 Occurrence
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| Native lead does occur in nature, but it is rare. Currently lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6% lead. Other common
varieties are cerussite (PbCO3) and anglesite (PbSO4). The largest current source of lead, however, is recycling, primarily of automobile batteries.
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| In mining, the ore is extracted by drilling or blasting and then is crushed and ground. The ore is then treated using extractive
metallurgy. The Froth flotation process separates the lead and other minerals from the waste rock (tailings) to form a concentrate.
The concentrate, which can range from 50% to 60% lead, is dried and then treated using pyrometallurgy. The concentrate is
sintered before being smelted in to produce a 97% lead concentrate. The lead is then cooled in stages which causes the lighter
impurites (dross) to rise to the surface where they can be removed. The molten lead bullion is then refined by additional
smelting with air being passed over the lead to form a slag layer containing any remaining impurities and producing 99.9%
pure lead.
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| Lead ore (galena) is found commonly in north-east Wales. The North-east Wales Orefield was by far the most important source
of lead and zinc in Wales and second in national importance only to the North Pennine Orefield. Lead mining dates back to at least Roman times
and continued until well into the 20th century. Galena can be found today in the spoil heaps associated with mining activity.
Galena is present in steeply-dipping fissure veins and in pipes and is in Mississippi Valley-type lead-zinc-fluorite and copper-dolomite
associations. The mineralisation occurs in the upper parts of the Loggerheads and Cefn Mawr Formations of the Carboniferous
Limestone.
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| In 2005, China produced almost one-third of the global mined output of lead closely followed by Australia. |
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