This excerpt taken from the BHP 20-F filed Sep 14, 2009.
HMM owns the Mamatwan open-cut mine and the Wessels underground mine. The ore contained in these mines requires only crushing and screening to create saleable product with no further upgrade steps required. These assets produced 2.1 million tonnes of ore during FY2009 and have opportunities for further expansion. In FY2009, production was reduced in response to lower demand as a result of the global economic slow down. At FY2008 production rates, Mamatwan and Wessels have reserve lives of 22 and 49 years.
As a result of its location near our own port facilities and its simple, open-cut mining operation, GEMCO is one of the lowest-cost manganese ore producers in the world. Simple operations combined with its high-grade of ore and relative proximity to Asian export markets make GEMCO unique among the worlds manganese mines. GEMCO produced over 3.5 million tonnes of ore in FY2008. In FY2009, production was reduced to 2.3 million tonnes in response to lower demand. At a production rate of four million dry tonnes per annum, it has a reserve life of 14 years. The GEMCO expansion project was completed in FY2009 and we are studying other expansion options (see Development projects below).