Journal of Materials Science

, Volume 22, Issue 6, pp 1913–1918 | Cite as

Cellular intergrowth between quartz and sodium-rich plagioclase (myrmekite) — an analogue of discontinuous precipitation in metal alloys

  • R. Wirth
  • G. Voll


Gneissic rocks of the contact aureole of the Traversella Intrusion (N. Italy) reveal a cellular intergrowth of quartz and oligoclase (myrmekite), originating from alkali feldspar grain boundaries. The myrmekite occurs in a temperature range of 500 to 670°C. The size of the cells and the lamellar spacing of the quartz rods increase with rising temperature. A comparison of the characteristic features of myrmekite cells with discontinuous precipitation cells of alloys indicates many similarities between the reactions. A is concluded that the formation of myrmekite is a solid-state reaction; a supersaturated alkali feldspar decomposes into a cellular structure growing behind a moving incoherent grain boundary. Micro probe analyses of the original alkali feldspar, the reaction products, and the volume relationship of the reactants (quartz, sodium-rich plagioclase) show that an ion exchange occurs during the reaction (K+ removed; Na+, Ca2+ and Si4+ added). A model describing the early stages of the formation of myrmekite is presented.


Polymer Precipitation Quartz Characteristic Feature Cellular Structure 
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Copyright information

© Chapman and Hall Ltd. 1987

Authors and Affiliations

  • R. Wirth
    • 1
  • G. Voll
    • 2
  1. 1.Institut für Werkstofftechnologie Fachbereich 12.1 Bau 2Universität SaarbrückenSaarbrückenFRG
  2. 2.Mineralogisches Institut der Universität zu KölnKöln 1FRG

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