Composition and texture of terrigenous-phosphate grains from the productive bed of the Unecha placer

Results of the study of the composition of rocks from the Unecha placer deposit and the morphology of phosphate segregations investigated by electron microscopy are presented. Several forms of the phosphate material occurrence, including the most abundant shells around grains of different configurations have been revealed. The studies carried out suggest a biogenic (bacterial-algal) nature of the phosphate material complicated by chemical metasomatism.[PUBLICATION ABSTRACT]