Beneficiation of a Gypsum sample from Rajasthan

A sample of gypsum from Rajasthan as received from M/S Mecanico, new Delhi assayed 37.83% SO3,SiO2, 1.49% Al2O3, 0.78%Fe2O3, 1.24% MgO and less than 0.01% NaCl. The gypsum content in the sample was 81.28%. The gangue minerals were mostly of concentration were required to be investigated in view of the scarcity of water near the gypsum deposits. Screening out the -100 mesh fraction after crushing the sample to -8 mesh fraction assaying 41.83 % SO3 (89.93% gypsum) with a recovery of 82.9% . Treatment of -100+200 mesh fraction in an electrostatic separator produced a concentrate assaying 37.35% SO3, which when mixed with the -8+100 mesh fraction assayed 41.44% SO3 (89.10% gypsum) with an overall recovery of 89.9%. Screening out the -200 mesh fraction instead of -100 mesh would produce a concentrate assaying 40.33% SO3 (86.7% gypsum) with a recovery of 92.6% of gypsum.