Gold is a precious metal that has been valued by people since ancient times.

Gold is a very soft metal when it is pure (24 Kt. is pure gold). It is usually alloyed (mixed with other metals, often silver and copper) to make it harder, but less expensive.

The scientific abbreviation of gold is Au. The purity of gold jewelry is measured in karats. Some countries hallmark gold with a three-digit number that indicates the parts per thousand of gold. In this system, "750" means 750/1000 gold (equal to 18K); "500" means 500/1000 gold (equal to 12K).

Karat Percent Gold
24 Kt. 100% Gold
18 Kt. 75% Gold
14 Kt. 58.3% Gold
12 Kt. 50% Gold
10 Kt. 41.7%

24 karat gold is pure gold. 18 karat gold is 18/24 gold (about 75% gold - three quarters gold). 14 karat gold is 14/24 gold (about 58% gold - a little over half gold). 12 karat gold is exactly half gold. 10 karat gold is 10/24 gold (only about 43.5% gold - less than half gold).

Alloyed gold comes in different colors:
Colored Gold Alloy Metal(s) Added to the Gold
Yellow Gold 50% silver and 50% copper
White Gold Nickel, zinc, copper, tin and manganese
Pink (rose) Gold 90% copper and 10% silver
Green Gold High proportion of silver or cadmium
Blue Gold Some iron
Grey Gold 15-20% iron