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Pilawite-(Y), Ca (sub 2) (Y, Yb) (sub 2) [Al (sub 4) (SiO (sub 4) ) (sub 4) O (sub 2) (OH) (sub 2) ], a new mineral from the Pilawa Gorna granitic pegmatite, southwestern Poland; mineralogical data, crystal structure and association

Adam Pieczka, Frank C. Hawthorne, Mark A. Cooper, Eligiusz Szeleg, Adam Szuszkiewicz, Krzysztof Turniak, Krzysztof Nejbert and Slawomir Ilnicki
Pilawite-(Y), Ca (sub 2) (Y, Yb) (sub 2) [Al (sub 4) (SiO (sub 4) ) (sub 4) O (sub 2) (OH) (sub 2) ], a new mineral from the Pilawa Gorna granitic pegmatite, southwestern Poland; mineralogical data, crystal structure and association
Mineralogical Magazine (November 2015) 79 (5): 1143-1157

Abstract

Pilawite-(Y), ideally Ca (sub 2) (Y,Yb) (sub 2) Al (sub 4) (SiO (sub 4) ) (sub 4) O (sub 2) (OH) (sub 2) , was discovered in a pegmatite near Pilawa Gorna, Lower Silesia, Poland. The mineral occurs as white, translucent, brittle crystals up to 1.5 mm in size. It has a white streak, vitreous lustre and a hardness of 5 on Mohs scale. The calculated density is 4.007 g/cm (super 3) . Pilawite-(Y) is non-pleochroic, biaxial (+), with refractive indices alpha =1.743(5), beta =1.754(5) and gamma =1.779(5), birefringence Delta =0.03-0.04, 2V (sub meas.) =65(2) degrees and 2V (sub calc.) =68 degrees . Pilawite-(Y) is monoclinic P2 (sub 1) /c, with unit-cell parameters a=8.558(3) Aa, b=7.260(3) Aa, c=11.182(6) Aa, beta =90.61(4) degrees , V=694.7(4) Aa (super 3) . The crystal structure was refined to an R1 index of 2.76% and consists of chains of edge- and corner-sharing octahedra decorated by tetrahedra and having the stoichiometry [Al (sub 2) (SiO (sub 4) ) (sub 4) O(OH)] that link by sharing corners to form an octahedron-tetrahedron framework with large interstices that contain Ca (super 2+) and (Y,Ln) (super 3+) . It is a graphical isomer of the Al-P framework in palermoite, Sr (sub 2) Li (sub 4) [Al (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) ] (sub 2) . The pilawite-(Y)-bearing assemblage began crystallization at high Y + Ln activities and was modified progressively by a Ca-enriched fluid, resulting in the sequence: keiviite-(Y) --> gadolinite-(Y) to hingganite-(Y)+hellandite-(Y) --> pilawite-(Y) --> allanite-(Y) --> epidote/zoisite.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 5
Title: Pilawite-(Y), Ca (sub 2) (Y, Yb) (sub 2) [Al (sub 4) (SiO (sub 4) ) (sub 4) O (sub 2) (OH) (sub 2) ], a new mineral from the Pilawa Gorna granitic pegmatite, southwestern Poland; mineralogical data, crystal structure and association
Affiliation: AGH University of Science and Technology, Department of Mineralogy, Petrography and Geochemistry, Cracow, Poland
Pages: 1143-1157
Published: 201511
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 31
Accession Number: 2016-007400
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N50°34'60" - N50°45'00", E16°40'00" - E16°49'60"
Secondary Affiliation: University of Manitoba, CAN, CanadaUniversity of Silesia, POL, PolandUniversity of Wroclaw, POL, Poland
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201604
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