Graphite, the hexagonal crystalline form of carbon, occurs naturally as disseminated crystal flakes in high-grade metamorphic rocks, as veins, and as microcrystalline ‘amorphous’ graphite associated with metamorphosed coal seams. The major market for graphite is in the production of heat resistant ‘refractory’ linings where it is added as an important minor component to magnesia or alumina refractories used for lining furnaces and continuous casting equipment for steel production. Other markets include coating foundry moulds, brake linings, batteries, carbon brushes and lubricants.
World demand for graphite increased steadily throughout 2012 and 2013. China produced the majority of the world's graphite, with in descending order of tonnage, China, Mexico, Canada, Brazil and Madagascar accounting for 97% of the tonnage. Australia's only operating graphite mine (commissioned in mid 2014) is the Uley Graphite Mine, 23 km form Port Lincoln, and owned and operated by Valence Industries.
South Australian Occurrences
Statewide there are >60 recorded graphite occurrences, with the most significant region being eastern Eyre Peninsula.
Eyre PeninsulaDisseminated flake graphite is widely distributed in metamorphosed Palaeoproterozoic Hutchison Group rocks. On eastern Eyre Peninsula, numerous occurrences have been recorded over a 200 km long zone extending from south of Port Lincoln to Kimba. The largest resources are in the southern portion of this zone, and comprise the Mikkira Graphite Province which contains resources of ~350 Mt at 6–7% graphite inferred from geophysical surveys and the drilling of five prospects. This is the largest reported graphite resource in Australia and includes the Uley Graphite Mine, 18 km west-southwest of Port Lincoln (Fig. 1).
Uley was discovered in the 1910s and has been worked intermittently since the late 1920s. Exploration during the 1980s led to reopening the mine in 1986 but a sharp decline in world graphite prices in 1992 saw the operation placed on care and maintenance in 1993. Indicated resources are 2.9 Mt grading 13% graphitic carbon, including 1.5 Mt at 15% graphite. Graphite formed by high-grade metamorphism of carbonaceous sediments of the lower Middleback Subgroup which, at the mine, are tightly folded along the hinge of a regional, north-plunging anticline (Fig. 2). Processing comprised separation of 0.1–2 mm graphite flakes from weathered schist and gneiss by processes of grinding in a rod mill, froth flotation and gravity separation using Wilfley tables. Product from the mine was sold as coarse (+300 µm) and medium flake (+150 µm) in grades 90–94% graphite.
Other significant resources on Eyre Peninsula have been identified. These include The Koppio and Kookaburra Gully deposits with the resource figure for Kookaburra Gully 2.25 Mtonne at 15% TGC (total graphite content), for 338,000 tonne contained graphite (using a 5% 5TGC cutoff). Also the Campoona Syncline region with the Wilclo South deposit at 6.38 Mtonne at 8.8% TGC, and Campoona Shaft deposit at 2.17 M tonne at 9.6% TCG. Several companies are actively exploring the eastern Eyre Peninsula, and prospects for significant increases in graphite resource are good.
High graphite contents have been reported in schist units during gold and base metal exploration in the Olary district. The graphite is typically fine grained and has not been assessed for commercial uses. Occurrences of minor graphite are known from Precambrian rocks of the Mount Lofty Ranges near Woodside, Williamstown and Truro.
Keeling, J.L., 2000. Uley graphite - a world class resource. MESA Journal, 18:6-11.
McNally, T.C., 1997. Uley graphite deposit. MESA Journal, 5:16-18.
Valentine, J.T., 1994. Graphite in South Australia — a review of production, use and geology. South Australia. Department of Mines and Energy. Report Book, 94/24.