The crystal structure of ingersonite, Ca3Mn2+Sb45+O14, and its relationships with pyrochlore

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doi: 10.2138/am.2007.2421
Authors:Bonazzi, Paola; Bindi, Luca
Author Affiliations:Primary:
Universita di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Volume Title:American Mineralogist
Source:American Mineralogist, 92(5-6), p.947-953. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2007
Note:In English. 28 refs.; illus., incl. 7 tables
Summary:The crystal structure of ingersonite, [Ca2.93Mn2+1.06Fe2+0.01] [Sb5+3.95Mg0.05]F0.15O13.85, has been solved and refined in the space group P3121 [a = 7.282(2), c = 17.604(4) Å, V = 808.4(3) Å3, Z = 3] to R = 2.32% for 2219 Fo>4σ(Fo) using MoKα X-ray data. The structure of ingersonite is isostructural with the synthetic weberite-3T polytype and related to the pyrochlore structure type. Both ingersonite and pyrochlore structures can be described as a sequence of pairs of polyhedral layers (named M and N), stacked along [111] and [001], respectively. In terms of the cation sites, M and N layers have general formula AB3 and A3B, respectively, where B are the octahedral cations forming the B2X6 framework of the pyrochlore structure and A are the larger, interstitial cations forming eightfold polyhedra in pyrochlore. In ingersonite, the M layers occur at z approximately 1/6, 1/2, and 5/6: The B octahedra are occupied by Sb5+ and share corners to form a pseudohexagonal tungsten bronze (HTB) motif with the A position occupied by octahedral Mn2+ at the center of the pseudohexagonal rings. N layers occur at z approximately 0, 1/3, and 2/3, with A = Ca and B = Sb5+: Isolated B octahedra share 6 edges with 6 eightfold A polyhedra, to form a continuous sheet similar to the analogous layer in pyrochlore. The stacking of successive pairs of M and N layers in ingersonite is the same as in pyrochlore. Nonetheless, a difference in the relative position between M and N layers in ingersonite and pyrochlore is observed. The crystal-chemical relationships with other pyrochlore-related minerals are outlined.
Sections:Crystal structure
Subjects:Antimonates; Antimony; Crystal structure; Fluorides; Halides; Metals; Polytypism; Pyrochlore; Synthetic materials; Weberite; Europe; Scandinavia; Sweden; Varmland Sweden; Western Europe; Ingersonite; Langban Mine
Abstract Numbers:07M/2193
Record ID:2007065448
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, copyright, Mineralogical Society of America, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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