Mining operations began at Kunwarara in 1991.The Kunwarara - Yaamba magnesite deposits extend from between 40 kilometres and 70km north of Rockhampton in Central Queensland.
The main deposit forms an irregular channel more than 30km long, and varying in width from 500 metres up to 3km. The magnesite deposit is formed within river gravels and sands of a former north-flowing meandering river system. Magnesite has been deposited from magnesium-rich ground waters derived from the weathering of adjacent serpentinite basement rocks, and has grown to form accretionary nodules.
About three million tonnes of ore is mined annually and processed through the beneficiation plants at the site’s KG1 and KG2 areas.
From 1991 to 1999 mining was focused on the KG1 area, which is also the location of the beneficiation plant. Mining began at KG3 in 1999 and at KG2 in 2000, and development of the adjoining Oldman South lease was scheduled to begin in 2007.
A second pre-concentration plant comprising crushing, scrubbing and screening circuits was constructed at KG2 in 2000.
Beneficiated low calcium/low silica magnesite feedstock is trucked to the processing plant at Parkhurst.
Pits are developed sequentially to balance product quality requirements and generally contain about 300Mt to 500,000Mt of run-of-mine ore. After stripping of overburden, the magnesite is mined on 3m benches.
To the end of 2006, Queensland Magnesia had mined about 43Mt of ore and produced in excess of 5.7Mt of high-grade beneficiated magnesite.
Kunwarara produced 174,467t of magnesia to December 31, 2004. To June 30, 2002 the mine had proven probable reserves of 114.9Mt.