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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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L
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Lead_ore
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INFOTEXT
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1992-09-03
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Any of several minerals from which lead is
extracted. The main primary ore is galena or
lead sulphite PbS. This is unstable, and on
prolonged exposure to the atmosphere it
oxidizes into the minerals cerussite PbCO3
and anglesite, PbSO4. Lead ores are usually
associated with other metals, particularly
silver - which can be mined at the same time
- and zinc, which can cause problems during
smelting. Most commercial deposits of lead
ore are in the form of veins, where hot
fluids have leached the ore from cooling
igneous masses and deposited it in cracks in
the surrounding country rock, and in thermal
metamorphic zones, where the heat of igneous
intrusions has altered the minerals of
surrounding rocks. Lead is mined in over 40
countries, but half of the world's output
comes from the USA, the USSR, Canada, and
Australia.