Almeidaite, Pb(Mn,Y)Zn2(Ti,Fe3+)18O36(O,OH)2, a new crichtonite-group mineral, from Novo Horizonte, Bahia, Brazil

Autor:	Nikita V. Chukanov, Antônio W. Romano, Luiz A.D. Menezes Filho, Luiz C.A. Oliveira, Mario Luiz de Sá Carneiro Chaves, Daniel Atencio, Igor V. Pekov, Roberto L. Moreira, A. I. C. Persiano, Ramiza K. Rastsvetaeva, Frederico Sousa Guimarães, Paulo Roberto Gomes Brandão, Ricardo Scholz, José D. Ardisson, Sergey M. Aksenov, R. Peter Richards, Klaus Krambrock
Rok vydání:	2015
Předmět:	Hexagonal prism Anatase Mineral Materials science Muscovite 05 social sciences Crystal structure engineering.material Crystallography Geochemistry and Petrology 0502 economics and business engineering Kaolinite 050211 marketing Quartz Chemical composition 050203 business & management
Zdroj:	Mineralogical Magazine. 79:269-283
ISSN:	1471-8022 0026-461X
DOI:	10.1180/minmag.2015.079.2.06
Popis:	Almeidaite (IMA 2013-020), ideally Pb(Mn, Y)Zn2(Ti,Fe3+)18O36(O, OH)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 6 30 mm 6 6 mm in size, dominated by the basal pinacoid {0001}, which is bounded by various, mostly steep, rhombohedra and the hexagonal prism {1120}. 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 [(Ro, Re) λ (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 (Pb0.59Sr0.12Ca0.04La0.03)Σ0.78(Mn0.54Y0.46)Σ1.00Zn1.43(Ti13.02Fe4.983+)Σ18.00(Fe0.323+Mn0.15)Σ0.47[O37.18(OH)0.82]Σ38.00. It is trigonal, space group R3, with the unit-cell parameters a = 10.4359(2), c = 21.0471(4) Å, V = 1985.10(7) Å3 and Z = 3. The crystal structure was solved (R1 = 0.039) using 2110 unique reflections with I > 3σ(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 Flávio Marques de Almeida (1916–2013).
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::0df1d8b7de61872a3505392daee62b83 https://doi.org/10.1180/minmag.2015.079.2.06 Zobrazit plný text záznamu