X-Ray Study of Rare Phosphate Minerals

Abstract

A RARE phosphate mineral assemblage is found in an abandoned mica pegmatite in Sorhee mica mine, north of Laldaiya Pahar (24° 47′ N., 86° 10′ E.; Survey of India, Sheet 72 L/1), Monghyr, Bihar. The main pegmatite, worked over a zone of about 200 ft. with a width of nearly 130 ft., intrudes schistose rocks striking N. 25° W. with a dip of about 60° towards W.S.W. The rare phosphate minerals occur as an aggregate, forming bands sometimes more than 2 in. wide and 8 in. long, veined with quartz. The X-ray powder diffraction study shows that the phosphate assemblage consists of graftonite (pale pink) and triphylite (bluish green) with traces of heterosite (purple). A brown mineral, the powder pattern of which is identical with that of rhodonite (manganese silicate), and an unidentified black mineral with rhodochrosite, pyrolusite, hæmatite and amorphous admixtures are also associated in the assemblage.