Distribution and Textural Characteristics of the Heavy Minerals in the Beach and Dune Sands of Cox's Bazar, Bangladesh

The beach and coastal dune sands of Cox's Bazar constitute the most important source of metallic minerals in Bangladesh. The sands are fine, well-sorted, negatively skewed and leptokurtic in their grain-size distributions. Plots of different size parameters suggest that (a) the finer the grain-size the better is the sorting; (b) the sediments are more negatively skewed as the grain-size decreases; and (c) sorting improves as the skewness changes from nearly symmetrical to negative. The dune sands are finer, better sorted and more negatively skewed than beach sands. The percentage of heavy minerals increases from 2 φ (250 μ m) to 3.5 φ (88 μ m) fraction. The light fraction consists predominantly of quartz (about 90 %), while amphibole, ilmenite, garnet, epidote, mica, pyroxene, magnetite. kyanite, tourmaline, staurolite, zircon, rutile and monazite constitute the heavy minerals. The distribution of the heavies in the dunes and beaches depend on their respective shape. The equant ones are predominant in the former than in the latter. The predominance of unstable minerals and their shapes suggest that the major source of the sediment may be in the easterly highlands of Chittagong-Arakan hills.