Lonsdaleite, a rare hexagonal form of diamond found in ureilite meteorites, formed shortly after an inner solar system dwarf planet collided with a large asteroid about 4.5 billion years ago. Images of graphite, lonsdaleite, and diamond in ureilite meteorites: (A) reflected light image showing folded crystalline graphite, with fold morphology defined by graphite cleavage; different shading in the graphite is produced by axial planar kink bands; (B)...