Abstract

Study of the heavy mineral assemblages of beach sands from Mozambique, Ceylon, Florida, and Brazil indicates that they consist largely of ilmenite in various stages of alteration. Three successive stages of alteration are recognized, and their optical and X-ray characteristics are described. The final product of alteration is commonly finely crystalline rutile, but leucoxene composed of finely divided brookite has also been identified.Alteration is accompanied by progressive decrease in magnetic susceptibility. The materials studied can be separated magnetically into fractions in which ilmenite grains showing various stages of alteration are concentrated differentially. The fractions therefore differ markedly in chemical composition.

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