Triclinic liddicoatite and elbaite in growth sectors of tourmaline from Madagascar

M. Akizuri, T. Kuribayashi, T. Nagase, A. Kitakaze

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22 Citations (Scopus)

Abstract

Crystals of liddicoatite-elbaite tourmaline from a pegmatite in Jochy, Madagascar are composed of o{0221}, r{1011}, c{0001}, a{1120}, and m{1010} sectors, which correspond to the prominent crystal faces, respectively. Therefore, the sectors were produced during growth, not by strain after growth. The o, m, and r sectors of one specimen are biaxial between crossed polars [2V(-) = 30°, 20°, and 15°, respectively] and triclinic, as indicated by X-ray diffraction. The a sector is optically biaxial and orthorhombic. The c sector is optically uniaxial and essentially trigonal as indicated by single-crystal X-ray diffraction. The o, r, and c sectors are of liddicoatite component, whereas the a sector of the one specimen corresponds to fluor-elbaite. Another crystal specimen comprises a and m sectors, which are polysynthetically twinned, resulting in striations parallel to the c axis on the prism faces, and of liddicoatite. All five sectors have vacancies in the X-site (Ca, Na, □).

Original languageEnglish
Pages (from-to)364-369
Number of pages6
JournalAmerican Mineralogist
Volume86
Issue number3
Publication statusPublished - 2001 Jan 1

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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