BHP Billiton Limited discovers, acquires, develops, and markets natural resources worldwide. It operates through four segments: Petroleum, Copper, Iron Ore, and Coal. The company explores for copper, silver, lead, zinc, molybdenum, uranium, gold, and iron ores, as well as metallurgical coal, thermal energy coal, and oil and gas properties. It also engages in the mining, smelting, and refining of nickel; the provision of freight, finance, administrative, trading, marketing, and support services; and potash development activities. The company was formerly known as BHP Limited and changed its name to BHP Billiton Limited in July 2001. BHP Billiton Limited was founded in 1851 and is headquartered in Melbourne, Australia. BHP Billiton Limited is a subsidiary of BHP Billiton Group.