows and the end point is less gold extracted, but a lower crushing cost. It also depends on the porosity of the grains, if they are sulfided, and other things. You cannot grind to 200+ mesh and heap leach as the percolation through the pile would stop(blocking). Often they heap leach with a size like aquarium gravel or bigger and then stretch the time parameter. If you have solid granite with 1 grams per ton, forget it, low permeability would leave the gold locked up inside the grains for centuries(1 MM leach/1000 years for granite). So you can find uneconomic rocks at 1.5 g/ton for heap leach. For on surface stuff even hard granite rock can be ground down to 200+ for gold. The break even is around 2 for big open pits. the rippable porous stuff they heap leach in Nevada is leachable well under a gram per ton. It can be mined with giant claws they drag across the ground(rippers) and it crumbles readily and they screen it and crush it with low energy and then let it leach. Bill