Gold is a yellow precious metal, used in jewellery and decoration and to guarantee the value of currencies. This metal has been a valuable and highly sought after precious metal for coinage, jewellery, and other arts since long before the beginning of recorded history. A total of 174,100 tonnes of gold have been mined in human history. The world consumption of new gold produced is about 50% in jewellery, 40% in investments, and 10% in industry. Besides its widespread monetary and symbolic functions, gold has many practical uses in dentistry, electronics, and other fields. Its high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to many uses, including electric wiring, colored-glass production, and gold leafing. Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewellery, altering its hardness and ductility, melting point, color and other properties. Alloys with lower carat rating, typically 22k, 18k, 14k or 10k, contain higher percentages of copper or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color.