Host: Japan Association of Mineralogical Sciences
The surface of a platy carbon grain is observed by SEM. In some areas, individual diamond crystals show triangular faces parallel to the surface of the grain surrounded by triangular pits. The Raman spectrum obtained at a triangular pit shows very broad Raman band at 1580 cm-1 which does not associated with D-band at 1350 cm-1. Like this characteristic pattern is observed distinctively for tetrahedral amorphous carbon (ta-C). The presence of ta-C in the pit suggests that the triangular pit has been formed by melting of carbon followed by quenching at a high pressure.
