Native gold crystals. This soft, heavy, acid- resistant metal is usually found in quartz veins, as a natural alloy with silver, and in concentrations of sedimentary origin. The main gold-bearing districts are Witwatersrand (South Africa), the Mother Lode (California, USA), the Yukon (Alaska, USA), Porcupine (Northwest Territory, Canada) and the USSR. It is used as a monetary standard, in jewellery, in dentistry and for scientific and electronic instruments.