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Iangreyite: a new secondary phosphate mineral closely related to perhamite

Published online by Cambridge University Press:  05 July 2018

S. J. Mills ,
A. R. Kampf ,
J. Sejkora ,
P. M. Adams ,
W. D. Birch  and
J. Plášil
S. J. Mills*
Affiliation:
Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA Geosciences, Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia
A. R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
J. Sejkora
Affiliation:
Department of Mineralogy and Petrology, National Museum Prague, Vaclavské nám. 68, CZ-115 79 Praha 1, Czech Republic
P. M. Adams
Affiliation:
126 South Helberta Avenue, #2, Redondo Beach, California 90277, USA
W. D. Birch
Affiliation:
Geosciences, Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia
J. Plášil
Affiliation:
Department of Mineralogy and Petrology, National Museum Prague, Vaclavské nám. 68, CZ-115 79 Praha 1, Czech Republic Department of Geological Sciences, Masaryk University, Kotlářská 2, Brno, 611 37, Czech Republic
*
*E-mail: smills@nhm.org
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Abstract

Iangreyite, ideally Ca2Al7(PO4)2(PO3OH)2(OH,F)15·8H2O, is a new mineral (IMA2009-087) from the Silver Coin mine, Nevada, USA and the Krásno ore district, Horní Slavkov, Czech Republic. At Silver Coin, iangreyite occurs as thin, colourless to white or cream, hexagonal tablets up to 0.4 mm in diameter and 0.02 mm thick associated with meurigite-Na, plumbogummite, kidwellite, lipscombite. strengite, chalcosiderite, wardite, leucophosphite, wavellite, goethite, barite, quartz and F-rich perhamite. At Krásno, white, yellowish or light pink iangreyite coatings consist of 0.3 mm wide clusters of minute and very thin intergrown tabular crystals with a maximum diameter of 0.2 mm. Individual iangreyite crystals are transparent with a vitreous lustre, while iangreyite clusters tend to be pearly and translucent. The estimated hardness is 3 on the Mohs scale, the fracture is irregular and the mineral is non-fluorescent under SW and LW ultraviolet light. Individual crystals are somewhat flexible and there is perfect cleavage on ﹛001﹜. The density (Silver Coin), measured by the sink-float method in an aqueous solution of sodium polytungstate, is 2.46(3) g/cm3, while the calculated density is 2.451 g/cm3. Crystals from Silver Coin are uniaxial (+), with the indices of refraction: ε = 1.544(2) and s = 1.554(2), measured in white light, and are non-pleochroic. The empirical formula for iangreyite from Silver Coin (calculated on the basis of 39 anions per formula unit) is: Ca1.42K0.22Na0.09Ba0.03 Sr0.01Al6.51Mg0.09Fe0.02Cu0.01Zn0.01P3.81F5.24H30.21O33.76, while the empirical formula from Krásno is: Ca2.15K0.10Na0.01Ba0.02Sr0.12Al6.28Mg0.01Fe0.12Cu0.08Zn0.01P3.64Si0.43F4.65H29.62O34.35. Iangreyite is trigonal, space group P321 and Z = 1, with the unit-cell parameters (Silver Coin): a = 6.988(1), c = 16.707(3) Å and V= 706.5(2) Å3 and (Krasno): a = 6.989(1), c = 16.782(4) Å and V = 709.8(2) Å3. The structure of iangreyite, modelled from powder data, consists of blocks of the crandallite-type structure that are interconnected along c via corner-sharing of crandallite-block PO4 tetrahedra with A1O2(OH)3 bipyramids. This linkage generates large channels along [110] bounded by 10-member rings of octahedra, tetrahedra and trigonal biyramids, that are occupied by Ca and water molecules.

Keywords

iangreyiteperhamitecrystal structurealunite supergroupnew mineralSilver Coin mineUSAKrásno ore districtCzech Republic
Type
CNMNC Newsletter 8
Information
Mineralogical Magazine , Volume 75 , Issue 2 , April 2011 , pp. 327 - 336
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2011

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