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Almeidaite, Pb(Mn,Y)Zn (sub 2) (Ti,Fe (super 3+) ) (sub 18) O (sub 36) (O,OH) (sub 2) ; a new crichtonite-group mineral, from Novo Horizonte, Bahia, Brazil

Luiz A. D. Menezes Filho, Nikita V. Chukanov, Ramiza K. Rastsvetaeva, Sergey M. Aksenov, Igor V. Pekov, Mario L. S. C. Chaves, R. Peter Richards, Daniel Atencio, Paulo R. G. Brandao, Ricardo Scholz, Klaus Krambrock, Roberto L. Moreira, Frederico S. Guimaraes, Antonio W. Romano, Aba C. Persiano, Luiz C. A. de Oliveira and Jose D. Ardisson
Almeidaite, Pb(Mn,Y)Zn (sub 2) (Ti,Fe (super 3+) ) (sub 18) O (sub 36) (O,OH) (sub 2) ; a new crichtonite-group mineral, from Novo Horizonte, Bahia, Brazil
Mineralogical Magazine (April 2015) 79 (2): 269-283

Abstract

Almeidaite (IMA 2013-020), ideally Pb(Mn,Y)Zn (sub 2) (Ti,Fe (super 3+) ) (sub 18) O (sub 36) (O,OH) (sub 2) , from Novo Horizonte, Bahia, Brazil, occurs in association with quartz, rutile, anatase, hematite, kaolinite, muscovite, xenotime-(Y) and bastnaesite-(La). Almeidaite forms isolated, black, opaque, sub-metallic, platy crystals flattened on [0001], measuring up to 30 mm X 30 mm X 6 mm in size, dominated by the basal pinacoid {0001}, which is bounded by various, mostly steep, rhombohedra and the hexagonal prism {112I0}. Most of the crystals are multiply twinned, with non-planar contact surfaces that are approximately parallel to the c axis. The streak is brown. Reflectance values are [(R (sub o) , R (sub e) ) lambda (nm)]: (12.78, 15.39) 470; (12.86, 15.43) 546; (12.91, 15.55) 589; (13.04, 15.75) 650. The empirical formula is (Pb (sub 0.59) Sr (sub 0.12) Ca (sub 0.04) La (sub 0.03) ) (sub Sigma 0.78) (Mn (sub 0.54) Y (sub 0.46) ) (sub Sigma 1.00) Zn (sub 1.43) (Ti (sub 13.02) [Fe (super 3+) (sub 4.98) ) (sub Sigma 18.00) (Fe (super 3+) (sub 0.32) Mn (sub 0.15) ) (sub Sigma 0.47) [O (sub 37.18) (OH) (sub 0.82) ] (sub Sigma 38.00) . It is trigonal, space group R3I, with the unit-cell parameters a = 10.4359(2), c = 21.0471(4) Aa, V = 1985.10(7) Aa (super 3) and Z = 3. The crystal structure was solved (R (sub 1) = 0.039) using 2110 unique reflections with I > 3sigma (I). Almeidaite is a member of the crichtonite group with Pb dominant in the A site (with 12-fold coordination) and Zn dominant in the T site (with 4-fold coordination). It is a Zn analogue of senaite and a Pb analogue of landauite. The mineral is named after Professor Fernando Flavio Marques de Almeida (1916-2013).


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 2
Title: Almeidaite, Pb(Mn,Y)Zn (sub 2) (Ti,Fe (super 3+) ) (sub 18) O (sub 36) (O,OH) (sub 2) ; a new crichtonite-group mineral, from Novo Horizonte, Bahia, Brazil
Affiliation: Universidade Federal de Minas Gerais, Instituto de Geociencias, Belo Horizonte, Brazil
Pages: 269-283
Published: 201504
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 28
Accession Number: 2015-070044
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 12 tables
S18°19'60" - S08°19'60", W46°40'00" - W37°19'60"
Secondary Affiliation: Russian Academy of Sciences, Institute of Problems of Chemical Physics, RUS, Russian FederationRussian Academy of Sciences, Institute of Crystallography, RUS, Russian FederationMoscow State University, RUS, Russian FederationOberlin College, USA, United StatesUniversidade de Sao Paulo, BRA, BrazilUniversidade Federal de Ouro Preto, BRA, BrazilCentro de Desenvolvimento da Tecnologia Nuclear, BRA, Brazil
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: 201530
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