Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia

William Mumme; Ian Grey; W Birch; Allan Pring; Catherine Bougerol; N Wilson

doi:10.2138/am.2010.3360

Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia

William Mumme, Ian Grey, W Birch, Allan Pring, Catherine Bougerol, N Wilson

Research output: Contribution to journal › Article

6 Citations (Scopus)

Abstract

Coulsellite, CaNa₃AlMg₃F₁₄, from the Cleveland tin mine at Luina, western Tasmania, has a rhombohedral distortion of the cubic pyrochlore A₂B₂X₆Y structure, with a = 7.1756(1) Å, α = 59.867(1)°, space group R3̄m, Z = 1. The corresponding hexagonal cell parameters are a = 7.1620(1) Å, c = 17.5972(3) Å. The crystals are multiply twinned about threefold axes of the pseudocubic cell. The structure was determined using X-ray data collected on a twinned crystal and refined to Robs = 0.027 for 452 observed reflections with I > 2σ(I). The structure is possibly unique among published structures of pyrochlore-like minerals in having full 1:3 ordering of Ca:Na in the A sites and Al:Mg in the B sites. Transmission electron photomicrographs show a nanodomain structure due to twinning on a scale of ∼5 nm.

Original language	English
Pages (from-to)	736-740
Number of pages	5
Journal	American Mineralogist
Volume	95
Issue number	5-6
DOIs	https://doi.org/10.2138/am.2010.3360
Publication status	Published - May 2010

Keywords

1:3 cation ordering in CaNa AlMg F
New fluoride mineral
Rhombohedral pyrochlore
Structure determination

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Mumme, W., Grey, I., Birch, W., Pring, A., Bougerol, C., & Wilson, N. (2010). Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia. American Mineralogist, 95(5-6), 736-740. https://doi.org/10.2138/am.2010.3360

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title = "Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia",

abstract = "Coulsellite, CaNa3AlMg3F14, from the Cleveland tin mine at Luina, western Tasmania, has a rhombohedral distortion of the cubic pyrochlore A2B2X6Y structure, with a = 7.1756(1) {\AA}, α = 59.867(1)°, space group R{\=3}m, Z = 1. The corresponding hexagonal cell parameters are a = 7.1620(1) {\AA}, c = 17.5972(3) {\AA}. The crystals are multiply twinned about threefold axes of the pseudocubic cell. The structure was determined using X-ray data collected on a twinned crystal and refined to Robs = 0.027 for 452 observed reflections with I > 2σ(I). The structure is possibly unique among published structures of pyrochlore-like minerals in having full 1:3 ordering of Ca:Na in the A sites and Al:Mg in the B sites. Transmission electron photomicrographs show a nanodomain structure due to twinning on a scale of ∼5 nm.",

keywords = "1:3 cation ordering in CaNa AlMg F, New fluoride mineral, Rhombohedral pyrochlore, Structure determination",

author = "William Mumme and Ian Grey and W Birch and Allan Pring and Catherine Bougerol and N Wilson",

year = "2010",

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AU - Mumme, William

AU - Grey, Ian

AU - Birch, W

AU - Pring, Allan

AU - Bougerol, Catherine

AU - Wilson, N

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N2 - Coulsellite, CaNa3AlMg3F14, from the Cleveland tin mine at Luina, western Tasmania, has a rhombohedral distortion of the cubic pyrochlore A2B2X6Y structure, with a = 7.1756(1) Å, α = 59.867(1)°, space group R3̄m, Z = 1. The corresponding hexagonal cell parameters are a = 7.1620(1) Å, c = 17.5972(3) Å. The crystals are multiply twinned about threefold axes of the pseudocubic cell. The structure was determined using X-ray data collected on a twinned crystal and refined to Robs = 0.027 for 452 observed reflections with I > 2σ(I). The structure is possibly unique among published structures of pyrochlore-like minerals in having full 1:3 ordering of Ca:Na in the A sites and Al:Mg in the B sites. Transmission electron photomicrographs show a nanodomain structure due to twinning on a scale of ∼5 nm.

AB - Coulsellite, CaNa3AlMg3F14, from the Cleveland tin mine at Luina, western Tasmania, has a rhombohedral distortion of the cubic pyrochlore A2B2X6Y structure, with a = 7.1756(1) Å, α = 59.867(1)°, space group R3̄m, Z = 1. The corresponding hexagonal cell parameters are a = 7.1620(1) Å, c = 17.5972(3) Å. The crystals are multiply twinned about threefold axes of the pseudocubic cell. The structure was determined using X-ray data collected on a twinned crystal and refined to Robs = 0.027 for 452 observed reflections with I > 2σ(I). The structure is possibly unique among published structures of pyrochlore-like minerals in having full 1:3 ordering of Ca:Na in the A sites and Al:Mg in the B sites. Transmission electron photomicrographs show a nanodomain structure due to twinning on a scale of ∼5 nm.

KW - 1:3 cation ordering in CaNa AlMg F

KW - New fluoride mineral

KW - Rhombohedral pyrochlore

KW - Structure determination

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