Chaoite, or white carbon, is a mineral described as an allotrope of carbon whose existence is disputed. It was discovered in shock-fused graphite gneiss from the Ries crater in Bavaria. It has been described as slightly harder than graphite, with a reflection colour of grey to white.[5] From its electron diffraction pattern, the mineral has been considered to have a carbyne structure,[6] the linear acetylenic carbon allotrope of carbon. A later report has called this identification, and the very existence of carbyne phases, into question, arguing that the new reflections in the diffraction pattern are due to clay impurities.[7]
Synthetic material
It has been claimed that an identical form can be prepared from graphite by sublimation at 2700-3000 K or by irradiating it with a laser in high vacuum. This substance has been termed ceraphite.[8]
A review cautions that "in spite of these seemingly definitive reports … several other groups have tried unsuccessfully to reproduce these experiments. Independent confirmatory work is obviously needed … and at the present time white graphite appears to be the carbon analog of polywater".[9]
Frans J. M. Rietmeijer and Alessandra Rotundi, Chapter 16. Natural Carbynes, Including Chaoite, on Earth, in Meteorites, Comets, Circumstellar and Interstellar Dust, in Polyynes: Synthesis, Properties, and Applications, Edited by Franco Cataldo, CRC Press 2005, Pages 339–370, Print ISBN978-1-57444-512-1 eBook ISBN978-1-4200-2758-7Contents link