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Strategies & Market Trends : Winter in the Great White North -- Ignore unavailable to you. Want to Upgrade?

To: IngotWeTrust who wrote (2682)	8/2/2002 3:05:14 PM
From: E. Charters	Read Replies (1) \| Respond to of 8273

Did you know that gold is "magnetic"? True story. If you pass a magnetic field underneath a flake of gold, it will be attracted to the magnet and "jump". It is the same principle as the AC induction motor, or the street car brake, which uses a magnet brought near a rotating copper plate to retard the car. The key is the magnet, or the field, or material must be moving. This is sometimes seen where a search coil will get a signal in some materials when you move the coil, or move the rock, but not when they are both standing still. This principle is often used in geophysics where the coil has a rotating field, or the field will lock into a conductive body if the amplitude or frequency of the generated field is changed. (the field will in effect "move" if it changes amplitude or frequency..) The principle of eddy current induction in a conductive body can be used to differentiate gold on a table and one outfit in the States advertises that its table can separate black sands from gold by this effect. They utilize a rapidly polarity-reversing magnetic field underneath the table that is supposed to make the gold grains react and take a different path than the magnetite and other grains. I have seen this underlying idea work without the polarity reversal in a patented device that had a static magnet and would create an attraction in grains that moved over it, that were conductive but not magnetic. It was used to separate and concentrate hematite, which is a conductive, but not magnetic iron ore. If you had gold in quartz sand, you could effect a separation by placing the sand on a paper in a monolayer and moving a magnet quickly below the paper while vibrating it. A little bit of a hard trick, I will admit. A thin vibrating table that jiggled the sands in one direction but had a magnet underneath it would suffice to do the same thing. The gold would hold back as it passed over the magnet, and if washed in one direction would separate in path from the other sands. EC<:-}