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Chaoite
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.〔A. El Goresy, G. Donnay, ''A new allotriomorphic form of carbon from the Ries Crater,'' Science, 1969, 161, 363–364〕 From its electron diffraction pattern, the mineral has been considered to have a carbyne structure,〔A.G. Whittaker, P.L. Kintner, Science 1969, 165, 589〕 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.〔P.P.K. Smith, P.R. Buseck, ''Carbyne forms of carbon: do they exist?'' Science, 1982, 216, 984–986〕
==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''.〔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〕
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".〔D.W. McKee, Annu. Rev. Mater. Sci. 1973, 3, 195〕
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