Electrostatic Shape Separation of Flake Mica From Pegmatites

Electrostatic shape separation was considered to be an adequate technique for processing a particulate mixture of flake mica and isometric granules of feldspar and quartz. The authors carried out extensive laboratory experiments to concentrate flake muscovite from a pegmatitic product with content of 50 to 65% of mica. Prior to electroseparation, the granular material was dried and vibrating screens were employed to obtain two fractions: +1 mm (which represented more than 70% of the feed), and –1 + 0.315 mm. Each fraction was then treated in the corona–field roll–type separator. In the first group of experiments, two corona electrodes of opposite polarities were conveniently located relative to the grounded metallic roll carrier. The second group of experiments necessitated one corona electrode only, but the roll carrier was covered by a dielectric layer. These two electrostatic shape separation methods were discussed, based on a crude evaluation of the charges and forces which act on various constituents of the granular mixture. Mica concentrates with 45.47% SiO 2 , 36.08% Al 2 O 3 and 10.4% (K 2 O + Na 2 O) were obtained, using a two–stage electroseparation scheme. These products fulfill the requirements regarding the composition and the size distribution of the flake mica for several applications in the industry of electrical insulating materials.