Luiz Alberto Dias Menezes Filho

Césarferreiraite, Fe2+Fe23+(AsO4)2(OH)2·8H2O, from Eduardo mine, Conselheiro Pena, Minas Gerais, Brazil: Second arsenate in the laueite mineral group

Abstract Césarferreiraite, Fe2+Fe23+(AsO4)2(OH)2·8H2O, 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 césarferreiraite replaces the latter. It occurs as fibrous-to-tabular aggregates up to 2 mm. Single crystals, up to 10 μm long with a thickness of about 1-2 μm, 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/cm3. The mineral is biaxial (+), n (min) = 1.747(3), n (max) = 1.754(3) (589 nm). IR spectrum of césarferreiraite 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 Fe2+0.98Fe3+1.96[(AsO4)1.79(PO4)0.31](OH)1.52·8.08H2O. The strongest eight X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 9.85(95)(010), 6.35(100)(001), 3.671(29)(1̅21), 3.158(32)(13̅0), 2.960(39)(022̅), 2.884(35)(1̅31), 2.680(29)(2̅11), and 2.540(23)(2̅10). Unit-cell parameters refined from powder data indexed by analogy with related laueite-group minerals (space group: P1̅) are: a = 5.383(2), b = 10.363(3), c = 6.878(2) Å, α = 96.42(4), β = 109.19(3), γ = 102.30(2)°, V = 347.1(2) Å3, and Z = 1. Gladstone-Dale compatibility is -0.020 (excellent). Césarferreiraite is the arsenate analog of ferrolaueite.

A vibrational spectroscopic study of the phosphate mineral zanazziite – Ca2(MgFe2+)(MgFe2+Al)4Be4(PO4)6⋅6(H2O)

Zanazziite is the magnesium member of a complex beryllium calcium phosphate mineral group named roscherite. The studied samples were collected from the Ponte do Piauí mine, located in Itinga, Minas Gerais. The mineral was studied by electron microprobe, Raman and infrared spectroscopy. The chemical formula can be expressed as Ca(2.00)(Mg(3.15),Fe(0.78),Mn(0.16),Zn(0.01),Al(0.26),Ca(0.14))Be(4.00)(PO(4))(6.09)(OH)(4.00)⋅5.69(H(2)O) and shows an intermediate member of the zanazziite-greinfeinstenite series, with predominance of zanazziite member. The molecular structure of the mineral zanazziite has been determined using a combination of Raman and infrared spectroscopy. A very intense Raman band at 970 cm(-1) is assigned to the phosphate symmetric stretching mode whilst the Raman bands at 1007, 1047, 1064 and 1096 cm(-1) are attributed to the phosphate antisymmetric stretching mode. The infrared spectrum is broad and the antisymmetric stretching bands are prominent. Raman bands at 559, 568, 589 cm(-1) are assigned to the ν(4) out of plane bending modes of the PO(4) and HPO(4) units. The observation of multiple bands supports the concept that the symmetry of the phosphate unit in the zanazziite structure is reduced in symmetry. Raman bands at 3437 and 3447 cm(-1) are attributed to the OH stretching vibrations; Raman bands at 3098 and 3256 are attributed to water stretching vibrations. The width and complexity of the infrared spectral profile in contrast to the well resolved Raman spectra, proves that the pegmatitic phosphates are better studied with Raman spectroscopy.

Correianevesite, Fe2+Mn22+(PO4)2·3H2O, a new reddingite-group mineral from the Cigana mine, Conselheiro Pena, Minas Gerais, Brazil

Abstract Correianevesite, ideally Fe2+Mn22+(PO4)2·3H2O, is a new reddingite-group mineral approved by the CNMNC (IMA 2013-007). It occurs in a phosphate-rich granite pegmatite that outcrops near the Cigana mine, Conselheiro Pena, Rio Doce valley, Minas Gerais, Brazil. Associated minerals are: triphylite, lithiophilite, frondelite, rockbridgeite, eosphorite, vivianite, fairfieldite, leucophosphite, cyrilovite, phosphosiderite, etc. Correianevesite occurs as grayish-brown to reddish-brown transparent bipyramidal crystals up to 4 mm in size. The streak is white, and the luster is vitreous. Mohs hardness is 3½. Cleavage is poor on (010). Fracture is laminated, uneven across cleavage. The measured density is 3.25(2) g/cm3; the calculated density is 3.275 g/cm3. The mineral is biaxial (+), α = 1.661(5), β = 1.673(5), γ = 1.703(5), 2Vmeas = 70(10)°, 2Vcalc = 65.6°. The IR spectrum confirms the presence of H2O. The Mössbauer spectrum shows the presence of two sites for Fe2+ and one site for Fe3+ occupied in the ratio Fe12+:Fe22+:Fe3+ = 39:55:6. The chemical composition is as follows (electron microprobe, H2O determined by gas chromatography of ignition products, Fe apportioned between FeO and Fe2O3 based on Mössbauer data, wt%): MnO 29.21, FeO 21.74, Fe2O3 1.54, P2O5 34.59, H2O 12.6, total 99.68. The empirical formula, based on 11 O apfu, is H5.78Mn1.70Fe2+1.25Fe3+0.08P2.015O11. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 5.08 (43) (020), 4.314 (28) (002, 210), 3.220 (100) (221, 202), 3.125 (25) (122), 2.756 (35) (103, 230), 2.686 (25) (222, 113), 2.436 (22) (123), and 2.233 (23) (411, 331). The crystal structure is solved (R1 = 0.0176). Correianevesite is orthorhombic, space group Pbna, a = 9.4887(2), b = 10.1149(2), c = 8.7062(2) Å, V = 835.60(3) Å3, Z = 4. The refined crystal-chemical formula is: (Fe2+0.72Mn2+0.20Fe3+0.08)(Mn1.48Fe2+0.52)(PO4)2 (H2O,OH)3.

Pauloabibite, trigonal NaNbO3, isostructural with ilmenite, from the Jacupiranga carbonatite, Cajati, São Paulo, Brazil

Abstract Pauloabibite (IMA 2012-090), trigonal NaNbO3, occurs in the Jacupiranga carbonatite, in Cajati County, São Paulo State, Brazil, associated with dolomite, calcite, magnetite, phlogopite, pyrite, pyrrhotite, ancylite-(Ce), tochilinite, fluorapatite, “pyrochlore”, vigezzite, and strontianite. Pauloabibite occurs as encrustations of platy crystals, up to 2 mm in size, partially intergrown with an unidentified Ca-Nb-oxide, embedded in dolomite crystals, which in this zone of the mine can reach centimeter sizes. Cleavage is perfect on {001}. Pauloabibite is transparent and displays a sub-adamantine luster; it is pinkish brown and the streak is white. The calculated density is 4.246 g/cm3. The mineral is uniaxial; n(mean)calc is 2.078. Chemical composition (n = 17, WDS, wt%) is: Na2O 16.36, MgO 0.04, CaO 1.36, MnO 0.82, FeO 0.11, SrO 0.02, BaO 0.16, SiO2 0.03, TiO2 0.86, Nb2O5 78.66, Ta2O5 0.34, total 98.76. The empirical formula is (Na0.88Ca0.04Mn2+ 0.02)SΣ0.94(Nb0.98Ti0.02)Σ1.00-O3. X-ray powder-diffraction lines (calculated pattern) [d in Å(I)(hkl)] are: 5.2066(100)(003), 4.4257(82)(101), 3.9730(45)(012), 2.9809(54) (104), 2.3718(88)(21̄3), 1.9865(28)(024), 1.8620(53)(21̄6), and 1.5383(30)(300). It is trigonal, space group: R3̄, a = 5.3287(5), c = 15.6197(17) Å, V = 384.10(7) Å3, Z = 6. The crystal structure was solved (R1 = 0.0285, wR2 = 0.0636 for 309 observed reflections). Pauloabibite is isostructural with ilmenite and is polymorphic with isolueshite (cubic) and lueshite (orthorhombic). The name is in honor of Paulo Abib Andery (1922-1976).

Raman and infrared spectroscopic characterization of beryllonite, a sodium and beryllium phosphate mineral - implications for mineral collectors

The mineral beryllonite has been characterized by the combination of Raman spectroscopy and infrared spectroscopy. SEM-EDX was used for the chemical analysis of the mineral. The intense sharp Raman band at 1011 cm(-1), was assigned to the phosphate symmetric stretching mode. Raman bands at 1046, 1053, 1068 and the low intensity bands at 1147, 1160 and 1175 cm(-1) are attributed to the phosphate antisymmetric stretching vibrations. The number of bands in the antisymmetric stretching region supports the concept of symmetry reduction of the phosphate anion in the beryllonite structure. This concept is supported by the number of bands found in the out-of-plane bending region. Multiple bands are also found in the in-plane bending region with Raman bands at 399, 418, 431 and 466 cm(-1). Strong Raman bands at 304 and 354 cm(-1) are attributed to metal oxygen vibrations. Vibrational spectroscopy served to determine the molecular structure of the mineral. The pegmatitic phosphate minerals such as beryllonite are more readily studied by Raman spectroscopy than infrared spectroscopy.

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

Abstract 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 × 30 mm × 6 mm in size, dominated by the basal pinacoid {0001}, which is bounded by various, mostly steep, rhombohedra and the hexagonal prism {112̅0}. 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)∑0.78(Mn0.54Y0.46)∑1.00Zn1.43(Ti13.02Fe3+4.98)∑18.00(Fe3+0.32Mn0.15)∑0.47 [O37.18(OH)0.82]∑38.00. It is trigonal, space group R3̅, 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).

Recent mineral discoveries in the Coronel Murta, Taquaral, and Medina pegmatite fields, northeastern Minas Gerais, Brazil

The occurrence of five rare minerals in the Eastern Brazilian Pegmatite Province, northeastern Minas Gerais, is described and discussed: bergslagite [CaBe(AsO4)(OH)] from the Manoel Fonseca mine, Coronel Murta county; herderite [CaBe(PO4)F] from the Funil mine, Medina county; lithiophosphate [Li3PO4] from the Cachoeira mine, Aracuai/Itinga counties; lithiotantite [Li(Ta,Nb)3O8] from the Murundu mine, Itinga county; and kosnarite [KZr2(PO4)3] from Mario Pinto mine, Itinga county. The host pegmatites of these minerals, with their respective main chemical and/or mineralogical features are also presented. As a consequence of such discoveries, Raman spectra for lithiotantite and lithiophosphate were made available, and crystal structure refinement for lithiotantite was performed.