Gold has seduced the world with its beauty, but also because not even acid can alter its natural properties. An estimated 130,000 tons have been extracted from the earth since prehistoric times, of which 100,000 tons in the twentieth century alone. Gold is a malleable substance (with a hardness of just 2.5) and therefore easy to work with. It can be used in an alloy with other metals, often silver and copper. These alloys increase its resistance and change its colour.
Contains: For 750 gold, approximately:
- Yellow gold: 12.5% silver - 75% pure gold - 12.5% copper
- Pink gold: 6% silver - 19% copper - 60% pure gold - 10% palladium - 5% nickel
- Red gold: 5.5 % copper - 94.5% pure gold
- White gold: 10% copper - 10% palladium - 5% nickel - 75% pure gold
- Blue gold: an alloy of gold and iron. Heat treatment oxidizes the iron molecules at the surface of the metal, producing the blue colour.
- Green gold: an alloy of gold, silver and copper.
- Black gold: obtained by means of chemical vapour deposition (similar to PVD) of atoms of gold, carbon and other metals. The black coating is just a few microns thick. Other surface treatments use electrodeposition of rhodium, chromium and very dark impurities.
- Brown gold: obtained by heat treatment.