TEM observation of diamonds in ureilites: Transformation mechanism from graphite

Abstract

Diamond in ureilites was first reported in 1888. The genesis of diamond in meteorites has been a problem of many years. The existence of compressed graphite associated with diamond reveals that diamonds in ureilites formed as a result of shock conversion of graphite. Mechanism of conversion from graphite to diamond has also been discussed based on high-pressure experiments and molecular dynamics. However, direct observation of diamond in ureilites suggesting conversion mechanism has not been done until now. In this study, we observed diamonds associated with graphite by a high resolution transmission electron microscopy (HRTEM).