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Kampf A.R.,Natural History Museum of Los Angeles County | Camara F.,University of Turin | Ciriotti M.E.,Associazione Micromineralogica Italiana | Nash B.P.,University of Utah | Balestra C.,Associazione Micromineralogica Italiana
European Journal of Mineralogy | Year: 2016

Castellaroite (IMA2015-071), Mn2+ 3 (AsO4)24.5H2O, is a new secondary arsenate mineral from the Monte Nero mine, Rocchetta Vara, La Spezia, Liguria, Italy and the Valletta mine, near Canosio, Cuneo, Piedmont, Italy. It crystallized from As-and Mn-rich hydrothermal fluids in an oxidizing environment. At Monte Nero, it is associated with coralloite, manganohörnesite, rhodochrosite, sarkinite, sterlinghillite, strashimirite and wallkilldellite. At Valletta, it is associated with braccoite, hematite, manganberzeliite, orthoclase and tiragalloite. Castellaroite occurs as thin blades, flattened on [001], striated and elongated parallel to [100] and exhibiting the forms {110}, {012} and {001}. The mineral is colourless and transparent with a vitreous to silky lustre and white streak. Crystals are flexible with a curved fracture, and one perfect cleavage on {001}. The Mohs' hardness is 2=. The measured and calculated densities are 3.14(2) gcm-3 and 3.164 gcm-3, respectively. The mineral is easily soluble in dilute HCl at room temperature. Optically, castellaroite crystals are biaxial (-), with α = 1.644(1), β = 1.662(1) and γ = 1.667(1) (white light); 2V = 57(1)°; dispersion r < v, moderate; the optical orientation Y = b; Z ≈ a. The Raman spectrum is dominated by features corresponding to the AsO4 group and also confirms the presence of H2O. Electron-microprobe analyses gave the empirical formula Mn2+ 3.02(As1.94P0.06)σ2.00O12.5H8.96, based on 12.5 O apfu. Castellaroite is monoclinic, P21/n, with the unit-cell parameters: A = 8.7565(8), b = 13.4683(13), c = 18.652(2) A, β = 94.876(7)°, V = 2191.7(4) A3 and Z = 8. The eight strongest lines in the X-ray powder diffraction pattern are [dobs/A (I) (hkl)]: 10.90(100)(011), 9.27(67)(002), 6.97(42)(111), 3.323(47)(multiple), 3.043(87) (134,204,232), 2.656(85)(multiple), 2.165(46)(multiple), and 1.5589(32)(multiple). The crystal structure was refined to R1 = 0.118 for 2513 observed reflections [Fo > 4δF]. The structure contains kinked chains of edge-sharing MnO6 octahedra parallel to [100]. The chains are linked to each other by corner-sharing, forming sheets parallel to {001} and AsO4 tetrahedra corner-link with octahedra in the sheet, forming a heteropolyhedral layer. Edge-sharing MnO6-MnO5 dimers share corners with octahedra and tetrahedra in adjacent layers, thereby linking them in the [001] direction. The heteropolyhedral layer is topologically identical to those in the structures of the phosphate minerals: Angarfite, bakhchisaraitsevite, mejillonesite, metaswitzerite, rimkorolgite and switzerite. Overall, the structure is most similar to that of metaswitzerite. © 2016 E. Schweizerbart'sche Verlagsbuchhandlung.

Oberti R.,CNR Institute of Geosciences and Earth Resources | Boiocchi M.,University of Pavia | Hawthorne F.C.,University of Manitoba | Camara F.,University of Turin | And 2 more authors.
Canadian Mineralogist | Year: 2015

The crystal-chemical characterization of an amphibole with an unusual composition, A(Na0.76K0.24)B(Ca1.42Na0.56Mn2+ 0.02) C(Mg2.64Fe2+ 1.95Mn2+ 0.07Mg2.64Zn0.01Fe3+ 0.01Ti4+ 0.32)T(Si7.18Al0.82)O22 W[(OH)0.58O0.27F1.15], found in pegmatitic veins at Kariasen, Larvik Plutonic Complex, Norway, provides an excellent example of the detection and estimation of the oxo component in amphibole. The use of Ti as a proxy for the oxo component is discussed and a procedure to derive accurate Ti partitioning from the results of structure refinement is described. Because the presence and amount of oxo component in amphiboles are important in order to determine values of fO2 and fH2O, especially in igneous and magmatic systems, this procedure should be applied any time the compositional data or the petrological context indicate the presence of significant Ti, or suggest that the oxo component may be a relevant issue.

Bindi L.,University of Florence | Christy A.G.,Australian National University | Mills S.J.,Khan Research Laboratories | Ciriotti M.E.,Associazione Micromineralogica Italiana | Bittarello E.,University of Turin
Canadian Mineralogist | Year: 2016

Jamborite was originally described with the formula (Ni2+,Ni3+,Fe)(OH)2(OH,S,H2O) from Ca' de' Ladri and Monteacuto Ragazza near Bologna, and Castelluccio di Moscheda near Modena, Italy. Re-examination of the mineral from the type localities and Rio Vesale, Sestola, Val Panaro (Emilia-Romagna, Italy), led to the discovery of a crystal suitable for study by single-crystal and powder X-ray diffraction, SEM-EDS, and Raman spectroscopy. Jamborite crystallizes in the space group R3m, with the unit-cell parameters a 3.068(4) Å, c 23.298(11) Å, and Z = 3. The structure refinement (R1 = 0.0818) showed that jamborite contains brucite-like sheets of edge-sharing octahedra (Ni2+,M3+)(O,OH)6 with a distinctive double layer of partially occupied H2O molecules between them. Raman data indicate that the sulfur is present as sulfate rather than sulfide. The new analytical data were recalculated on the basis of 1 (Ni+Ca+Co+Fe) to give the formula [(Ni2+ 0.902Ca2+ 0.002)(Co3+ 0.072Fe3+ 0.024)]Σ1.000 (OH)1.884Cl0.012(H2O)0.004(SO4)0.100·0.900H2O. The sulfur occupancy was too low to be located in the refinement, but the '1:1 ratio of M3+:S from the chemical analysis implies that SO4 2- replaces OH- in the brucite sheet rather than sitting in the interlayer space. The splitting of the H2O layer allows avoidance of short SO4 2-⋯H2O distances. Thus, jamborite is not a member of the hydrotalcite supergroup. Jamborite is redefined as M2+ 1-xM3+ x(OH)2-x(SO4)x·nH2O, where M2+ is dominantly Ni, M3+ is dominantly Co, x ≤ 1/3 and probably ≤ 1/7 (x =0.10 for the neotype sample), and n < (1-x). The low M3+/M2+ ratio relative to honessite and hydrohonessite and high Co content may explain the rarity of jamborite as an early alteration product of millerite. The redefinition of jamborite and designation of the neotype specimen from Rio Vesale have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC), voting proposal 14-E.

Bittarello E.,University of Turin | Camara F.,University of Turin | Ciriotti M.E.,Associazione Micromineralogica Italiana | Marengo A.,University of Turin
Mineralogy and Petrology | Year: 2015

Ottensite, Na3 (Sb2O3)(SbS3)·3H2O, brizziite, NaSbO3, and mopungite, NaSb(OH)6, have been found on several specimens from the antimony mine of Pereta (Grosseto, Tuscany, Italy). Ottensite from Pereta mine occurs as brilliant reddish-brown spheroidal aggregates, with a diameter up to 0.2 mm, formed by radially oriented individuals. These aggregates are associated with well-shaped tabular and pseudocubic colourless crystals of mopungite and platy aggregates of brizziite. This is the second world occurrence of ottensite and brizziite. The mineral species were characterized by electron microprobe analysis, X-ray diffraction study and microRaman spectroscopy. Single-crystal X-ray diffraction data were collected on a twinned crystal of mopungite and the structure was for the first time refined on a natural sample in space group P42/n [unit cell parameters a = 8.036(3) Å, c = 7.926(6) Å, V = 511.88(5) Å3, Z = 4] obtaining an R1-index of 5.17, wR2 of 13.52 and GooF of 1.247. © 2015, Springer-Verlag Wien.

Mills S.J.,Khan Research Laboratories | Bindi L.,University of Florence | Cadoni M.,University of Turin | Kampf A.R.,Natural History Museum of Los Angeles County | And 2 more authors.
European Journal of Mineralogy | Year: 2012

Paseroite, ideally PbMn2+(Mn2+,Fe2+) 2(V5+,Ti,Fe3+,□)18O38, isanewmineral(IMA2011-069) fromfossil wood in the upper part of the Molinello mine, Val Graveglia, Italy. Paseroite occurs in direct association with quartz, chalcocite, volborthite, metatyuyamunite and pyrophanite, and was also found as zones within V-rich senaite crystals with which it forms a solid-solution series. Paseroite forms as isolated submetallic, dark grey to black, elongated scalenohedral crystals between 50 and 100 mm in length, with the forms {001} and {102} present. The tenacity is brittle, the fracture conchoidal, and the streak is black. The Vickers hardness is 847 kg mm-2 (load 500g), which is equivalent to 6-6.5 on the Mohs scale. The calculated density is 4.315 g/cm3 (on the basis of the empirical formula). In plane-polarised incident light, paseroite is greyish in colour, weakly bireflectant and non-pleochroic. Internal reflections are absent. Between crossed polars, paseroite is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) are: 18.4 %, 18.2 % (471.1 nm); 17.9 %, 17.7 % (548.3 nm); 17.6 %, 17.3 % (586.6 nm); and 17.0 %, 16.8 % (652.3 nm), respectively. The empirical formula, calculated on the basis of 38 O atomspfu is: (Pb 0.61Sr0.39)Σ1.00(V5+ 7.78Ti4+7.03Mn2+ 1.86Fe2+0.67Fe3+ 0.37Zn0.24Na0.19U0.02Mg 0.0□2.82)Σ21.00O38. According to the structural results, the simplified formula is: PbMn 2+(Mn2+,Fe2+)2(V5+,Ti,Fe 3+,□)18O38. Structurally, paseroite crystallises in the space group R3, with the unit-cell parameters a = 10.3894(5), c = 20.8709(8) Å, V = 1950.98(15) Å3 and Z = 3. The crystal structure was refined to R = 0.0234 for 632 reflections with Io > 2σ(Io) and is isostructural with senaite and all other members of the crichtonite group. The eight strongest X-ray powder-diffraction lines [d in A (I/I0) (hkl)] are: 3.417 (100) (024), 3.012 (21) (300), 2.896 (61) (216), 2.858 (36) (214), 2.765 (27) (303), 2.260 (85) (144), 2.149 (65) (415) and 1.809 (57) (418). The name is after Marco Pasero (b. 1958), Professor of Mineralogy at the University of Pisa. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung.

Lepore G.O.,University of Florence | Bindi L.,University of Florence | Zanetti A.,CNR Institute of Geosciences and Earth Resources | Ciriotti M.E.,Associazione Micromineralogica Italiana | And 2 more authors.
American Mineralogist | Year: 2015

A mica-group mineral characterized by a high V content and free of Al was found in the mangane- siferous beds within the metacherts of the ophiolitic sequences at the Cerchiara mine, Eastern Liguria (Italy), in association with hematite, quartz, and calcite. Chemical and structural characterization supported by Raman data defines this phase as a new mineral species, which is named balestraite after Corrado Balestra, a prominent Italian amateur mineralogist. Balestraite, ideally KLi2V5+Si4O10O2, is a 1M trioctahedral mica crystallizing in the C2 space group, with a = 5.2024(5), b = 8.9782(7), c = 9.997(2) Å, β = 100.40(2)°, V = 459.3(1) Å3, Z = 2. The reduction of symmetry from the "ideal" space group C2/m is related to the ordering of V at only one of the two pseudo-symmetric octahedral sites. Vanadium forms very distorted octahedra with a [2+2+2] geometry characteristic of the valence state +5. The Li,V composition of the octahedral sheet, the pure tetrasilicic character of the tetrahedral sheet, and the anhydrous character produce unusual geometrical features for this mica. The occurrence of 5+ as the dominant valence state of V and the virtually complete O2- → OH- substitution at the O4 site indicate strongly oxidizing conditions of crystallization, which are consistent with balestraite occurring at the boundary between carbonate-bearing veins and hematite bands. The new mineral and name were approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2013-080). © 2015 by Walter de Gruyter Berlin/Boston 2015.

Bindi L.,University of Florence | Biagioni C.,University of Pisa | Martini B.,Associazione Micromineralogica Italiana | Salvetti A.,Associazione Micromineralogica Italiana
Minerals | Year: 2016

The new mineral species ciriottiite, ideally Cu(Cu,Ag)3Pb19(Sb,As)22(As2)S56 has been discovered in the Tavagnasco mining district, Piedmont, Italy, as very rare black metallic tubular crystals, up to 150 μm in length, associated with Bi sulfosalts and arsenopyrite. Its Vickers hardness (VHN10) is 203 kg/mm2 (range 190-219). In reflected light, ciriottiite is light grey in color, distinctly anisotropic with brownish to greenish rotation tints. Internal reflections are absent. Reflectance values for the four COM wavelengths (Rmin, Rmax (%) (λ in nm)) are: 33.2, 37.8 (471.1); 31.8, 35.3 (548.3), 31.0, 34.7 (586.6); and 27.9, 32.5 (652.3). Electron microprobe analysis gave (in wt %, average of 5 spot analyses): Cu 2.33 (8), Ag 0.53 (5), Hg 0.98 (6), Tl 0.78 (3), Pb 44.06 (14), As 4.66 (7), Sb 23.90 (10), Bi 1.75 (7), total 99.38 (26). On the basis of 56 S atoms per formula unit, the chemical formula of ciriottiite is Cu3.23(11)Ag0.43(4)Hg0.43(2)Pb18.74(9)Tl0.34(1)Sb17.30(5)As5.48(10)Bi0.74(3)S56. The main diffraction lines, corresponding to multiple hkl indices, are (d in Å (relative visual intensity)): 4.09 (m), 3.91 (m), 3.63 (vs), 3.57 (m), 3.22 (m), 2.80 (mw), 2.07 (s). The crystal structure study revealed ciriottiite to be monoclinic, space group P21/n, with unit-cell parameters a = 8.178 (2), b = 28.223 (6), c = 42.452 (5) Å, β= 93.55 (2)°, V = 9779.5 (5) Å3, Z = 4. The crystal structure was refined to a final R1 = 0.118 for 21304 observed reflections. Ciriottiite is the Cu analogue of sterryite and can be described as an expanded derivative of owyheeite. The name ciriottiite honors Marco Ernesto Ciriotti (b. 1945) for his longstanding contribution to mineral systematics. © 2016 by the authors; licensee MDPI, Basel, Switzerland.

Biagioni C.,University of Pisa | Bonaccorsi E.,University of Pisa | Bonaccorsi E.,CNR Institute of Geosciences and Earth Resources | Pasero M.,University of Pisa | And 5 more authors.
American Mineralogist | Year: 2011

Ambrinoite, ideally (K,NH4)2(As,Sb)8S 13.H2O, occurs as a rare sulfosalt species in the Triassic evaporitic formation of Gessi (gypsum) outcropping near the hamlet of Signols (Oulx, Susa Valley, Torino, Piedmont, Italy). The new species is associated with sulfur and orpiment; in the same occurrence galkhaite, stibnite, and enargite were also identified. Ambrinoite occurs as aggregates of tabular crystals up to 1 mm in length. The color is red, with an orange-red streak; the luster is vitreous to resinous. The mineral is transparent; its microhardness VHN (10 g) = 30 kg/mm2, corresponding to a Mohs hardness of about 2. Electron microprobe analysis gives the empirical formula [K 1.43(NH4)0.42Na0.02Tl 0.01]σ=1.88 (As5.82Sb2.18) σ=8.00S13.22.1.2H2O, close to stoichiometric [K1.5(NH4)0.5]σ=2(As 6Sb2)σ=8S13.H2O; the calculated density is 3.276 g/cm3. Micro-Raman spectroscopy confirmed the presence of water and ammonium cation. Ambrinoite is triclinic, space group P1̄, with a = 9.704(1), b = 11.579(1), c = 12.102(2) Å, α = 112.82(1), β = 103.44(1), γ = 90.49(1)°, V = 1211.6(3) Å3, Z = 2. The strongest X-ray powder diffraction lines [d in Å (I) (hkl)] are: 10.78 (100) (001), 5.79 (55) (021)̄, 4.23 (35) (102), 5.31 (34) (102)̄, 5.39 (32) (002). Its crystal structure has been solved by X-ray single-crystal diffraction on the basis of 2667 unique reflections, with a final R = 0.035. It is formed by two kinds of modules: Slabs (110)PbS of modified PbS archetype (type A slabs) and openwork slabs with channels accomodating (K,NH4)+ cations and H2O molecules (type B slabs). Its structure can be described as an order-disorder (OD) structure, built up by two different kinds of layers. Taking into account only the short (As,Sb)-S bonds, (As,Sb)S3 triangular pyramids form double chains similar to those described in other natural and synthetic compounds, among which its homeotype gillulyite, as well as gerstleyite. Ambrinoite belongs to the hutchinsonite merotypic family. It is probably the product of late-stage hydrothermal fluid circulation. The name of this new mineral species (IMA 2009-071) honors Pierluigi Ambrino (b. 1947), the mineral collector who kindly provided us with the studied specimens.

Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Nestola F.,University of Padua | Ciriotti M.E.,Associazione Micromineralogica Italiana | Kasaasaasatkin A.V.,V O Almazjuvelirexport
American Mineralogist | Year: 2013

Saltonseaite, K3NaMn2+Cl6, is a new mineral from the Salton Sea, Imperial County, California, U.S.A., which formed as the result of the evaporation of geothermal (hydrothermal) brines enriched in K, Na, Mn, and Cl. It occurs as lozenge-shaped and bladed crystals to about 10 cm that are composites of parallel-grown {012} rhombohedra. It is associated with large, well-formed crystals of sylvite and halite. Crystals are transparent and colorless, but appear light orange due to inclusions of akaganéite. The streak is white and the luster is vitreous to oily, the latter being due to deliquescence. The Mohs hardness is about 21/2, the tenacity is brittle, the fracture is irregular, and crystals exhibit one very good cleavage on {110}. The mineral has an astringent taste and is markedly hygroscopic. The measured and calculated densities are 2.26(1) and 2.297 g/cm3, respectively. Saltonseaite is soluble in water at room temperature and crystallizes from solution above 52 °C. Optically, saltonseaite is uniaxial positive, with ω = 1.577(1) and ε = 1.578(1) (white light) and is non-pleochroic. Energy-dispersive spectroscopic analyses (average of 5) provided: K 28.79, Na 5.35, Mn 13.48, Fe 0.24, Cl 52.19, total 100.05 wt%. The empirical formula (based on 6 Cl atoms) is: K3.00Na0.95Mn 1.002+Fe0.022+Cl6. Saltonseaite is trigonal, R3̄c, with cell parameters a = 12.0966(5), c = 13.9555(10) Å, V = 1768.48(16) Å3, and Z = 6. The nine strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 5.83(61)(012); 3.498(25)(300); 2.851(68)(131); 2.689(32)(312); 2.625(62)(214); 2.542(100)(223); 1.983(32)(324); 1.749(20)(600), and 1.384(22)(multiple). The structure of saltonseaite (R1 = 1.08% for 558 Fo > 4σF) contains face-sharing chains of alternating Mn2+Cl6 octahedra and NaCl6 polyhedra along c. The chains are joined via bonds to eight-coordinated K atoms. Saltonseaite is isostructural with rinneite, K3NaFe2+Cl6, and very similar in structure with chlormanganokalite, K4Mn 2+Cl6. Existing chemical analyses for saltonseaite and rinneite fail to confirm a solid-solution series between them; experimental studies are needed.

Ciriotti M.E.,Associazione Micromineralogica Italiana
European Journal of Mineralogy | Year: 2015

Churchite-(Nd) and iodine, up to now recognized as valid minerals by IMA CNMNC, are discredited because, for different reasons, both are non-existent mineral species and were never actually characterized. Churchite-(Nd) is in fact neodymium-rich churchite-(Y) and iodine has never been found at its sole purported type locality of Vesuvius. Both discreditations have been approved by the IMA CNMNC (15-C and 15-D). © 2015 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

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