lonsdaleite
Rare,
hexagonal polymorph of
Diamond, believed to have formed when
meteoric Graphite makes an impact on earth. Prior and during the impact, great heat and stress transformed the Graphite into Diamond, though retaining Graphite's hexagonal
crystal lattice. Lonsdaleite is found only in a few
crater deposits such as the famous Barringer Crater in Arizona. Lonsdale is also know as "Hexagonal Diamond". As it differs in crystal structure, Lonsdaleite is scientifically categorized as an individual mineral species. It is named in honor Kathleen Lonsdale (1903-1971), a
crystallographer at the University of London.