Chaoite

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Chaoite
General
CategoryNative element mineral
Specific gravity
3.43 (calculated)
References[2][3][4]

Chaoite, or white carbon, is a

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]

Occurrence and discovery

Chaoite was first described from

Anabarskii massif of Eastern Siberia.[2][3] Minerals associated with chaoite include: graphite, zircon, rutile, pseudobrookite, magnetite, nickeliferous pyrrhotite and baddeleyite.[2]

See also

References

  1. S2CID 235729616
    .
  2. ^ a b c d Handbook of Mineralogy
  3. ^ a b c d Chaoite on Mindat.org
  4. ^ Chaoite on Webmineral
  5. ^ A. El Goresy, G. Donnay, A new allotriomorphic form of carbon from the Ries Crater, Science, 1969, 161, 363–364
  6. ^ A.G. Whittaker, P.L. Kintner, Carbon: observation on the new allotropic form, Science 1969, 165, 589
  7. ^ P.P.K. Smith, P.R. Buseck, Carbyne forms of carbon: do they exist? Science, 1982, 216, 984–986
  8. ^ C. Nakayama, M. Okawa, H. Nagashima, Carbon 1977, 15, 434; D.J. Johnson, D. Crawford, C. Oates, 1971, 10th Carbon Conf, Bethlehem, PA, FC-18
  9. ^ D.W. McKee, Annu. Rev. Mater. Sci. 1973, 3, 195

Further reading

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

ISBN 978-1-4200-2758-7 Contents link

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