Precious Metals - Pierre DeRoche PDR 4018 Royal Retro Mode D'emploi

Precious metals

The precious metals most used in watchmaking and jewellery are
gold and platinum. Gold has the specific property of being entirely
stable, as well as malleable and ductile (meaning it can be drawn
out with breaking). Gold is not used in its pure state (999.9/1000
or 24-carat standard of fineness), but is instead alloyed with other
metals so as to lessen its malleability and to modify its colour.
The gold alloys used in watchmaking and jewellery are thus
composed of 75% gold and 25% other metals.
These other metals are copper, silver and palladium, in
proportions varying according to the desired colour.
• Yellow gold: 75% gold, 16% silver, 9% copper
• Rose gold: 75% gold, 5% silver, 20% copper
• White gold: 75% gold, 4% silver, 4% copper, 17% palladium
As far as terminology is concerned, the word "gold" is reserved
for alloys with standards of fineness corresponding to 0.916 (22
carats) and 0.750 (18 carats). As for platinum, the alloy used in
watchmaking and jewellery is composed of platinum (95%) and
palladium (5%).
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