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Structural intergrowth of merlinoite/phillipsite and its temperature-dependent dehydration behaviour; a single-crystal X-ray study

Rosa Micaela Danisi, Thomas Armbruster and Mariko Nagashima
Structural intergrowth of merlinoite/phillipsite and its temperature-dependent dehydration behaviour; a single-crystal X-ray study
Mineralogical Magazine (February 2015) 79 (1): 191-203

Abstract

Supposed 'merlinoite' crystals from Monte Somma, Vesuvius (Italy) and Fosso Attici, north of Rome (Italy) represent highly twinned coherent intergrowths between merlinoite and phillipsite on a submicroscopic level. The MER (Immm, a nearly equal 14.1, b nearly equal 14.2, c nearly equal 9.9 Aa) and PHI (P2 (sub 1) /m, a nearly equal 9.9, b nearly equal 14.3, c nearly equal 8.7 Aa, beta = 124.8 degrees ) frameworks of similar composition are assembled from identical tetrahedral units, though with a different connectivity. Coherent intergrowth and twinning of the two frameworks lead to P4 (sub 2) /mnm pseudosymmetry, which is diagnostic of the intergrowth. Under ambient conditions merlinoite has Immm symmetry or I4/mmm if twinned. A low-symmetry model of space group P12 (sub 1) /m1 (a nearly equal 14.2, b nearly equal 14.2, c nearly equal 10 Aa, beta = 90 degrees ) allows structure refinement and quantification of the two frameworks.Upon in situ dehydration to 250 degrees C the evolution of the unit-cell volume of the Monte Somma merlinoite/phillipsite intergrowth displays an intermediate trend between previously studied pure merlinoite from the Khibiny massif (Russia) and Ba-rich phillipsite.The Monte Somma crystal studied by temperature-dependent single-crystal X-ray diffraction methods also contained a subordinate chabazite inclusion with no coherent structural relationship to the merlinoite/phillipsite framework. Thus, the modification of the chabazite framework on dehydration could also be studied.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 1
Title: Structural intergrowth of merlinoite/phillipsite and its temperature-dependent dehydration behaviour; a single-crystal X-ray study
Affiliation: University of Bern, Institute of Geological Sciences, Bern, Switzerland
Pages: 191-203
Published: 201502
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 20
Accession Number: 2015-061813
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N67°00'00" - N68°00'00", E33°00'00" - E34°00'00"
N40°49'60" - N40°49'60", E14°25'60" - E14°25'60"
N37°00'00" - N83°00'00", W170°00'00" - E28°00'00"
N40°49'00" - N40°49'00", E14°25'60" - E14°25'60"
Secondary Affiliation: Yamaguchi University, JPN, Japan
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201527
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