Nano and sub-micro inclusions as probes into the origin and history of natural diamonds

Abstract

Five natural faceted diamond samples, considered to have inherent submicroscopic and nanometric inclusions, were studied using various techniques such as Raman spectroscopy, Raman microscopy, scanning electron microscopy (SEM), and energy dispersive analysis of X-rays (EDAX). The principal focus was to find out the chemical nature of the inclusions and their distribution. As a confirmative tool, laser desorption ionization mass spectrometry (LDI MS) was used for the characterization of the inclusions. Our study suggests that the inclusions in diamond belong to the pyroxene group of silicate minerals with Fe, Mg, Ca, Ru, and Cr as the major elements. As evidenced by the absence of alkali, aluminum, and rare earth elements in the inclusion, the diamond can be of peridotitic origin. Interestingly, we found that chromium scavenges Ru, a platinum group element (PGE), and other metals such as Nb, Co, and Ni, entrained into the pyroxene inclusions. We established that the diamond sample in which inclusions are found is of Kimberlitic origin.