LIQUID MAGNETIC SEPARATION OF IRON-BEARING MINERALS FROM SAND FRACTIONS OF SOILS

Abstract

The study provides a new liquid magnetic separation (LMS) technique for concentrating sand-sized iron-bearing minerals, in general, and for quantitative isolation of biotite, in particular, from soils. Sand fractions (100–250 μm), separated from untreated soil samples from a Gray Luvisol from Saskatchewan by ultrasonic dispersion and sieving, were processed by LMS at various levels of magnetic flux density. The LMS separates obtained at increasing level of magnetic flux density showed a decreasing iron content. A linear relationship was observed between the two variables within the range of 2.5–28.0% Fe2O3 and 0.15–0.92 Tesla (T) magnetic flux density with a correlation value of R = 0.99. Mineral grains with as low as 1.09% Fe2O3 content could be isolated from sand fractions at 1.31–1.45 T. The XRD analyses of LMS separates obtained at 0.305–0.58 T showed only biotite and its weathered products. The XRD analyses of other LMS separates showed a concentration of different solid solution series of the amphiboles, pyroxenes, garnets, tourmaline and other iron-bearing minerals in different fractions. The LMS technique is physical in nature and provides a simple, quick and effective means of isolating iron-bearing minerals from sand fractions of soils. Key words: Liquid magnetic separation, iron bearing minerals, biotite separation, sand mineralogy