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Bendadaite, a new iron arsenate mineral of the arthurite group

Uwe Kolitsch, Daniel Atencio, N. V. Chukanov, N. V. Zubkova, L. A. D. Menezes Filho, J. M. V. Coutinho, W. D. Birch, J. Schlueter, D. Pohl, Anthony R. Kampf, I. M. Steele, G. Favreau, L. Nasdala, S. Moeckel, G. Giester and D. Yu. Pushcharovsky
Bendadaite, a new iron arsenate mineral of the arthurite group
Mineralogical Magazine (June 2010) 74 (3): 469-486


Bendadaite, ideally Fe (super 2+) Fe (super 3+) (sub 2) (AsO (sub 4) ) (sub 2) (OH) (sub 2) .4H (sub 2) O, is a new member of the arthurite group. It was found as a weathering product of arsenopyrite on a single hand specimen from the phosphate pegmatite Bendada, central Portugal (type locality). Co-type locality is the granite pegmatite of Lavra do Almerindo (Almerindo mine), Linopolis, Divino das Laranjeiras county, Minas Gerais, Brazil. Further localities are the Veta Negra mine, Copiapo province, Chile; Oumlil-East, Bou Azzer district, Morocco; and Pira Inferida yard, Fenugu Sibiri mine, Gonnosfanadiga, Medio Campidano Province, Sardinia, Italy. Type bendadaite occurs as blackish green to dark brownish tufts (<0.1 mm long) and flattened radiating aggregates, in intimate association with an intermediate member of the scorodite-mansfieldite series. It is monoclinic, space group P2 (sub 1) /c, with a=10.239(3) Aa, b=9.713(2) Aa, c=5.552(2) Aa, beta =94.11(2) degrees , V=550.7(2) Aa (super 3) , Z=2. Electron-microprobe analysis yielded (wt.%): CaO 0.04, MnO 0.03, CuO 0.06, ZnO 0.04, Fe (sub 2) O (sub 3) (total) 43.92, Al (sub 2) O (sub 3) 1.15, SnO (sub 2) 0.10, As (sub 2) O (sub 5) 43.27, P (sub 2) O (sub 5) 1.86, SO (sub 3) 0.03. The empirical formula is Fe (super 2+) (sub 0.52) Fe (super 3+) (sub 0.32) [] (sub 0.16) ) (sub Sigma 1.00) (Fe (super 3+) (sub 1.89) Al (sub 0.11) ) (sub Sigma 2.00) (As (sub 1.87) P (sub 0.13) ) (sub Sigma 2.00) O (sub 8) (OH) (sub 2.00) .4H (sub 2) O, based on 2(As,P) and assuming ideal 8O, 2(OH), 4H (sub 2) O and complete occupancy of the ferric iron site by Fe (super 3+) and Al. Optically, bendadaite is biaxial, positive, 2V (sub est.) =85S4 degrees , 2V (sub calc.) =88 degrees , with alpha 1.734(3), beta 1.759(3), gamma 1.787(4). Pleochroism is medium strong: X pale reddish brown, Y yellowish brown, Z dark yellowish brown; absorption Z>Y>X, optical dispersion weak, r>v. Optical axis plane is parallel to (010), with X approximately parallel to a and Z nearly parallel to c. Bendadaite has vitreous to sub-adamantine luster, is translucent and non-fluorescent. It is brittle, shows irregular fracture and a good cleavage parallel to {010}. D (sub meas.) 3.15+ or -0.10 g/cm (super 3) , D (sub calc.) 3.193 g/cm (for the empirical formula). The five strongest powder diffraction lines [d in Aa (I)(hkl)] are 10.22 (10)(100), 7.036 (8)(110), 4.250 (5)(111), 2.865 (4)(311), 4.833 (3)(020,011). The d spacings are very similar to those of its Zn analogue, ojuelaite. The crystal structure of bendadaite was solved and refined using a crystal from the co-type locality with the composition Fe (super 2+) (sub 0.95) [] (sub 0.05) ) (sub Sigma 1.00) (Fe (super 3+) (sub 1.80) Al (sub 0.20) ) (sub Sigma 2.00) (As (sub 1.48) P (sub 0.52) ) (sub Sigma 2.00) O (sub 8) (OH) (sub 2) .4H (sub 2) O (R=1.6%), and confirms an arthurite-type atomic arrangement.

ISSN: 0026-461X
EISSN: 1471-8022
Serial Title: Mineralogical Magazine
Serial Volume: 74
Serial Issue: 3
Title: Bendadaite, a new iron arsenate mineral of the arthurite group
Affiliation: Naturhistorisches Museum, Mineralogisch-Petrographische Abteilung, Vienna, Austria
Pages: 469-486
Published: 201006
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 42
Accession Number: 2010-068333
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N30°34'60" - N30°34'60", W06°45'00" - W06°45'00"
S23°30'00" - S14°00'00", W51°00'00" - W39°45'00"
N37°00'00" - N42°10'00", W09°30'00" - W06°10'00"
N38°49'60" - N41°30'00", E08°15'00" - E09°45'00"
Secondary Affiliation: Universitaet Wien, AUT, AustriaUniversidade de Sao Paulo, BRA, BrazilInstitute for Chemical Physics, RUS, Russian FederationMoscow State University, RUS, Russian FederationUniversidade Federal de Minas Gerais, BRA, BrazilMuseum Victoria, AUS, AustraliaUniversitaet Hamburg, DEU, Federal Republic of GermanyNatural History Museum of Los Angeles County, USA, United StatesUniversity of Chicago, USA, United States
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201037
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