Cesarferreiraite, Fe2+Fe23+(AsO4)(2)(OH)(2)center dot 8H(2)O, from Eduardo mine, Conselheiro Pena, Minas Gerais, Brazil: Second arsenate in the laueite mineral group

Author(s):Show less -

Scholz, Ricardo ^[1] ; Chukanov, Nikita V. ^[2] ; Menezes Filho, Luiz A. D. ^[3] ; Atencio, Daniel ^[4] ; Lagoeiro, Leonardo ^[1] ; Belotti, Fernanda M. ^[5] ; Chaves, Mario L. S. C. ^[3] ; Romano, Antonio W. ^[3] ; Brandao, Paulo R. ^[6] ; Belakovskiy, Dmitriy I. ^[7] ; Pekov, Igor ^[8]

Affiliation

^[1] Univ Fed Ouro Preto, Dept Geol, Escola Minas, BR-35400000 Ouro Preto, MG - Brazil

^[2] Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region - Russia

^[3] Univ Fed Minas Gerais, Inst Geociencias, BR-31270901 Belo Horizonte, MG - Brazil

^[4] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[5] Univ Fed Itajuba UNIFEI, Itabira, MG - Brazil

^[6] Univ Fed Minas Gerais, Escola Engn, BR-31270901 Belo Horizonte, MG - Brazil

^[7] Russian Acad Sci, Fersman Mineral Museum, Moscow 117071 - Russia

^[8] Moscow MV Lomonosov State Univ, Fac Geol, Moscow 119899 - Russia

• Document type: Journal article
• Source: AMERICAN MINERALOGIST; v. 99, n. 4, p. 607-611, APR 2014.
• Web of Science Citations: 8

Abstract

Cesarferreiraite, Fe2+Fe23+(AsO4)(2)(OH)(2)center dot 8H(2)O, is a new laueite-group mineral (IMA 2012-099) of triclinic symmetry, from Eduardo pegmatite mine, Conselheiro Pena municipality, Minas Gerais. Brazil. Intimately associated minerals are pharmacosiderite, scorodite. and earlier arsenopyrite, and probably cesarferreiraite replaces the latter. It occurs as fibrous-to-tabular aggregates up to 2 mm. Single crystals, up to 10 Inn long with a thickness of about 1-2 mu m are elongated along {[}001] and flattened on (100). The fibers have almost rectangular cross-section apparently bound by the [100] and [010] pinacoid forms. Color and streak are pale to greenish yellow. Luster is vitreous; individual crystals are transparent and masses are translucent. Cleavage is distinct, presumably on [010] and [100]. Calculated density is 2.934 g/cm(3). The mineral is biaxial (+), a (min) = 1.747(3), n (max) = 1.754(3) (589 nm). IR spectrum of cesafferreiraite is unique and can be used for the identification of the mineral. Chemical composition (n = 4, WDS, calculated for the condition Fe2+:Fe3+ = 1:2, H2O for the ideal structural formula, wt%) is: FeO 11.50, Fe2O3 25.56, CaO 15.41, As2O5 33.51, H2O 26.01, total 100.12. The empirical formula (based on 18 O apfu) is Fe0.982+Fe1.963+{[}(AsO)(4))(179)(PO4)(0.31)](OH)(152)center dot 8.08H(2)O. The strongest eight X-ray powder-diffraction lines {[}d in angstrom(l)(hkl)] are: 9.85(95)(010), 6.35(100)(001), 3.671(29)((1) over bar 21), 3.158(32)(1 (3) over bar0), 2.960(39)(02 (2) over bar), 2.884(35)((1) over bar 31), 2.680(29)((2) over bar 11), and 2.540(23)((2) over bar 10). Unit-cell parameters refined from powder data indexed by analogy with related laueite-group minerals (space group: P (1) over bar) are: a = 5.383(2) , b = 10.363(3), c = 6.878(2) angstrom, alpha = 96.42(4), beta = 109.19(3), gamma = 102.30(2)degrees, V= 347.1(2) angstrom(3), and Z= 1. Gladstone-Dale compatibility is -0.020 (excellent). Cesarferreiraite is the arsenate analog of ferrolaueite. (AU)

• FAPESP's process: 11/22407-0 - New and rare Brazilian mineral species characterization
• Grantee: Daniel Atencio
• Support Opportunities: Regular Research Grants