HPHT-Treated Impact Diamonds from the Popigai Crater (Siberian Craton): XRD and Raman Spectroscopy Evidence

Phase change and graphitization of diamonds from the Popigai impact crater (Krasnoyarsk Territory, Siberian platform, Russia) exposed to high-pressure high-temperature (HPHT) conditions 5.5 GPa 2000–2200 °C are studied by Raman spectroscopy X-ray diffractometry (XRD). Light-color type 1, free inclusions, with 0 10 % lonsdaleite, more resistant HPHT effects than dark 2 rich in lonsdaleite graphite. The lonsdaleite/diamond ratios lonsdaleite-bearing become smaller upon annealing, possibly because transforms cubic diamond simultaneously graphitization. Therefore, is likely a structure defect separate hexagonal phase.