The crystal structure of preiswerkite

R. Oberti, L. Ungaretti, A. Tlili, D. C. Smith, J. L. Robert

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The structure of preiswerkite, ideally Na(Mg2Al)(Si2Al2)O10(OH)2, from the type locality at Geisspfad in Switzerland, has been determined by single-crystal X-ray diffraction and refinement. The polytype is 1M with space group C2/m. The unit-cell parameters are a = 5.228(7), b = 9.049(10), c = 9.819(12) Å, β = 100.42(13)°. Preiswerkite shares specific structures properties with a number of micas with very different compositions; apart from tetrahedral ordering, the closest structural analogue seems to be ephesite, ideally Na(LiAl2)(Si2Al2)O10(OH)2, which differs chemically only by the octahedral substitution Mg + Mg ⇌ Li + Al. -from Authors

Original languageEnglish
Pages (from-to)1290-1298
Number of pages9
JournalAmerican Mineralogist
Issue number11-12
StatePublished - 1993
Externally publishedYes


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