| Texto completo | |
| Autor(es): Mostrar menos - |
Menezes Filho, Luiz A. D.
[1]
;
Chukanov, Nikita V.
[2]
;
Rastsvetaeva, Ramiza K.
[3]
;
Aksenov, Sergey M.
[3]
;
Pekov, Igor V.
[4]
;
Chaves, Mario L. S. C.
[1]
;
Richards, R. Peter
[5]
;
Atencio, Daniel
[6]
;
Brandao, Paulo R. G.
[7]
;
Scholz, Ricardo
[8]
;
Krambrock, Klaus
[9]
;
Moreira, Roberto L.
[9]
;
Guimaraes, Frederico S.
[9]
;
Romano, Antonio W.
[1]
;
Persiano, Aba C.
[9]
;
de Oliveira, Luiz C. A.
[10]
;
Ardisson, Jose D.
[11]
Número total de Autores: 17
|
| Afiliação do(s) autor(es): Mostrar menos - | [1] Univ Fed Minas Gerais, Inst Geociencias, BR-31270902 Belo Horizonte, MG - Brazil
[2] Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region - Russia
[3] Russian Acad Sci, Inst Crystallog, Moscow 117333 - Russia
[4] Moscow MV Lomonosov State Univ, Fac Geol, Moscow 119991 - Russia
[5] Oberlin Coll, Dept Geol, Oberlin, OH 44074 - USA
[6] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo, SP - Brazil
[7] Univ Fed Minas Gerais, Escola Engn, Dept Engn Minas, BR-31270902 Belo Horizonte, MG - Brazil
[8] Univ Fed Ouro Preto, Escola Minas, Dept Geol, BR-35400000 Ouro Preto, MG - Brazil
[9] Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Fis, BR-31270901 Belo Horizonte, MG - Brazil
[10] Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Quim, BR-31270901 Belo Horizonte, MG - Brazil
[11] CNEN CDTN SENAN Lab Aplicada Fis, BR-31270901 Belo Horizonte, MG - Brazil
Número total de Afiliações: 11
|
| Tipo de documento: | Artigo Científico |
| Fonte: | MINERALOGICAL MAGAZINE; v. 79, n. 2, p. 269-283, APR 2015. |
| Citações Web of Science: | 3 |
| Resumo | |
Almeidaite (IMA 2013-020), ideally Pb(Mn,Y)Zn-2(Ti,Fe3+)(18)O36(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 mmx30 mmx6 mm in size, dominated by the basal pinacoid [0001], which is bounded by various, mostly steep, rhombohedra and the hexagonal prism [11 (2) over bar0]. 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-o, R-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 (Pb0.59Sr0.12Ca0.04La0.03)(Sigma 0.78)(Mn0.54Y0.46)(Sigma 1.00)Zn-1.43(Ti13.02Fe4.983+)(Sigma 18.00)(Fe0.323+Mn0.15)(Sigma 0.47) {[}O-37.18(OH)(0.82)](Sigma 38.00). It is trigonal, space group R (3) over bar, with the unit-cell parameters a = 10.4359(2), c = 21.0471(4) angstrom, V = 1985.10(7) angstrom(3) and Z = 3. The crystal structure was solved (R-1 = 0.039) using 2110 unique reflections with I > 3 sigma(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). (AU) | |
| Processo FAPESP: | 11/22407-0 - Caracterização de espécies minerais brasileiras novas e raras |
| Beneficiário: | Daniel Atencio |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |