Silver usually occurs in massive form as nuggets
or grains , although it may also be found in wiry, dendritic
(tree-like) aggregates. When newly mined or recently polished,
it has a characteristic bright, silver-white colour and metallic
lustre.
However, on exposure to oxygen in the air a black layer of silver
oxide readily forms, tarnishing the surface. Because of this,
and the fact that it is too soft to be used in most jewellery
in its pure form.
Most silver is a by product of lead mining, and is often associated
with copper. The main silver mining areas of the world are South
America, the USA, Australia, and the former USSR. The greatest
single producer of silver is probably Mexico, where silver has
been mined from about AD 1500 to the present day.
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