A soft, yellow, metallic element, one of the transition metals . It is very unreactive, though attacked by halogens and aqua regia . Panning for gold in rivers has been superseded by hydraulic mining and deep mining .
Gold is extracted from the deposit by treatment with cyanide and displacement with zinc.
It is further purified by electrolysis or treatment with nitric and sulphuric acids. Its rarity, appearance, and lack of reactivity have led to gold being highly valued throughout history. Its value is thought to be more stable than that of many currencies, and it is widely held as an investment. A good conductor of heat and electricity, it is used widely in electronics. Pure gold is too soft for most applications and is generally hardened by alloying it with copper or silver.