Beneficiation of a low-grade Graphite schist sample from Khepchishi Hill, Bhutan

Beneficiation studies were undertaken on a low-grade graphite sample from Khepchishi hill of Bhutan, received from the Director, Geological Survey of India, Bhutan Circle, Jalpaiguri Dt., West Bengal, with a view to producing a concentrate suitable for use in industry. The sample as received assayed 10.66% fixed carbon, 86.4% Ash, 2.94% volatile matter, 0.66% moisture, 0.18% Sulphur, 1.7% Fe in ash, 0.027% P2O2, and 1.1% TiO2.The principal gangue in the sample was quartz followed by micas and minor amounts of sillimanite, andalusite, rutile, apatite, goethite, limonite, and traces of feldspar, calcite, chlorite, and opaque. Graphite appeared disseminated in the gangue even at sizes finer than 200 mesh. Rougher flotation employing a feed of even -56 microns using pine oil as collector-frother followed by three cleanings of the rougher 63.4% Ec and 2.5% volatile matter, with a recovery of about 78% C. The concentrate although very fine, could perhaps be used for foundry facings and paint manufacture.