Investigations on the Separation of Clay Minerals and Non-clayey matters of some Indian clays

Abstract

Six Indian clays were separated into several fractions according, to their particle sizes by gravity and centrifugal sedimentation methods and the chemical and mineralogical compositions of the fractions were studied by carrying out DTA, bee measurement, chemical and X-ray analysis and electrochemical measurements. Rajmahal clay contains only kaolinite in the fractions below 2 size whereas the fraction above 10μ size contains an appreciable amount of quartz. Tinpahari bentonite consists of montmorillonite in fractions below 5μ size. Iron and titanium rich minerals such as, haematite and rutile are concentrated in the fraction above 5μ size.In Cossimbazar clay feldspar is concentrated in the fraction above 10 μ size, whereas illite and kaolinite concentrated in fractions up to 0.5 μ size and montmorillonite in the fraction below 0.2μ size.Quartz is concentrated in fractions up to 2μ size of Rajhara fire clay, kaolinite in 2—0.2 μ size fraction and illite in the fraction below 0.075 μ size. This illite appears to differ from the normal one. Iron minerals are concentrated in two intermediate fractions, viz. 0.5–0.2 μ and 0.2–0.075μ size.Mineralogical (Compositions of Common clay and Chinsura soil are essentially the same and different minerals are concentrated in different fractions in the same way. Quartz is retained in fractions up to 2 μ size, illite and montmorillonite together with small amounts of kaolinite and quartz in fractions 2–0.2 size and illite and montmorillonite in the fraction below 0.2μ size. In Rajhara clay, Chinsura soil and Common clay, organic matter is detected in all the fractions.There is an indication of the presence of mixed layer minerals of illite and montmorillonite in the finest fraction of Common clay and Chinsura soil.