Mining
Mining operations commenced at Kunwarara in 1991. From 1991 to 1999 mining was focused on KG1, which is also the location of the beneficiation plant. Mining commenced at KG3 in 1999 and at KG2 in 2000, and development of the adjoining Oldman South lease will commence in 2007.
A second pre-concentration plant comprising crushing, scrubbing and screening circuits was constructed at KG2 in 2000.
Approximately three million tonnes of ore is mined annually and processed through the beneficiation plants at KG1 and KG2. Beneficiated low calcium/low silica magnesite feedstock is trucked to the QMAG processing plant at Parkhurst.
To the end of 2006, QMAG has mined approximately 43 million tonnes of ore and produced in excess of 5.7 million tonnes of high-grade beneficiated magnesite.
Beneficiation plant reject material which comprises matrix sands, clays and gravels, and magnesite and dolomite fines, is pumped or trucked to mined-out pits and re-deposited as tailings. The tailings settle and compact fairly rapidly, allowing an ongoing process of top-soiling and rehabilitation.
Mining operations are relatively straightforward. Soil and clay overburden average 2-4m, and pits are typically only 15-18m deep. Pits are developed sequentially to balance product quality requirements and generally contain approximately 300-500,000mt of ROM ore. After stripping of overburden, the magnesite is mined on 3m benches. Areas planned for mining are drilled to provide detailed information on grade distribution to allow detailed planning and scheduling of mine production.