A new natural,super-hard,transparent polymorph of carbon from the Popigai impact crater,Russia |
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| Authors: | Ahmed El Goresy Leonid S Dubrovinsky Philippe Gillet Smail Mostefaoui Günther Graup Michael Drakopoulos Alexandre S Simionovici Varghese Swamy Victor L Masaitis |
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| Institution: | 1. Max Planck-Institut für Chemie, J. Joachim-Becher-Weg 27, 55128 Mainz, Germany;2. Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany;3. Laboratoire des sciences de la Terre, École normale supérieure de Lyon, 69364 Lyon, France;4. European Synchrotron Radiation Facility, 38043 Grenoble, France;5. CRCT, École polytechnique de Montréal, CP 6079, Montréal (Québec), H4C 3A7, Canada;6. Karpinsky Geological Institute, St. Petersburg, 199106 Russia |
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| Abstract: | A natural shockwave event led to the formation of a new crystalline polymorph of carbon in gneisses from the Popigai crater, Russia. The new species occupies the interior of a multiphase assemblage and is entirely enveloped by lonsdaleite and graphite. Polishing hardness of this new phase is greater than that of lonsdaleite. Micro-beam synchrotron X-ray diffraction, imaging and fluorescence studies revealed a pure transparent carbon phase. The diffraction pattern is indexed in terms of a cubic cell (a=14.697 Å, space group Pm3m.). This species was neither encountered in static or dynamic high-pressure experiment nor predicted by theoretical calculations. To cite this article: A. El Goresy et al., C. R. Geoscience 335 (2003). |
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| Keywords: | natural super hard carbon polymorph lonsdaleite Popigai shock-induced phase transition polymorphe naturel du carbone ultra-dur lonsdaléite Popigai transition de phase par choc |
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