Gold (symbol: Au atomic number :79) is found in nature as the free metal and in tellurides. About two thirds of the world's gold output comes from South Africa. The metal is recovered from its ores by amalgamating, cyaniding, and smelting processes. Refining is also done by electrolysis. Of all the elements, gold in its pure state is undoubtedly the most beautiful. It is metallic, having a yellow color when in a mass, but when finely divided it may be black, ruby, or purple. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents. It is used in coinage and is a standard for monetary systems in many countries. It is also extensively used for jewelry, plating, and for dental work. A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia. Gold is available commercially with a purity of nearly 100%.
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