MAGNESITE-BEARING INCLUSION ASSEMBLAGE IN NATURAL DIAMOND

Abstract

A significant mineral assemblage has been found as an inclusion in a natural diamond from the Finsch kimberlite pipe of South Africa: a euhedral rhombohedron-shaped magnesite (MgCO3) crystal (d ∼ 30 μm) co-exists with several idiomorphic olivine [(Mg1.86Fe0.14)SiO4] grains (d ∼ 80 μm). Many tiny anatase (TiO2) particles (d ∼ 2–5 μm) and microcrystallites (d < 1 μm) of diamond and disordered graphite are attached to the surface of the magnesite grain. Structural and compositional characterization of the inclusion phases was achieved by micro-Raman spectroscopy and electron microprobe analysis.