Transformation of graphite to diamond via a topotactic mechanism

Laurence Garvie, Péter Németh, P R Buseck

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Several mechanisms and intermediate steps have been proposed to explain the transformation of graphite to diamond. However, the mechanism continues to be debated, in part because graphite that is incompletely transformed to diamond has not been reported; although such material could be used to better understand the diamond-forming process. Here we report the discovery of nano-sized grains of interstratified graphite and diamond from Gujba, an extraterrestrially shocked meteorite. We use high-resolution transmission electron microscopy (HRTEM) data from these grains to show that diamond formed via a reconstructive, topotactic rather than martensitic mechanism. Electron diffraction and HRTEM images show the following three-dimensional crystallographic relationships between the interstratified graphite and diamond: (001)g||(111) d, (100)g||(211)d, and (120) g||(011)d. These relationships yield the transition matrix linking the graphite and diamond unit cells, which become coincident for graphite compressed to 7 GPa. The specific product, whether single-crystal or twinned diamond, is dictated by the initial graphite polytype and transformation route. The derivation of a three-dimensional transition matrix is consistent with a topotactic relationship between graphite and the newly formed diamond.

Original languageEnglish (US)
Pages (from-to)531-538
Number of pages8
JournalAmerican Mineralogist
Issue number2-3
StatePublished - Feb 2014


  • Crystal structure
  • crystal growth
  • electron microscopy
  • meteorite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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