Beneficiation of Low Grade Kyanite from Sirboi Mines of Singhbhum District

Kyanite is used mostly in the manufacture of high alumina, high performance refractories. The major workable deposits of kyanite occur in Singhbhum District of Bihar. Kyanite from Sirboi mines is however of low grade and need to be beneficiated to achieve the desired specification. The
sample assayed 40.43% At203 and 50.39% SiO, contained kyanite as mineral of economic interest with quartz constituted the bulk of gangue mineral.The liberation of kyanite from associated gangue was reported to be
below -48 mesh size. Gravity concentration by tabling at -48 mesh size were not very encouraging. Froth flotation studies using sodium silicate as depressant and oleic emulsion as collectorat alkaline circuit (pH 9.1 - 9.3)
did not respond to the desired grade or recovery. Flotation at pH (3.5)employing lactic acid as a depressant and sodium petroleum sulphonate as collector produced a concentrate assaying 60.3%a A1203, 33.8% SiO 2 and
0.38% Fe with 55.0% A1,O, recovery. Thus, the flotation concentrate produced in acid circuit (pH 3.5) meets the specifications and is suitable for blending with massive kyanite which is suitable for the manufacture of monolithic refractories.