Gold is a dense, soft, shiny metal and the most malleable and ductile metal known. Pure gold has a bright yellow colour and luster traditionally considered attractive, which it maintains without oxidizing in air or water. 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, colour and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy.