Gold

Gold is a chemical element in the periodic table with the symbol Au (from the Latin aurum) and atomic number 79. It is a highly prized precious metal that for millennia has been used as money, a store of value and in jewelry. The metal occurs as nuggets or grains in rocks and in alluvial deposits and is one of the coinage metals. It is a soft, shiny, yellow, dense, malleable, and ductile (trivalent and univalent) transition metal. Modern industrial uses include dentistry and electronics. Gold forms the basis for a common Earth monetary standard.

Gold is also notable as a major weakness of Cybermen. Due to its non-corrodable nature, gold essentially chokes their respiratory systems. For example, the glittergun, a weapon used during the Cyber-Wars in the future, fired gold dust at its targets. However, in later serials, gold appeared to affect them rather like silver affects werewolves, with gold coins or gold-tipped bullets fired at them having the same effect. Other weaknesses include solvents and excessive levels of radiation.

By the late 29th century, the Cybermen had been reduced to small remnant groups wandering around the galaxy. One group tried to take revenge by making a desperate attempt to blow up the remnants of the planet Voga, a planetoid of pure gold that had wandered into the solar system and become a moon of Jupiter. They hoped that this would disrupt their enemy's supply of the metal, but were stopped by the Fourth Doctor. (Revenge of the Cybermen)