An Ultradense Polymorph of Rutile with Seven-Coordinated Titanium from the Ries Crater

@article{Goresy2001AnUP,
  title={An Ultradense Polymorph of Rutile with Seven-Coordinated Titanium from the Ries Crater},
  author={Ahmed El Goresy and Ming Chen and Leonid S. Dubrovinsky and Philippe Gillet and Günther Graup},
  journal={Science},
  year={2001},
  volume={293},
  pages={1467 - 1470}
}
We report the discovery of an ultradense post-rutile polymorph of titanium dioxide in shocked gneisses of the Ries crater in Germany. The microscopic diagnostic feature is intense blue internal reflections in crossed polarizers in reflected light. X-ray diffraction studies revealed a monoclinic lattice, isostructural with the baddeleyite ZrO2 polymorph, and the titanium cation is coordinated with seven oxygen anions. The cell parameters are as follows: a = 4.606(2) angstroms, b = 4.986(3… 

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