Almost all world trade is made of gold ingots, weighing about 12.5 kg and with a purity of 99.5%.The unit of exchange is the troy ounces and the carat is used to measure the purity. According to these standards is 24 carat pure gold, +100% ie 24/24. Pure gold is 50% 12/24 or as shown as gold 12 carat gold. The gold is very soft and therefore can not be used in its pure state. It is usually alloyed with other metals: copper, zinc, silver and nickel.
About 80% of world production is concentrated in just two countries: South Africa and Russia. The use of gold industry accounts for less than 10% of total production and covers applications in electrical and electronic equipment.
Makes as well in jewelry, gold being a soft metal, is associated with other metals for durability. The relationship between the amount of gold and other metals in the alloy is called title (expressed in thousands/gram). The most commonly used alloys are:
- yellow gold: alloyed with silver and copper;
- pale yellow gold: copper alloy with very little silver;
- rose gold: alloyed with copper and very little silver;
- red gold: alloyed with copper;
- white gold: alloyed with palladium;
- green gold: alloyed with silver;
- lilac gold: alloyed with aluminum;
- blue gold: alloyed with cobalt.