Radioisotopes in carbon dating
While there are assay offices in the USA, there is no hallmarking scheme.Cartoon by Nick D Kim ([Science and Ink], used by permission).It is impossible to tell the precious metal content of any item simply by looking at it.Precious metals such as old, silver, and platinum are too soft to use alone for making jewellery, cutlery and other goods.Addition of some copper gives "rose gold", a soft pink colour.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.
There has been an "Assay Office" at Sheffield in England since 1773 when local silversmiths won the right from Parliament to assay silver in Sheffield.
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.
Small amounts of other metals alloyed with gold change the colour as well as mechanical properties such as hardness.
It is a good conductor of heat and electricity, and is unaffected by air and most reagents.
Gold is readily available commercially and its price changes day by day and is one of the most widely tracked commercial prices.
Search for radioisotopes in carbon dating:
The 1773 Act of Parliament appointed 30 local men as 'Guardians of the Standard of Wrought Plate in the Town of Sheffield' to supervise the work of the Office.