Chaoite

Chaoite
General
CategoryNative element mineral
Formula
(repeating unit)		C
IMA symbolCh[1]
Strunz classification1.CB.05b
Crystal systemHexagonal
Crystal classDihexagonal dipyramidal (6/mmm)
H-M symbol: (6/m 2/m 2/m)
Space groupP6/mmm
Unit cella = 8.948 Å, c = 14.078 Å; Z = 168
Identification
ColourBlack
Crystal habitThin 3-15 μm intergrowth lamallae with graphite
Mohs scale hardness1 - 2
LustreSubmetallic
DiaphaneityOpaque
Specific gravity3.43 (calculated)
References[2][3][4]

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]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ 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