Pristine presolar silicon carbide

We report the results of a study of 81 micrometer-sized presolar SiC grains in the size range 0.5–2.6 μm from the Murchison (CM2) carbonaceous chondrite. We describe a simple, nondestructive physical disaggregation technique used to isolate the grains while preserving them in their pristine state, as well as the scanning electron microscopy energy-dispersive X-ray mapping procedure used to locate them. Nine-tenths of the pristine SiCs are bounded by one or more planar surfaces consistent with cubic (3C polytype) crystal faces based on manifest symmetry elements. In addition, multiple polygonal depressions (generally