PHOTOHONIOMETRY OF DIAMOND CRYSTALS DISSOLVED IN HETEROGENEOUS MEDIA UNDER 4 GPa PRESSURE AT 1400 °C
In result of experimental dissolution of diamonds at 4 GPa and 1400 °C in a heterogeneous solvent (Fe-S melt with addition of natural kimberlite in amount of 5 wt %), it has been revealed that, while the dissolution process, regardless of their initial shape, diamond crystals are transformed into octahedroids. The role of silicate additives appears in local screening of the diamonds surface with formation of etching hillocks, which gives to crystals the visually complex external morphology. Thus, morphologically complex natural diamonds with irregular shapes might be formed by dissolution with heterogeneous solvents in the mantle. Metal-sulfide-silicate melts consisting of immiscible components with different carbon solubility are the most likely candidates for such solvents.