Raman spectroscopic and microscopic criteria for the distinction of microdiamonds in ultrahigh-pressure metamorphic rocks from diamonds in sample preparation materials

Natural diamond from three ultrahigh-pressure metamorphic (UHPM) terranes (Erzgebirge Massif, Germany; Kokchetav Massif, Northern Kazakhstan; Rhodope Metamorphic Province, Greece) and synthetic diamond from cutting and polishing materials (paste, spray, saw blade) were studied by means of optical microscopy and Raman microspectroscopy, to constitute a new petrographic and spectroscopic data set that might be a useful tool for identifying and characterizing metamorphic diamond. Several criteria are established for distinguishing natural microdiamond identified in a rock thin section from the externally introduced ones [i.e., diamond as residual particles (contaminants) from the cutting and polishing material] such as the diamond size, the presence of inclusions, coatings, or coexistent phases and two diamond Raman band parameters, i.e., the Raman shift and the full-width at half maximum height (FWHM).