Gold had a great and frequently mystic influence on people from the beginning of mankind, being used for jewellery, treasure, raw material, as a measure for money (universal currency) and has also been associated with divinity and royalty, promoting the yellow colour as a noble one in many civilizations. Additionally, it is also a symbol of the winners (gold medalists) and persistence (most wedding rings are made of gold). More recent medical and high-tech uses complete the importance of the metal in everyday life.
Pure gold is too soft for most manufacturing purposes. This is why it is used in alloys with other metals, which can alter its colour, generating varieties of white gold (allied with nickel, silver or palladium), red or pink gold (with copper) or blue gold (allied with iron). On the purpose of briefly stating of gold content in an alloy, the karat/carat system is used. Pure gold has 24 karat while an alloy with 50% Au has 12 karat, one with 75% Au has 18 karat etc.