Magnetic concentration of asbestos ore

CIM Bulletin, Vol. 72, No. 805, 1979

EDWARD MARTINEZ, Superintendent, Mineral Science, Central Research Department, ASARCO Incorporated, South Plainfield, N.J.

Laboratory studies had shown that the magnetite contained in serpentine asbestos ore was not uniformly distributed. Ore particles containing chrysotile fiber responded to a magnetic field; particles containing little or no chrysotile were essentially non-magnetic. Larger-scale tests, run with a magnetic pulley being fed various asbestos samples ranging in size from 1/4 inch to 5 inches, confirmed that magnetic separation could be used as a concentration step in an asbestos mill.Magnetic concentration was installed at the Black Lake and National mills of Lac d'Amiante du Quebec and has allowed the extraction of lower-grade ore, increasing the life of the mines. In addition, preconcentration early in the flowsheet increased the value of the feed to the fiber recovery section. An increase in fiber production was achieved, as well as a decrease in maintenance costs due to removal of low-grade tailings early in the flowsheet. Magnetic concentration of a coarse tailings from the mill resulted in recovery of additional fiber previously discarded to tailings.
Keywords: Asbestos ore, Industrial minerals, Concentration, Magnetic concentration, Chrysotile, Black Lake mill, National mill, Lake Asbestos of Quebec, Tailings recovery.