Alteration characteristics of illmenites from south India

Abstract

Two different placer samples from the Navaladi and Surungudi area of Teri, Tamilnadu. in southern India. were collected and characterized in terms of their heavy mineral content. Mineralogical analysis on both the samples revealed the presence of high amounts of garnet and ilmenite. The alteration characteristics of ilmenite from these deposits were investigated by optical and electron probe microanalysis. Optical microscopic studies revealed that the alteration of ilmenite was seen to proceed along grain boundaries and/or fractures resulting in an amorphous to crypto- or microcrystalline mass resembling leucoxene. The alteration is in the nascent stage. Mineral chemistry by electron probe micro-analysis revealed the enrichment of Ti02, MgO, A1203•Cr203. Si02, V205 and Na20 in the altered products and loss of iron oxide and manganese oxide from the ilmenite grains during weathering leading to the formation of leucoxene. Similarly EPMA studies on garnet indicated that it is of the almandine variety. This study reveals that the alteration of ilmenite by weathering leads to unstable phases, with complex elemental distribution patterns. The physico-chemical characteristics of the mineral and, in turn, the down-stream metallurgical processing are affected by such alteration processes.