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Arsenoflorencite-(La), a new mineral from the Komi Republic, Russian Federation; description and crystal structure

Stuart J. Mills, Pavel M. Kartashov, Anthony R. Kampf and Mati Raudsepp
Arsenoflorencite-(La), a new mineral from the Komi Republic, Russian Federation; description and crystal structure
European Journal of Mineralogy (August 2010) 22 (4): 613-621

Abstract

Arsenoflorencite-(La) [Arsenflorensit-La], ideally LaAl (sub 3) (AsO (sub 4) ) (sub 2) (OH) (sub 6) , is a new mineral (IMA2009-078), from the Grubependity Lake cirque, Maldynyrd range, upper Kozhim River basin, Prepolar Ural, Komi Republic, Russia. It occurs in direct association with zircon, quartz, hematite, ardennite-(As), andalusite, anorthite, sericite, clinochlore, chernovite-(Y), manganiandrosite-(La), spessartine and monazite-gasparite-group minerals in Mn-rich nodules in metasediments. Arsenoflorencite-(La) forms orange-red to pink rhombohedral, pseudocubic or tabular crystals up to about 0.2 mm across. The dominant forms observed are {001} and {102}. The crystals have a vitreous lustre, are transparent to translucent, have a very light pink streak and are non-fluorescent. Mohs hardness is about 3.5 (estimated). The fracture is uneven and the tenacity is brittle. Arsenoflorencite-(La) has fair cleavage on {001}. Crystals are uniaxial (+), with the indices of refraction omega =1.740(5) and epsilon =1.750(5), measured in white light, and are nonpleochroic. The empirical formula (based on 14 O atoms) is: (La (sub 0.56) Ce (sub 0.18) Nd (sub 0.12) Pr (sub 0.04) Sr (sub 0.09) Ca (sub 0.03) ) (sub Sigma 1.02) (Al (sub 2.94) Fe (sub 0.06) ) (sub Sigma 3.00) (As (sub 1.80) P (sub 0.21) ) (sub Sigma 2.01) H (sub 5.95) O (sub 14) . The simplified formula is LaAl (sub 3) (AsO (sub 4) ) (sub 2) (OH) (sub 6) . Arsenoflorencite-(La) is trigonal, space group R3m, a=7.0316(3), c=16.5151(8) Aa, V=707.16(5) Aa (super 3) and Z=3. The crystal structure was solved from single-crystal X-ray diffraction data and refined to R (sub 1) =0.0112 on the basis of 287 unique reflections with F (sub o) >4sigma F and R (sub 1) =0.0116 for all 293 reflections. The five strongest lines in the powder X-ray diffraction pattern are [d (sub obs) in Aa, (I), (hkl)]: 2.982, (100), (113); 3.538, (55), (110); 1.914, (38), (303, 033); 2.211, (28), (122); 5.755, (27), (101). The name is for its relationship to florencite [and arsenoflorencite-(Ce)] with La as the dominant REE.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 22
Serial Issue: 4
Title: Arsenoflorencite-(La), a new mineral from the Komi Republic, Russian Federation; description and crystal structure
Affiliation: University of British Columbia, Department of Earth and Ocean Sciences, Vancouver, BC, Canada
Pages: 613-621
Published: 201008
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 27
Accession Number: 2010-081061
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N65°10'00" - N65°10'00", E60°15'00" - E60°15'00"
Secondary Affiliation: Russian Academy of Sciences, Institute of Geology Ore Deposits, Petrography, Mineralogy and Geochemistry, RUS, Russian FederationNatural History Museum of Los Angeles County, USA, United States
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201043
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