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Extraction of Metals

Alloys - containing Gold.

Pure gold is very soft. Gold is mixed with silver and copper
in different amounts to make an alloy which is harder and stronger.

The percentage of gold in an alloy is measured in carats or fineness.
100% pure gold is 24 carats, 75% gold is 18 carats
50% gold is 12 carats and 37.5% gold is 9 carats.
The available percentage of gold in jewellery
is different in different countries. In the UK you can
get 22 carat, 18 carat,14 carat and 9 carat gold jewellery
but not 12 carat gold jewellery.

Fineness is the amount of gold in parts per thousand
so 100% pure gold has a fineness of 1000
75% gold has a fineness of 750
50% gold has a fineness of 500
and 37.5% gold has a fineness of 375.

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