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An infrared spectroscopic study of hydrogen feldspar (HA1Si3O8) (1995)

Behrens, H. ; Müller, G.

Mineralogical Society of Great Britain and Ireland

In: Mineralogical Magazine. 1995; 59(394): 15-24. Published 1995 Mar 01. doi: 10.1180/minmag.1995.59.394.02.

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Publication Date: 1995-03-01

Description: Hydrogen in H-feldspar obtained by ion-exchange was studied in the spectral range 1000–5500 cm−1 by single crystal IR microspectroscopy. Spectra were almost identical for H-feldspars prepared either from sanidine or from adularia. Two bands in the middle-infrared were identified by D/H exchange as OH vibration modes. One broad band with a maximum at 3000 cm−1 and shoulders at 2800, 3200 and 3500 cm−1 confirms previous work. An additional OH absorption band with a maximum at 2485 cm−1 was observed for the first time in feldspars. The pleochroism of the OH absorption bands suggests that the H-feldspar is composed of two phases, an amorphous phase and a feldspathic phase. The proportion of the amorphous phase is increased by heating, producing a shift of the maximum of the band at 3000 cm−1 towards higher wavenumber and a decrease of the intensity of the band at 2485 cm−1. Near-infrared spectroscopy showed that hydrogen is present as hydroxyl groups bound to tetrahedral cations in both phases. Molecular water was not detected. The experimental results imply that hydrogen is incorporated in the H-feldspars as protons attached to bridging oxygen as well as to non-bridging oxygen. The complex structure of the IR spectra implies that the protons are distributed over a large number of sites in the cation cavity of the feldspars.

Print ISSN: 0026-461X

Electronic ISSN: 1471-8022

Topics: Geosciences

Published by Mineralogical Society of Great Britain and Ireland

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Nomenclature of the micas (1999)

Rieder, M. ; Cavazzini, G. ; D’yakonov, Yu. S. ; [et al.]

Mineralogical Society of Great Britain and Ireland

In: Mineralogical Magazine. 1999; 63(2): 267-279. Published 1999 Apr 01. doi: 10.1180/minmag.1999.063.2.13.

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Publication Date: 1999-04-01

Description: End-members and species defined with permissible ranges of composition are presented for the true micas, the brittle micas, and the interlayer-deficient micas. The determination of the crystallochemical formula for different available chemical data is outlined, and a system of modifiers and suffixes is given to allow the expression of unusual chemical substitutions or polytypic stacking arrangements. Tables of mica synonyms, varieties, ill-defined materials, and a list of names formerly or erroneously used for micas are presented. The Mica Subcommittee was appointed by the Commission on New Minerals and Mineral Names of the International Mineralogical Association. The definitions and recommendations presented were approved by the Commission.

Print ISSN: 0026-461X

Electronic ISSN: 1471-8022

Topics: Geosciences

Published by Mineralogical Society of Great Britain and Ireland

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