A dry milling process for the production of ground mica

CIM Bulletin, Vol. 75, No. 842, 1982

JACQUES TURGEON, Ingenieur, et GONTRAN FOY, Directeur de I'Usine-Pilote, Centre de Recherches minerales, Ministere de I'Energie et des Ressources, Quebec

The Mineral Research Centre of the Quebec Department of Energy and Resources has worked extensively on the development of a dry process to extract pure mica flakes from a phlogopite ore. The liberation of mica from the gangue is effected basically by impact crushing, and the ground ore is screened into several fractions, each having a fairly narrow range of grain size. Each sized fraction is then fed to an air separator where heavy grains are separated from light flaky grains. Heavy fractions are returned to hammer mills where gangue minerals are ground finer and blacky mica particles are exfoliated. A second stage of screening is performed and each fraction is sent to an air separator. This sequence is repeated until mica products are virtually free of gangue. These different fractions are then treated in a cage mill in which mica flakes undergo a more orderly exfoliation along cleavage planes. The ground mica is again submitted to a final screening stage, after which each fraction constitutes a final commercial product.This process permits the recovery of about 70% of the mica contained in the ore. The over-all process will be described along with technical details of each unit operation. Recent work on a wet grinding method to produce very fine mica will also be discussed.
Mots Clés: Industrial minerals, Mica, Milling, Dry milling, Quebec, Suzor deposit, Suzorite, Crushing, Screening, Separation, Delamination. Grinding.