Magnesite

Content maintained by Roy Towner

• Magnesite
• Resources
• Accessible EDR
• JORC Reserves
• Exploration
• Production
• World Ranking
• Industry Developments

Magnesite (magnesium carbonate MgCO3) is marketed in three main forms:

• crude magnesite, primarily for use in chemicals and agriculture;
• dead-burned magnesia, a durable refractory used in the cement, glass, steel and metallurgical industries; and
• caustic calcined magnesia, for use in making oxychloride and oxysulphate cements for flooring and wallboards, mouldings and acoustic tiles as well as various environmental and chemical applications.

Economic Demonstrated Resources (EDR) of magnesite remained unchanged in 2010 at 330 million tonnes (Mt). South Australia (SA) remained Australia’s largest holding of EDR with 235Mt of magnesite, which is unchanged from 2006. The bulk of these resources occur as interbeds of sedimentary magnesite within the Skillogalee Dolomite at the Witchelina and Mount Hutton deposits, up to 30 kilometres (km) northwest of Leigh Creek. The average magnesite grade is 40% magnesium oxide (MgO).

Queensland (Qld) has Australia’s second largest inventory with 63Mt of magnesite EDR. The bulk of this resource occurs at Kunwarara 70km northwest of Rockhampton, where Queensland Magnesia Pty Ltd has global resources of 1200Mt of magnesite bearing material. Within this global resource, which has an Inferred Resource of 500Mt of magnesite, several high-grade magnesite zones have been classified as EDR. The Kunwarara deposit occurs as sheet-like lenses of magnesite with an average thickness of 7.6 metres (m) extending over an area of about 63 square kilometres. It contains four high-grade zones of very high-density bone-type, low iron ultrafine-grained cryptocrystalline to microcrystalline nodular magnesite.

The third largest inventory of EDR is in Tasmania (Tas) where the Arthur River deposit has a measured resource of 13.2Mt with an average magnesite grade of 43.4% MgO. The resource is part of a much larger global resource of 195Mt in the Arthur-Lyons River area, about 53km south of Burnie.

The remainder of Australia’s EDR occurs in the Winchester deposit 70km south of Darwin in the Northern Territory (NT), at Thuddungra 80km northwest of Young in New South Wales (NSW), and at Bandalup 20km east of Ravensthorpe in Western Australia (WA).

Subeconomic Demonstrated Resources of 57Mt of magnesite remained unchanged from 2006. All of these resources occur at Triple Four in central Qld and at Main Creek in northwest Tas.

Inferred Resources of magnesite increased slightly in 2010 to 836Mt (826Mt in 2009) with Qld accounting for 56% followed by SA with 35% and Tas with 5%. The remaining resources are in New South Wales, the Northern Territory and Western Australia.

All magnesite EDR is accessible for mining.

Joint Ore Reserves Committee (JORC) Code reserves comprise total magnesite in Proved and Probable Ore Reserves as defined in the JORC Code. In 2010, JORC Code reserves of 37.5Mt (unchanged from 2009) accounted for approximately 11% of Accessible Economic Demonstrated Resources (AEDR). At Australia’s 2009-10 rate of production, magnesite resources in the JORC Code reserves categories are adequate for almost 135 years.

Data associated with exploration expenditure for magnesite are not published by the Australian Bureau of Statistics.

The bulk of Australia’s magnesite production was by Queensland Magnesia Pty Ltd which supplied high-grade electrofused and dead-burned magnesia to the global refractory market, as well as calcined magnesia for a wide range of applications. In 2009-10, the company produced a total 275 819 tonnes of magnesite (344 962 tonnes in 2008-09). About 1618 tonnes of magnesite was produced from the Myrtle Springs region in SA in 2009.

According to Geoscience Australia and United States Geological Survey (USGS) data, Australia has about 4% of the world’s EDR of magnesite, which total 8400Mt. Russia, China and North Korea jointly accounting for almost 63% of the world’s EDR. The Kunwarara deposit in Qld is the world’s largest known resource of ultrafine-grained cryptocrystalline to microcrystalline nodular magnesite.

The USGS data indicated that world production of magnesite totalled 19.53Mt. The world’s largest producers of magnesite in 2010 were China (57%), Turkey (11%), North Korea (6%) and Russia (5%).

Korab Resources Limited has received a number of offers to establish a syndicate with the view to developing the Winchester magnesite deposit, initially as a supplier of magnesium oxide (MgO) based building products. MgO is used extensively in Canada, Asia and the USA to produce low-cost, high-strength building materials which do not expand or shrink when submerged in water or heated and are potential substitutes for fibro-board, plaster-board, chipboard and ceramic tiles. MgO based products are fire-resistant to 1200°C. The project has a JORC Code Indicated Resource of 12.2Mt grading 43.1% MgO and an inferred resource of 4.4Mt grading 43.6% MgO.

Beacon Hill Resources Plc plans to mine magnesite at the Arthur River deposit, which it acquired through the acquisition of Tasmania magnesite NL in 2009, in northwest Tas at a proposed production rate of 300 000 tonnes per annum. The company is undertaking a scoping study which it anticipates completing by early 2012.The study will include capital and operating cost estimates for a mine design, transport logistics and infrastructure, and the costs associated with the calcining the magnesite at several locations. The Arthur River Project has a defined JORC compliant Measured Resource of 13Mt of magnesite and an Inferred Resource of 10Mt.