The compression pathway of quartz

Richard M. Thompson, Robertrt T. Downs, Przemyslaw Dera

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The structure of quartz over the temperature domain (298 K, 1078 K) and pressure domain (0 GPa, 20.25 GPa) is compared to the following three hypothetical quartz crystals: (1) Ideal a-quartz with perfectly regular tetrahedra and the same volume and Si-O-Si angle as its observed equivalent (ideal ß-quartz has Si-O-Si angle fixed at 155.6°). (2) Model a-quartz with the same Si-O-Si angle and cell parameters as its observed equivalent, derived from ideal by altering the axial ratio. (3) BCC quartz with a perfectly body-centered cubic arrangement of oxygen anions and the same volume as its observed equivalent. Comparison of experimental data recorded in the literature for quartz with these hypothetical crys-tal structures shows that quartz becomes more ideal as temperature increases, more BCC as pressure increases, and that model quartz is a very good representation of observed quartz under all conditions. This is consistent with the hypothesis that quartz compresses through Si-O-Si angle-bending, which is resisted by anion-anion repulsion resulting in increasing distortion of the c/a axial ratio from ideal as temperature decreases and/or pressure increases.

Original languageEnglish (US)
Pages (from-to)1495-1502
Number of pages8
JournalAmerican Mineralogist
Issue number10
StatePublished - Oct 2011


  • BCC quartz
  • Brazil law twins
  • Crystal structure
  • Dauphiné twin
  • High-pressure studies
  • High-temperature studies
  • Ideal quartz
  • Model quartz

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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