Geology of a Tantalite Pegmatite from Belangi, Surguja District, Madhya Pradesh, India

The tantalite pegmatite from Belangi is zoned and comprises a quartz core, blocky microcline perthite, intermediate zone, wall and border zones of contrasting composition. Tantalite occurs as blocks, and in massive, radiating and finely fragmented forms. It is randomly distributed in pockets, mostly close to quartz core. The pegmatite is potassic. Presence of successive zones of contrasting composition and absence of mineral replacements, with a high value of triclinicity (0.95) for microcline perthite indicate that the pegmatite was fonned by fractional crystallisation in a closed system. Columbite-tantalite from the pegmatite has very low Nb/Ta ratio (0.38 - 0.52). The pegmatite has yielded beryl and ruby variety of muscovite of marketable grade, besides tantalite.