Gold is almost indestructible and has been used and then reused for centuries to the extent that all gold of known existence is almost equal to all the gold that has ever been mined. It is claimed that all gold mined since the dawn of history would fit into a 100 foot cube. Gold is almost completely resistant to air, water and acids, and can be dissolved only by a very strong acid called aqua regia. Gold is a great medium metal for jewellery, as it never tarnishes. Pure (fine) gold is yellow in colour. It is the most malleable and ductile of all metals. Gold can be made so thin that a stack of 10,000 gold leaves is only 1mm thick, and one ounce of gold can be drawn into a wire 35 miles long. Gold is almost always alloyed with other metals to increase strength, lower melting point and reduce cost. By changing the alloys or "ingredients" the colour can be changed to make white and red gold. In the case of white gold, palladium and nickel are added to whiten the metal. The best quality white gold contains palladium (a precious metal in its own right and a member of the platinum group) and is therefore the most expensive of the gold alloys. The percentage of fine gold used determines the carat (or karat in America) of the gold. The gold content of 18ct is 75%, 14ct - 58.5% and 9ct - 37.5%. |   |