Contributions to Mineralogy and Petrology

, Volume 74, Issue 2, pp 135–141 | Cite as

The distortion index in anhydrous Mg-Cordierite

  • A. Putnis


The mechanism of the hexagonal-orthorhombic transition in anhydrous Mg-cordierite has been studied by isothermal annealing experiments on synthetic samples. Products have been characterized by X-ray powder diffractometry and transmission electron microscopy. The transformation is first order and at temperatures below about 1,450° C the stable phase is orthorhombic cordierite with a distortion index,Δ≈0.25. Under non-equilibrium conditions the transformation takes place via a modulated structure which on annealing, coarsens to produce an apparently continuous sequence of metastable intermediateΔ values. The limitations of the distortion index as an indicator of the structural state of anhydrous Mg-cordierite are discussed in terms of short-range and long-range distortions associated with the transition.


Microscopy Electron Microscopy Transmission Electron Microscopy Mineral Resource Structural State 
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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • A. Putnis
    • 1
  1. 1.Mineral Sciences Group, Department of Earth SciencesUniversity of CambridgeCambridgeEngland

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