Exploring for graphite: opportunities and challenges

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SRK News | Issue 57Exploration Geology: Keys to success

Mike Cunningham, Geologist


Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. Its unique physical and chemical properties make it well-suited to many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. Global demand for natural graphite doubled between 2006 and 2012. Although Chinese industrial activity has slowed and led to prices falling from the high levels seen in 2011, consumption of smart electronic devices has caused a growth in demand and this may continue to grow as sales of electric and hybrid vehicles require larger batteries. China and India are the largest graphite producers, with over 80% of global production. Chinese graphite, however, is declining in quality while production costs are increasing. China has a 20% export duty on graphite, a 17% value added tax, and has instituted an export licensing system to ensure supply to its domestic economy, creating supply concerns for the rest of the world.

Graphite generally forms from high-grade metamorphism of organic matter in sediments. The three main types of commercially significant natural graphite are crystalline or disseminated flake, crystalline vein or lump, and microcrystalline or amorphous graphite. The largest flake graphite deposits are often relatively low grade. In contrast, vein graphite deposits are smaller and higher grade. Amorphous deposits can range in size but generally produce lower quality graphite with restricted uses. Recent exploration has focused on flake graphite in East Africa, Canada and Australia. The largest deposits are in Mozambique and Tanzania, an area noted for large, high purity flake graphite. This increased exploration activity has resulted in global inferred resources exceeding 800 Mt (USGS, 2015).

The value of graphite deposits depends on grade, purity, size and range of flakes or needles, and the presence of impurities that may have a negative effect on extraction. Pricing is complex and depends on total graphitic carbon (TGC) content; deposits with grades of over 80% TGC are economically viable.

The two main assay methods for measuring TGC are: LECO analysis and Double Loss of Ignition (DLOI). DLOI is normally used as a graphitic indicator, while the LECO method provides a more detailed assessment. DLOI may not always accurately represent the actual TGC values in the rock as the measurements can be affected by the presence of sulphides and calcite (carbonate). Processing flake graphite aims to optimise the liberation of flakes by size (Large: +180μm; Jumbo: +300μm; and Super Jumbo: +500μm flakes) and to maximise grade and recovery. Evaluating the economic potential of graphite samples requires an understanding of the extraction process. Over 80% of graphite demand is still driven by industrial applications. Predictions see the battery sector increasing market share over the next few years with a rebound in the steel industry having potential to also fuel demand.

Mike Cunningham: mcunningham@srk.com.au

 

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