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According to Pliny, the mineral stibnite was found most commonly among silver ores.Pliny described how stibnite could be used as a medicine and how, if heated too strongly, it would turn to lead.People who drank over 19 ppm of antimony in one sitting vomited. Antimony also has the unusual property that (like water) it expands as it freezes.Antimony’s electrical and thermal conductivity are lower than most metals’ conductivities. Four other elements expand when they freeze; silicon, bismuth, gallium and germanium.This confidence is provided by an 'assay' (test and assess) of the precious metal content of that item.It is impossible to tell the precious metal content of any item simply by looking at it.Antimony alloys are therefore used in making typefaces for clear, sharp printing.Babbit metals, used for machinery bearings, are alloys of lead, tin, copper and antimony.
Most metals are metallic grey or silvery white whereas gold is characteristically a metallic yellow colour, in other words gold-coloured. The gold colour seems related to relativistic effects of the outermost gold orbitals.
Gold is found in sea water, but no effective economic process has been designed (yet) to extract it from this source.
Gold Assay It is critical from the public's perspective that there is confidence in the claimed purity of any particular item made from precious metals.
Remarkably other colours such as purple (a gold:aluminium alloy), blue (a gold:indium alloy) and even black (a gold:cobalt alloy) may be formed.
Gold is usually alloyed in jewellery to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold).