Minerals

2024

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15 pages, 13694 KiB

Open AccessArticle

Karwowskiite, Ca₉(Fe²⁺_0.5□_0.5)Mg(PO₄)₇—A New Merrillite Group Mineral from Paralava of the Hatrurim Complex, Daba-Siwaqa, Jordan

by Evgeny V. Galuskin, Irina O. Galuskina, Joachim Kusz, Maria Książek, Yevgeny Vapnik and Grzegorz Zieliński

Minerals 2024, 14(8), 825; https://doi.org/10.3390/min14080825 - 14 Aug 2024

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Abstract

Crystals of karwowskiite, Ca₉Mg(Fe²⁺_0.5□_0.5)(PO₄)₇, a new mineral of the merrillite group, were found on an amygdule wall in the central part of an anorthite–tridymite–diopside paralava of the Hatrurim Complex, Daba-Siwaqa, Jordan. The [...] Read more.

Crystals of karwowskiite, Ca₉Mg(Fe²⁺_0.5□_0.5)(PO₄)₇, a new mineral of the merrillite group, were found on an amygdule wall in the central part of an anorthite–tridymite–diopside paralava of the Hatrurim Complex, Daba-Siwaqa, Jordan. The amygdule was filled with a sulfide melt, which after crystallization gave a differentiated nodule, consisting of troilite and pentlandite parts and containing tetrataenite and nickelphosphide inclusions. Karwowskiite crystals are colorless, although sometimes a greenish tint is observed. The mineral has a vitreous luster. The microhardness VHN₂₅ is 365 (12), corresponding to 4 on the Mohs hardness scale. Cleavage is not observed, and fracture is conchoidal. The calculated density is 3.085 g/cm³. Karwowskiite is uniaxial (−): ω = 1.638 (3), ε = 1.622 (3) (λ = 589 nm), and pleochroism is not observed. The composition of karwowskiite is described by the empirical formula: Ca_9.00(□_0.54Fe²⁺_0.23Mg_0.12Na_0.04 Sr_0.03 Ni_0.03K_0.01) _Σ1.00Mg_1.00(PO₄)_7.02. Karwowskiite is distinct from the known minerals of the merrillite subgroup with the general formula A₉XM[TO₃(Ø)]₇, where A = Ca, Na, Sr, and Y; X = Na, Ca, and □; M = Mg, Fe²⁺, Fe³⁺, and Mn; T = P; and Ø = O, in that the X site in it is occupied by Fe²⁺_0.5□_0.5. Karwowskiite is trigonal, space group R-3c with a = 10.3375 (2) Å, c = 37.1443 (9) Å, and V = 3437.60 (17) Å³. Karwowskiite crystallizes at temperatures lower than 1100 °C in a thin layer of secondary melt forming on the walls of amygdules and gaseous channels in paralava as a result of contact with heated gases which are by-products of the combustion process. Full article

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14 pages, 6131 KiB

Open AccessFeature PaperArticle

Eddavidite, Cu₁₂Pb₂O₁₅Br₂, a New Mineral Species, and Its Solid Solution with Murdochite, Cu₁₂Pb₂O₁₅Cl₂

by Melli Rosenblatt, Marcus J. Origlieri, Richard Graeme III, Richard Graeme IV, Douglas Graeme and Robert T. Downs

Minerals 2024, 14(3), 307; https://doi.org/10.3390/min14030307 - 15 Mar 2024

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Abstract

Eddavidite is a new mineral species (IMA2018-010) with ideal formula, Cu₁₂Pb₂O₁₅Br₂, and cubic Fm

\bar{3}

m symmetry: a = 9.2407(9) Å; V = 789.1(2) Å³; Z = 2. Eddavidite is the bromine [...] Read more.

Eddavidite is a new mineral species (IMA2018-010) with ideal formula, Cu₁₂Pb₂O₁₅Br₂, and cubic Fm

\bar{3}

m symmetry: a = 9.2407(9) Å; V = 789.1(2) Å³; Z = 2. Eddavidite is the bromine analog of murdochite, Cu₁₂Pb₂O₁₅Cl₂, with which it forms a solid solution series. The type locality is the Southwest mine, Bisbee, Cochise County, Arizona, U.S.A. Eddavidite also occurs in the Ojuela mine, Mapimí, Durango, Mexico. Eddavidite occurs as domains within mixed murdochite–eddavidite crystals. The empirical formula, normalized to 12 Cu apfu, is Cu₁₂(Pb_1.92Fe_0.06Si_0.06)(O_15.08F_0.02)-(Br_0.99Cl_0.89☐_0.12). Type locality samples contain up to 67% eddavidite component, while Ojuela mine samples contain up to 62%. Mixed eddavidite–murdochite crystals show forms {100} and {111}; the habit grades from cubic through cuboctahedral to octahedral. Mixed eddavidite–-murdochite crystals exhibit good cleavage on {111}. Eddavidite is black, opaque with submetallic luster, and visually indistinguishable from intergrown murdochite. Its Mohs hardness is 4; d_meas. = 6.33 g/cm³, d_calc. = 6.45 g/cm³. The crystal structure, refined to R = 0.0112, consists of corner-sharing square planar CuO₄ units, arranged in Cu₁₂O₂₄ metal oxide clusters, which encapsulate Br atoms. PbO₈ cubes share edges with Cu₁₂O₂₄ clusters in a continuous framework. Eddavidite incorporates bromine remaining after desiccation of paleo-seawater at its two known localities, which were both once situated along the Western Interior Seaway. Full article

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11 pages, 3335 KiB

Open AccessArticle

Désorite, Pb₂(Fe³⁺₆Zn)O₂(PO₄)₄(OH)₈, a New Phosphate Mineral Isotypic with Jamesite

by Anthony R. Kampf, Gerhard Möhn and Chi Ma

Minerals 2024, 14(2), 175; https://doi.org/10.3390/min14020175 - 6 Feb 2024

Cited by 1 | Viewed by 1359

Abstract

The new mineral désorite, Pb₂(Fe³⁺₆Zn)O₂(PO₄)₄(OH)₈, is a secondary oxidation-zone mineral discovered on the dumps of the Schöne Aussicht mine, Dernbach, Westerwaldkreis, Rhineland-Palatinate, Germany. The crystals are irregular blades up to [...] Read more.

The new mineral désorite, Pb₂(Fe³⁺₆Zn)O₂(PO₄)₄(OH)₈, is a secondary oxidation-zone mineral discovered on the dumps of the Schöne Aussicht mine, Dernbach, Westerwaldkreis, Rhineland-Palatinate, Germany. The crystals are irregular blades up to about 0.25 mm long, occurring in subparallel and radial aggregates. Désorite is brownish red. It has an orange streak, adamantine luster, brittle tenacity, splintery and curved fracture and two cleavages: {02

\bar{1}

} perfect and {001} good. It has a hardness (Mohs) of about 3 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The calculated density is 4.633 g/cm³. Optically, crystals are biaxial (+) with α = 2.00(1), β = 2.02(calc) and γ = 2.10(calc) (white light). The 2V is 54(2)° and the optical orientation is Y ~⊥{02

\bar{1}

}, X ∧ a ≈ 13°. The mineral is pleochroic: X yellow brown, Y red brown, Z red brown; X < Y ≈ Z. The empirical formula from electron microprobe analysis is Pb_1.93(Zn_0.50Fe³⁺_6.29☐_0.21)_Σ7.00(P_3.90As_0.10)_Σ4.00O₂₆H_8.28. Désorite is triclinic, space group P

\bar{1}

; the unit-cell parameters are a = 5.4389(7), b = 9.3242(13), c = 10.0927(12) Å, α = 109.024(8), β = 90.521(6), γ = 97.588(7)°, V = 478.90(11) Å³ and Z = 1. Désorite has a framework structure (R₁ = 0.0487 for 937 I > 2σI reflections) assembled from Fe³⁺O₆ octahedra and PO₄ tetrahedra, with Pb occupying cavities in the framework. The Fe³⁺O₆ octahedra in the framework occur in edge-sharing chains, edge-sharing trimers and individual octahedra, all sharing corners with each other and with PO₄ tetrahedra. Désorite is isostructural with jamesite and lulzacite. Full article

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2023

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20 pages, 30112 KiB

Open AccessArticle

Discovery of “Meteoritic” Layered Disulphides ACrS₂ (A = Na, Cu, Ag) in Terrestrial Rock

by Evgeny V. Galuskin, Irina O. Galuskina, Yevgeny Vapnik and Grzegorz Zieliński

Minerals 2023, 13(3), 381; https://doi.org/10.3390/min13030381 - 9 Mar 2023

Cited by 2 | Viewed by 3067

Abstract

For the first time, chromium disulphides, known from meteorites, such as caswellsilverite, NaCrS₂; grokhovskyite, CuCrS₂; and a potentially new mineral, AgCrS₂, as well as the products of their alteration, such as schöllhornite, Na_0.3CrS₂∙H [...] Read more.

For the first time, chromium disulphides, known from meteorites, such as caswellsilverite, NaCrS₂; grokhovskyite, CuCrS₂; and a potentially new mineral, AgCrS₂, as well as the products of their alteration, such as schöllhornite, Na_0.3CrS₂∙H₂O, and a potentially new mineral with the formula {Fe_0.3(Ba,Ca)_0.2} CrS₂·0.5H₂O, have been found in terrestrial rock. Layered chromium disulphides were found in unusual phosphide-bearing breccia of the pyrometamorphic Hatrurim Complex in the Negev Desert, Israel. The chromium disulphides belong to the central fragment of porous gehlenite paralava cementing altered host rock clasts. The empirical formula of caswellsilverite is (Na_0.77Sr_0.03Ca_0.01)_Σ0.81(Cr³⁺_0.79Cr⁴⁺_0.18V³⁺_0.01 Fe³⁺_0.01)_Σ0.99S₂·0.1H₂O, and the end-member content of NaCrS₂ is 76%. It forms single crystals in altered pyrrhotite aggregates. Grokhovskyite has the empirical formula {Cu⁺_0.84Fe³⁺_0.10Ca_0.06 Na_0.01 Sr_0.01Ba_0.01}_Σ1.03(Cr³⁺_0.94 Fe³⁺_0.05 V³⁺_0.05)_Σ1.00S₂·0.35H₂O, and the CuCrS₂ end-member content is 75–80%. A potentially new Ag-bearing chromium disulphide is characterised by the composition (Ag_0.89Cu_0.07)_Σ0.96(Cr_0.98 Fe_0.03V_0.01Ni_0.01)_Σ1.04S₂. Caswellsilverite, grokhovskyite and AgCrS₂ form in gehlenite paralava at high temperatures (near 1000 °C) and low pressure under reducing conditions. The structure of the layered chromium disulphides, MCrS₂, is characterised by the presence of hexagonal octahedral layers (CrS₂)¹⁻, between which M-sites of the monovalent cations Ag, Cu and Na set. A low-temperature alteration of the layered chromium disulphides, when schöllhornite and {Fe_0.3(Ba,Ca)_0.2}CrS₂·0.5H₂O form, is reflected in the composition and structural modification of the layer with monovalent cations, whereas the octahedral layer (CrS₂)¹⁻ remains unchanged. Full article

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2022

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16 pages, 4930 KiB

Open AccessArticle

A Natural Vanadate–Arsenate Isomorphous Series with Jeffbenite-Type Structure: New Fumarolic Minerals Udinaite, NaMg₄(VO₄)₃, and Arsenudinaite, NaMg₄(AsO₄)₃

by Igor V. Pekov, Natalia N. Koshlyakova, Natalia V. Zubkova, Dmitry I. Belakovskiy, Marina F. Vigasina, Atali A. Agakhanov, Dmitry A. Ksenofontov, Anna G. Turchkova, Sergey N. Britvin, Evgeny G. Sidorov and Dmitry Yu. Pushcharovsky

Minerals 2022, 12(7), 850; https://doi.org/10.3390/min12070850 - 1 Jul 2022

Cited by 1 | Viewed by 2006

Abstract

Two new isostructural minerals udinaite and arsenudinaite with the end-member formulae NaMg₄(VO₄)₃ and NaMg₄(AsO₄)₃, respectively, are found in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. They are associated with one another and [...] Read more.

Two new isostructural minerals udinaite and arsenudinaite with the end-member formulae NaMg₄(VO₄)₃ and NaMg₄(AsO₄)₃, respectively, are found in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. They are associated with one another and anhydrite, diopside, hematite, schäferite, berzeliite, svabite, calciojohillerite, tilasite, reznitskyite, ludwigite, rhabdoborite-group borates, forsterite, magnesioferrite, fluorapatite, pliniusite, and powellite. Both minerals occur as equant tetragonal prismatic–dipyramidal crystals up to 0.15 mm, aggregates up to 1 cm and interrupted crusts up to 2 × 2 cm². Udinaite and arsenudinaite, visually indistinguishable from one another, are transparent, beige or brownish-yellowish, with vitreous lustre. Both minerals are optically uniaxial (–); ω = 1.785/1.777 and ε = 1.830/1.820, D_calc. = 3.613/3.816 g·cm⁻³ (udinaite/arsenudinaite). The empirical formulae are: udinaite: (Na_0.55Ca_0.16)_Σ0.71(Mg_4.04Mn_0.02Fe_0.01)_Σ4.07(V_1.63As_1.05P_0.28Si_0.03S_0.01)_Σ3.00O₁₂; arsenudinaite: (Na_0.57Ca_0.13)_Σ0.70(Mg_4.01Mn_0.01Fe_0.01)_Σ4.03(As_2.07V_0.84P_0.10Si_0.01S_0.01)_Σ3.03O₁₂. Both minerals are tetragonal, I-42d, Z = 4, a = 6.8011(2)/6.8022(1), c = 19.1839(12)/19.1843(6) Å, and V = 887.35(7)/887.66(4) Å³, R₁ = 0.0287/0.0119 (udinaite/arsenudinaite). Their crystal structure consists of the helical chains of edge-sharing MgO₆ octahedra and isolated TO₄ tetrahedra, forming a heteropolyhedral pseudo-framework with Na cations located in cavities. Both minerals are isostructural to jeffbenite. Udinaite and arsenudinaite form an isomorphous series in which the contents of T constituents vary within (in apfu): V_1.6–0.1As_2.8–1.0P_0.4–0.0. Full article

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10 pages, 2216 KiB

Open AccessArticle

Lowering R3m Symmetry in Mg-Fe-Tourmalines: The Crystal Structures of Triclinic Schorl and Oxy-Dravite, and the Mineral luinaite-(OH) Discredited

by Ferdinando Bosi, Henrik Skogby, Ulf Hålenius, Marco E. Ciriotti and Stuart J. Mills

Minerals 2022, 12(4), 430; https://doi.org/10.3390/min12040430 - 31 Mar 2022

Cited by 2 | Viewed by 2476

Abstract

Discreditation of the monoclinic tourmaline mineral species luinaite-(OH), ideally (Na,▯)(Fe²⁺,Mg)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ was approved by the IMA-CNMNC (proposal 21-L) and is described. We analyzed two luinaite-( [...] Read more.

Discreditation of the monoclinic tourmaline mineral species luinaite-(OH), ideally (Na,▯)(Fe²⁺,Mg)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ was approved by the IMA-CNMNC (proposal 21-L) and is described. We analyzed two luinaite-(OH) samples: one from the type locality Cleveland tin mine, Luina, Waratah, Tasmania, Australia, and the other from Blue Mountain Saddle (Bald Hornet Claim), North Bend, King County, Washington, DC, USA. Biaxial (−) crystals representative of the studied samples were spectroscopically (Mössbauer, polarized Fourier transform infrared, optical absorption spectroscopy), chemically (nuclear microprobe analysis and electron microprobe analysis), and structurally characterized (single-crystal X-ray diffraction). Results show the occurrence of a triclinic structure for the studied luinaite-(OH) samples, which differs only in terms of a slight structural distortion from typical trigonal tourmaline structure (the topology of the structure is retained). As a result, following the IMA-CNMNC and tourmaline nomenclature rules, the triclinic luinaite-(OH) from the type locality (Australia) can be considered as the triclinic dimorph of schorl, as its chemical composition corresponds to schorl, and thus it should be referred as schorl-1A. Similarly, the triclinic sample from the USA can be considered as the triclinic dimorph of oxy-dravite, as its chemical composition corresponds to oxy-dravite, and then is referred to as oxy-dravite-1A. Full article

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12 pages, 2903 KiB

Open AccessArticle

Radvaniceite, GeS₂, a New Germanium Sulphide, from the Kateřina Mine, Radvanice near Trutnov, Czech Republic

by Jiří Sejkora, Vladimír Žáček, Radek Škoda, František Laufek and Zdeněk Dolníček

Minerals 2022, 12(2), 222; https://doi.org/10.3390/min12020222 - 9 Feb 2022

Cited by 2 | Viewed by 2643

Abstract

The new mineral radvaniceite, GeS₂, was found on the burning coal mine dump of the abandoned Kateřina coal mine at Radvanice, near Trutnov, northern Bohemia, Czech Republic. It occurs as aggregates resembling cotton tufts up to 5 mm in size; they [...] Read more.

The new mineral radvaniceite, GeS₂, was found on the burning coal mine dump of the abandoned Kateřina coal mine at Radvanice, near Trutnov, northern Bohemia, Czech Republic. It occurs as aggregates resembling cotton tufts up to 5 mm in size; they are composed of acicular crystals up to fibres about 1–5 μm thick and up to 3 mm in length. Individual fibres are distorted and partly resemble bent wires nucleated on rock fragments or on black, crumbly ash, in association with minerals of solid solutions of Bi-Sb and stangersite, herzenbergite, and greenockite. Radvaniceite was also observed as irregular grains in a range of 10–50 μm in size, forming part of earlier multicomponent aggregates upon which the above-described crystals grow. These aggregates are formed, in addition to radvaniceite, by minerals of Bi-Sb, Bi₂S₃-Sb₂S₃ and Bi₂S₃-Bi₂Se₃ solid solutions, Bi₃S₂, Bi-sulpho/seleno/tellurides, tellurium, unnamed PbGeS₃, Cd₄GeS₆, GeAsS, Sn₅Sb₃S₇, stangersite, greenockite, cadmoindite, herzenbergite, teallite, and Sn- and/or Se-bearing galena. Radvaniceite is formed under reducing conditions by direct crystallization from hot gasses (250–350 °C) containing Cl and F at a depth of 30–60 cm under the surface of a burning coal mine dump; the mine dump fire started spontaneously, and no anthropogenic material was deposited there. Acicular crystals up to fibres of radvaniceite are elastic to flexible; are white to yellowish grey in colour, with white streaks; are translucent in transmitted light; and have vitreous to adamantine lustre. Cleavage and fracture were not observed. The calculated density is 3.05 and 2.99 g·cm⁻³ for the empirical and ideal formulae, respectively. Radvaniceite is transparent under the microscope, with a very weak pleochroism (from colourless to pale greenish yellow), and has a refraction index > 1.8. Under reflected light, radvaniceite is light grey; bireflectance and pleochroism were not observed due to abundant, white to grey, internal reflections. Anisotropy in crossed polars is distinct with grey rotation tints. Reflectance values of radvaniceite in air (R_min–R_max, %) are: 15.4–18.8 at 470 nm, 16.1–20.4 at 546 nm, 16.4–20.8 at 589 nm, and 16.9–20.9 at 650 nm. The empirical formula, based on electron-microprobe analyses, is (Ge_0.99Bi_0.01)_Σ1.0₀(S_1.9₇Se_0.03)_Σ2.0₀. The ideal formula is GeS₂, which requires Ge 53.10, S 46.90, total 100 wt. %. Radvaniceite is monoclinic, Pc, a = 6.8831(12), b = 22.501(3), c = 6.8081(11) Å, β = 120.365(9)°, with V = 909.8(4) Å³ and Z = 12. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 5.7395 (100) (11-1, 110), 5.2067 (16) (021), 3.3650 (33) (111, 11-2), 2.8417 (33) (022), 2.8236 (16) (170, 17-1), 2.8134 (20) (080) and 2.6257 (19) (240, 24-2). According to X-ray powder diffraction data and Raman spectroscopy, radvaniceite is a natural analogue of synthetic monoclinic low-temperature β-GeS₂ with distorted GeS₄ tetrahedra forming four corner-sharing tetrahedral chains, which are connected by corner-sharing tetrahedra in a three-dimensional structure. We named the mineral after its type locality, Radvanice, one of the past centres of coal mining in the Czech limb of the Intra-Sudetic Basin. This mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (number 2021-052). Full article

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2021

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18 pages, 6939 KiB

Open AccessArticle

Zoisite-(Pb), a New Orthorhombic Epidote-Related Mineral from the Jakobsberg Mine, Värmland, Sweden, and Its Relationships with Hancockite

by Natale Perchiazzi, Daniela Mauro, Pietro Vignola, Federica Zaccarini and Knut Eldjarn

Minerals 2022, 12(1), 51; https://doi.org/10.3390/min12010051 - 30 Dec 2021

Cited by 2 | Viewed by 2666

Abstract

The new mineral zoisite-(Pb), ideally CaPbAl₃(SiO₄)(Si₂O₇)O(OH), was discovered in a sample from the Jakobsberg manganese-iron oxide deposit, Värmland, Sweden. Zoisite-(Pb) is found as pale pink subhedral prisms elongated on [010], up to 0.3 mm in [...] Read more.

The new mineral zoisite-(Pb), ideally CaPbAl₃(SiO₄)(Si₂O₇)O(OH), was discovered in a sample from the Jakobsberg manganese-iron oxide deposit, Värmland, Sweden. Zoisite-(Pb) is found as pale pink subhedral prisms elongated on [010], up to 0.3 mm in size, associated with calcite, celsian, diopside, grossular, hancockite, hyalophane, native lead, phlogopite, and vesuvianite. Associated feldspars show one of the highest PbO contents (~7–8 wt%) found in nature. Electron-microprobe analysis of zoisite-(Pb) point to the empirical formula (Ca_1.09Pb_0.86Mn²⁺_0.01Na_0.01)_∑1.97(Al_2.88Fe³⁺_0.10Mn³⁺_0.04)_∑3.02Si_3.00O₁₂(OH)_1.00. The eight strongest diffraction lines [d_obs, I_obs, (hkl)] are 8.63 s (101), 8.11 mw (200), 4.895 m (011), 4.210 m (211), 3.660 s (112, 311), 3.097 mw (312), 2.900 s (013), and 2.725 m (511). Zoisite-(Pb) is isostructural with zoisite and its crystal structure was refined up to R₁ = 0.0213 for 2013 reflections with F_o > 4σ(F_o). Pb shows a stereochemically active lone pair leading to a lopsided distribution of its coordinating oxygens. A full chemical and Raman characterization of zoisite-(Pb) and of the Pb-bearing epidote hancockite is reported, together with an improved crystal structural model of hancockite, refined up to R₁ = 0.0254 for 2041 reflections with F_o > 4σ(F_o). The effects of the incorporation of Pb in the crystal structure of zoisite-(Pb), hancockite, and related synthetic and natural phases are described and discussed. Full article

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19 pages, 7473 KiB

Open AccessArticle

Dioskouriite, CaCu₄Cl₆(OH)₄∙4H₂O: A New Mineral Description, Crystal Chemistry and Polytypism

by Igor V. Pekov, Natalia V. Zubkova, Andrey A. Zolotarev, Vasiliy O. Yapaskurt, Sergey V. Krivovichev, Dmitry I. Belakovskiy, Inna Lykova, Marina F. Vigasina, Anatoly V. Kasatkin, Evgeny G. Sidorov and Dmitry Yu. Pushcharovsky

Minerals 2021, 11(1), 90; https://doi.org/10.3390/min11010090 - 18 Jan 2021

Cited by 3 | Viewed by 3578

Abstract

A new mineral, dioskouriite, CaCu₄Cl₆(OH)₄∙4H₂O, represented by two polytypes, monoclinic (2M) and orthorhombic (2O), which occur together, was found in moderately hot zones of two active fumaroles, Glavnaya Tenoritovaya and Arsenatnaya, [...] Read more.

A new mineral, dioskouriite, CaCu₄Cl₆(OH)₄∙4H₂O, represented by two polytypes, monoclinic (2M) and orthorhombic (2O), which occur together, was found in moderately hot zones of two active fumaroles, Glavnaya Tenoritovaya and Arsenatnaya, at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Dioskouriite seems to be a product of the interactions involving high-temperature sublimate minerals, fumarolic gas and atmospheric water vapor at temperatures not higher than 150 °C. It is associated with avdoninite, belloite, chlorothionite, eriochalcite, sylvite, halite, carnallite, mitscherlichite, chrysothallite, sanguite, romanorlovite, feodosiyite, mellizinkalite, flinteite, kainite, gypsum, sellaite and earlier hematite, tenorite and chalcocyanite in Glavnaya Tenoritovaya and with avdoninite and earlier hematite, tenorite, fluorophlogopite, diopside, clinoenstatite, sanidine, halite, aphthitalite-group sulfates, anhydrite, pseudobrookite, powellite and baryte in Arsenatnaya. Dioskouriite forms tabular, lamellar or flattened prismatic, typically sword-like crystals up to 0.01 mm × 0.04 mm × 0.1 mm combined in groups or crusts up to 1 × 2 mm² in area. The mineral is transparent, bright green with vitreous luster. It is brittle; cleavage is distinct. The Mohs hardness is ca. 3. D_meas is 2.75(1) and D_calc is 2.765 for dioskouriite-2O and 2.820 g cm⁻³ for dioskouriite-2M. Dioskouriite-2O is optically biaxial (+), α = 1.695(4), β = 1.715(8), γ = 1.750(6) and 2V_meas. = 70(10)°. The Raman spectrum is reported. The chemical composition (wt%, electron microprobe data, H₂O calculated by total difference; dioskouriite-2O/dioskouriite-2M) is: K₂O 0.03/0.21; MgO 0.08/0.47; CaO 8.99/8.60; CuO 49.24/49.06; Cl 32.53/32.66; H₂O(calc.) 16.48/16.38; -O=Cl −7.35/−7.38; total 100/100. The empirical formulae based on 14 O + Cl apfu are: dioskouriite-2O: Ca_1.04(Cu_4.02Mg_0.01)_Σ4.03[Cl_5.96(OH)_3.90O_0.14]_Σ10∙4H₂O; dioskouriite-2M: (Ca_1.00K_0.03)_Σ4.03(Cu_4.01Mg_0.08)_Σ4.09[Cl_5.99(OH)_3.83O_0.18]_Σ10∙4H₂O. Dioskouriite-2M has the space group P2₁/c, a = 7.2792(8), b = 10.3000(7), c = 20.758(2) Å, β = 100.238(11)°, V = 1531.6(2) Å³ and Z = 4; dioskouriite-2O: P2₁2₁2₁, a = 7.3193(7), b = 10.3710(10), c = 20.560(3) Å, V = 1560.6(3) Å³ and Z = 4. The crystal structure (solved from single-crystal XRD data, R = 0.104 and 0.081 for dioskouriite-2M and -2O, respectively) is unique. The structures of both polytypes are based upon identical BAB layers parallel to (001) and composed from Cu²⁺-centered polyhedra. The core of each layer is formed by a sheet A of edge-sharing mixed-ligand octahedra centered by Cu(1), Cu(2), Cu(3), Cu(5) and Cu(6) atoms, whereas distorted Cu(4)(OH)₂Cl₃ tetragonal pyramids are attached to the A sheet on both sides, along with the Ca(OH)₂(H₂O)₄Cl₂ eight-cornered polyhedra, which provide the linkage of the two adjacent layers via long Ca−Cl bonds. The Cu(4) and Ca polyhedra form the B sheet. The difference between the 2M and 2O polytypes arises as a result of different stacking of layers along the c axis. The cation array of the layer corresponds to the capped kagomé lattice that is also observed in several other natural Cu hydroxychlorides: atacamite, clinoatacamite, bobkingite and avdoninite. The mineral is named after Dioskouri, the famous inseparable twin brothers of ancient Greek mythology, Castor and Polydeuces, the same in face but different in exercises and achievements; the name is given in allusion to the existence of two polytypes that are indistinguishable in appearance but different in symmetry, unit cell configuration and XRD pattern. Full article

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2020

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10 pages, 4055 KiB

Open AccessArticle

Kishonite, VH₂, and Oreillyite, Cr₂N, Two New Minerals from the Corundum Xenocrysts of Mt Carmel, Northern Israel

by Luca Bindi, Fernando Cámara, Sarah E. M. Gain, William L. Griffin, Jin-Xiang Huang, Martin Saunders and Vered Toledo

Minerals 2020, 10(12), 1118; https://doi.org/10.3390/min10121118 - 13 Dec 2020

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Abstract

Here, we describe two new minerals, kishonite (VH₂) and oreillyite (Cr₂N), found in xenoliths occurring in pyroclastic ejecta of small Cretaceous basaltic volcanoes exposed on Mount Carmel, Northern Israel. Kishonite was studied by single-crystal X-ray diffraction and was found [...] Read more.

Here, we describe two new minerals, kishonite (VH₂) and oreillyite (Cr₂N), found in xenoliths occurring in pyroclastic ejecta of small Cretaceous basaltic volcanoes exposed on Mount Carmel, Northern Israel. Kishonite was studied by single-crystal X-ray diffraction and was found to be cubic, space group Fm

\bar{3}

m, with a = 4.2680(10) Å, V = 77.75(3) Å³, and Z = 4. Oreillyite was studied by both single-crystal X-ray diffraction and transmission electron microscopy and was found to be trigonal, space group P

\bar{3}

1m, with a = 4.7853(5) Å, c = 4.4630(6) Å, V = 88.51 Å³, and Z = 3. The presence of such a mineralization in these xenoliths supports the idea of the presence of reduced fluids in the sublithospheric mantle influencing the transport of volatile species (e.g., C, H) from the deep Earth to the surface. The minerals and their names have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2020-023 and 2020-030a). Full article

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28 pages, 8899 KiB

Open AccessArticle

Rippite, K₂(Nb,Ti)₂(Si₄O₁₂)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia

by Victor V. Sharygin, Anna G. Doroshkevich, Yurii V. Seryotkin, Nikolai S. Karmanov, Elena V. Belogub, Tatyana N. Moroz, Elena N. Nigmatulina, Alexander P. Yelisseyev, Vitalii N. Vedenyapin and Igor N. Kupriyanov

Minerals 2020, 10(12), 1102; https://doi.org/10.3390/min10121102 - 8 Dec 2020

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Abstract

Rippite K₂(Nb,Ti)₂(Si₄O₁₂)(O,F)₂, a new K-Nb-cyclosilicate, has been discovered in calciocarbonatites from the Chuktukon massif (Chadobets upland, SW Siberian Platform, Krasnoyarsk Territory, Russia). It was found in a primary mineral assemblage, which also includes [...] Read more.

Rippite K₂(Nb,Ti)₂(Si₄O₁₂)(O,F)₂, a new K-Nb-cyclosilicate, has been discovered in calciocarbonatites from the Chuktukon massif (Chadobets upland, SW Siberian Platform, Krasnoyarsk Territory, Russia). It was found in a primary mineral assemblage, which also includes calcite, fluorcalciopyrochlore, tainiolite, fluorapatite, fluorite, Nb-rich rutile, olekminskite, K-feldspar, Fe-Mn–dolomite and quartz. Goethite, francolite (Sr-rich carbonate–fluorapatite) and psilomelane (romanèchite ± hollandite) aggregates as well as barite, monazite-(Ce), parisite-(Ce), synchysite-(Ce) and Sr-Ba-Pb-rich keno-/hydropyrochlore are related to a stage of metasomatic (hydrothermal) alteration of carbonatites. The calcite–dolomite coexistence assumes crystallization temperature near 837 °C for the primary carbonatite paragenesis. Rippite is tetragonal: P4bm, a = 8.73885(16), c = 8.1277(2) Å, V = 620.69(2) Å³, Z = 2. It is closely identical in the structure and cell parameters to synthetic K₂Nb₂(Si₄O₁₂)O₂ (or KNbSi₂O₇). Similar to synthetic phase, the mineral has nonlinear properties. Some optical and physical properties for rippite are: colorless; Mohs’ hardness—4–5; cleavage—(001) very perfect, (100) perfect to distinct; density (meas.)—3.17(2) g/cm³; density (calc.)—3.198 g/cm³; optically uniaxial (+); ω = 1.737-1.739; ε = 1.747 (589 nm). The empirical formula of the holotype rippite (mean of 120 analyses) is K₂(Nb_1.90Ti_0.09Zr_0.01)[Si₄O₁₂](O_1.78OH_0.12F_0.10). Majority of rippite prismatic crystals are weakly zoned and show Ti-poor composition K₂(Nb_1.93Ti_0.05Zr_0.02)[Si₄O₁₂](O_1.93F_0.07). Raman and IR spectroscopy, and SIMS data indicate very low H₂O content (0.09–0.23 wt %). Some grains may contain an outermost zone, which is enriched in Ti (+Zr) and F, up to K₂(Nb_1.67Ti_0.32Zr_0.01)[Si₄O₁₂](O_1.67F_0.33). It strongly suggests the incorporation of (Ti,Zr) and F in the structure of rippite via the isomorphism Nb⁵⁺ + O²⁻ → (Ti,Zr)⁴⁺ + F¹⁻. The content of a hypothetical end-member K₂Ti₂[Si₄O₁₂]F₂ may be up to 17 mol. %. Rippite represents a new structural type among [Si₄O₁₂]-cyclosilicates because of specific type of connection of the octahedral chains and [Si₄O₁₂]⁸⁻ rings. In structural and chemical aspects it seems to be in close with the labuntsovite-supergroup minerals, namely with vuoriyarvite-(K), K₂(Nb,Ti)₂(Si₄O₁₂)(O,OH)₂∙4H₂O. Full article

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15 pages, 3974 KiB

Open AccessArticle

Rüdlingerite, Mn²⁺₂V⁵⁺As⁵⁺O₇·2H₂O, a New Species Isostructural with Fianelite

by Philippe Roth, Nicolas Meisser, Fabrizio Nestola, Radek Škoda, Fernando Cámara, Ferdinando Bosi, Marco E. Ciriotti, Ulf Hålenius, Cédric Schnyder and Roberto Bracco

Minerals 2020, 10(11), 960; https://doi.org/10.3390/min10110960 - 27 Oct 2020

Cited by 1 | Viewed by 3982

Abstract

The new mineral species rüdlingerite, ideally Mn²⁺₂V⁵⁺As⁵⁺O₇·2H₂O, occurs in the Fianel mine, in Val Ferrera, Grisons, Switzerland, a small Alpine metamorphic Mn deposit. It is associated with ansermetite and Fe oxyhydroxide in [...] Read more.

The new mineral species rüdlingerite, ideally Mn²⁺₂V⁵⁺As⁵⁺O₇·2H₂O, occurs in the Fianel mine, in Val Ferrera, Grisons, Switzerland, a small Alpine metamorphic Mn deposit. It is associated with ansermetite and Fe oxyhydroxide in thin fractures in Triassic dolomitic marbles. Rüdlingerite was also found in specimens recovered from the dump of the Valletta mine, Canosio, Cuneo, Piedmont, Italy, where it occurs together with massive braccoite and several other As- and V-rich phases in richly mineralized veins crossing the quartz-hematite ore. The new mineral displays at both localities yellow to orange, flattened elongated prismatic, euhedral crystals measuring up to 300 μm in length. Electron-microprobe analysis of rüdlingerite from Fianel gave (in wt%): MnO 36.84, FeO 0.06, As₂O₅, 25.32, V₂O₅ 28.05, SiO₂ 0.13, H₂O_calc 9.51, total 99.91. On the basis of 9 O anions per formula unit, the chemical formula of rüdlingerite is Mn_1.97(V⁵⁺_1.17 As_0.83Si_0.01)_Σ2.01O₇·2H₂O. The main diffraction lines are [d_obs in Å (I_obs) hkl]: 3.048 (100) 022, 5.34 (80) 120, 2.730 (60) 231, 2.206 (60) 16-1, 7.28 (50) 020, 2.344 (50) 250, 6.88 (40) 110, and 2.452 (40) 320. Study of the crystal structure showcases a monoclinic unit cell, space group P2₁/n, with a = 7.8289(2) Å, b = 14.5673(4) Å, c = 6.7011(2) Å, β = 93.773(2)°, V = 762.58(4) Å³, Z = 4. The crystal structure has been solved and refined to R₁ = 0.041 on the basis of 3784 reflections with F_o > 4σ(F). It shows Mn²⁺ hosted in chains of octahedra that are subparallel to [-101] and bound together by pairs of tetrahedra hosted by V⁵⁺ and As⁵⁺, building up a framework. Additional linkage is provided by hydrogen-bonding through H₂O coordinating Mn²⁺ at the octahedra. One tetrahedrally coordinated site is dominated by V⁵⁺, ^T⁽¹⁾(V_0.88As_0.12), corresponding to an observed site scattering of 24.20 electrons per site (eps), whereas the second site is strongly dominated by As⁵⁺,^T⁽²⁾(As_0.74V_0.26), with, accordingly, a higher observed site scattering of 30.40 eps. The new mineral has been approved by the IMA-CNMNC and named for Gottfried Rüdlinger (born 1919), a pioneer in the 1960–1980s, in the search and study of the small minerals from the Alpine manganese mineral deposits of Grisons. Full article

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11 pages, 1261 KiB

Open AccessArticle

Chromium Members of the Pumpellyite Group: Shuiskite-(Cr), Ca₂CrCr₂[SiO₄][Si₂O₆(OH)](OH)₂O, a New Mineral, and Shuiskite-(Mg), a New Species Name for Shuiskite

by Inna Lykova, Dmitry Varlamov, Nikita Chukanov, Igor Pekov, Dmitry Belakovskiy, Oleg Ivanov, Natalia Zubkova and Sergey Britvin

Minerals 2020, 10(5), 390; https://doi.org/10.3390/min10050390 - 26 Apr 2020

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Abstract

A new pumpellyite-group mineral shuiskite-(Cr), ideally Ca₂CrCr₂[SiO₄][Si₂O₆(OH)](OH)₂O, was found at the Rudnaya mine, Glavnoe Saranovskoe deposit, Middle Urals, Russia. It occurs on the walls of 0.5 to 1 cm thick fractures [...] Read more.

A new pumpellyite-group mineral shuiskite-(Cr), ideally Ca₂CrCr₂[SiO₄][Si₂O₆(OH)](OH)₂O, was found at the Rudnaya mine, Glavnoe Saranovskoe deposit, Middle Urals, Russia. It occurs on the walls of 0.5 to 1 cm thick fractures in chromitite, filled with calcite, Cr-bearing clinochlore, and uvarovite. Shuiskite-(Cr) forms long prismatic to acicular crystals up to 0.1 × 0.5 × 7 mm elongated along [010] and slightly flattened on [100]. The crystals are commonly combined into radial, sheaf-like aggregates. Most observed crystals are simple twins with a (001) composition plane. Shuiskite-(Cr) is greenish-black under daylight or purplish-black under incandescent light. It is optically biaxial (–), α = 1.757(5), β = 1.788(6), γ = 1.794(6), 2V (meas.) = 45(10)°, 2V (calc.) = 46° (589 nm). The D_calc is 3.432 g/cm³. The IR spectrum is reported. The chemical composition (wt.%) is CaO 21.33, MgO 3.17, Al₂O₃ 5.41, Cr₂O₃ 28.50, TiO₂ 0.18, SiO₂ 33.86, H₂O 5.82, total 98.27. The empirical formula calculated based on the sum of eight metal cations and Si atoms per formula unit is Ca_2.02Mg_0.42Cr³⁺_1.99Al_0.56Ti_0.01Si_3.00O_10.57(OH)_3.43. The simplified formula is Ca₂(Cr,Mg)(Cr,Al)₂[SiO₄][Si₂O₆(OH,O)](OH,O)(OH)₂. Shuiskite-(Cr) is monoclinic, C2/m, a = 19.2436(6), b = 5.9999(2), c = 8.8316(3) Å, β = 97.833(3)°, V = 1010.17(6) Å³, and Z = 4. The crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0469), is based on a pair of chains of edge-sharing Cr-centred octahedra running along the b axis, linked together via the [SiO₄] and [Si₂O₆(OH)] groups and Ca-centred polyhedra. The mineral species shuiskite, ideally Ca₂MgCr₂[SiO₄][Si₂O₆(OH)](OH)₃, was renamed to shuiskite-(Mg) by the decision of the IMA CNMNC. The shuiskite solid solution series with the general formula Ca₂XCr₂[SiO₄][Si₂O₆(OH,O)](OH)₂(OH,O), which includes shuiskite-(Mg) and shuiskite-(Cr) with X = Mg and Cr³⁺, respectively, appeared in the pumpellyite group. Full article

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14 pages, 3149 KiB

Open AccessArticle

Kesebolite-(Ce), CeCa₂Mn(AsO₄)[SiO₃]₃, a New REE-Bearing Arsenosilicate Mineral from the Kesebol Mine, Åmål, Västra Götaland, Sweden

by Dan Holtstam, Luca Bindi, Andreas Karlsson, Jörgen Langhof, Thomas Zack, Paola Bonazzi and Anders Persson

Minerals 2020, 10(4), 385; https://doi.org/10.3390/min10040385 - 24 Apr 2020

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Abstract

Kesebolite-(Ce), ideal formula CeCa₂Mn(AsO₄)[SiO₃]₃, is a new mineral (IMA No. 2019-097) recovered from mine dumps at the Kesebol Mn-(Fe-Cu) deposit in Västra Götaland, Sweden. It occurs with rhodonite, baryte, quartz, calcite, talc, andradite, rhodochrosite, K-feldspar, [...] Read more.

Kesebolite-(Ce), ideal formula CeCa₂Mn(AsO₄)[SiO₃]₃, is a new mineral (IMA No. 2019-097) recovered from mine dumps at the Kesebol Mn-(Fe-Cu) deposit in Västra Götaland, Sweden. It occurs with rhodonite, baryte, quartz, calcite, talc, andradite, rhodochrosite, K-feldspar, hematite, gasparite-(Ce), chernovite-(Y) and ferriakasakaite-(Ce). It forms mostly euhedral crystals, with lengthwise striation. The mineral is dark grayish-brown to brown, translucent, with light brown streak. It is optically biaxial (+), with weak pleochroism, and n_calc = 1.74. H = 5–6 and VHN₁₀₀ = 825. Fair cleavage is observed on {100}. The calculated density is 3.998(5) g·cm⁻³. Kesebolite-(Ce) is monoclinic, P2₁/c, with unit-cell parameters from X-ray single-crystal diffraction data: a = 6.7382(3), b = 13.0368(6), c = 12.0958(6) Å, β = 98.578(2)°, and V = 1050.66(9) Å³, with Z = 4. Strongest Bragg peaks in the X-ray powder pattern are: [I(%), d(Å) (hkl)] 100, 3.114 (20-2); 92, 2.924 (140); 84, 3.138 (041); 72, 2.908 (014); 57, 3.228 (210); 48, 2.856 (042); 48, 3.002 (132). The unique crystal structure was solved and refined to R1 = 4.6%. It consists of 6-periodic single silicate chains along (001); these are interconnected to infinite (010) strings of alternating, corner-sharing MnO₆ and AsO₄ polyhedra, altogether forming a trellis-like framework parallel to (100). Full article

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11 pages, 2246 KiB

Open AccessArticle

Fluorluanshiweiite, KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China

by Kai Qu, Xianzhang Sima, Guowu Li, Guang Fan, Ganfu Shen, Xing Liu, Zhibin Xiao, Hu Guo, Linfei Qiu and Yanjuan Wang

Minerals 2020, 10(2), 93; https://doi.org/10.3390/min10020093 - 21 Jan 2020

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Abstract

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite [...] Read more.

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the A site of luanshiweiite or the K-dominant analogue at the I site of voloshinite. It appears mostly in cookeite as a flaky residue, replaced by Cs-rich mica, or in the form of scale aggregates. Most individual grains are <1 mm in size, with the largest being ca. 1 cm, and the periphery is replaced by cookeite. No twinning is observed. The mineral is silvery white as a hand specimen, and in a thin section, it appears grayish-white to colorless, transparent with white streaks, with vitreous luster and pearliness on cleavage faces. It is flexible with micaceous fracture; the Mohs hardness is approximately 3; the cleavage is perfect on {001}; and no parting is observed. The measured and calculated densities are 2.94(3) and 2.898 g/cm³, respectively. Optically, fluorluanshiweiite is biaxial (–), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2V(meas.) = 25° to 35°, 2V(calc.) = 30.05°. The calculated compatibility index based on the empirical formula is −0.014 (superior). An electron microprobe analysis yields the empirical formula calculated based on 10 O atoms and 2 additional anions of (K_0.85Rb_0.12Cs_0.02Na_0.03)_Σ1.02[Li_1.05Al_1.44(□_0.47Fe_0.01Mn_0.02)_Σ0.5] _Σ2.99(Si_3.55Al_0.45) _Σ4O₁₀F₂, which can be simplified to KLiAl_1.5□_0.5(Si_3.5Al_0.5)O₁₀F₂. Fluorluanshiweiite is monoclinic with the space group C2/m and unit cell parameters a = 5.2030(5), b = 8.9894(6), c = 10.1253(9) Å, β = 100.68(1)°, and V = 465.37(7) Å³. The strongest eight lines in the X-ray diffraction data are [d in Å(I)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (112), 3.350(60) (022), 3.091(46) (112), 2.586(100) (130), and 1.506(45) (312). Full article

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2019

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11 pages, 5242 KiB

Open AccessArticle

Crystal-Chemistry of Sulfates from the Apuan Alps (Tuscany, Italy). VII. Magnanelliite, K₃Fe³⁺₂(SO₄)₄ (OH)(H₂O)₂, a New Sulfate from the Monte Arsiccio Mine

by Cristian Biagioni, Luca Bindi and Anthony R. Kampf

Minerals 2019, 9(12), 779; https://doi.org/10.3390/min9120779 - 12 Dec 2019

Cited by 8 | Viewed by 4315

Abstract

The new mineral species magnanelliite, K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as steeply terminated prisms, up to 0.5 mm in length, yellow [...] Read more.

The new mineral species magnanelliite, K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as steeply terminated prisms, up to 0.5 mm in length, yellow to orange-yellow in color, with a vitreous luster. Streak is pale yellow, Mohs hardness is ca. 3, and cleavage is good on {010}, fair on {100}. The measured density is 2.82(3) g/cm³. Magnanelliite is optically biaxial (+), with α = 1.628(2), β = 1.637(2), γ = 1.665(2) (white light), 2V_meas = 60(2)°, and 2V_calc = 59.9°. It exhibits a strong dispersion, r > v. The optical orientation is Y = b, X ^ c ~ 25° in the obtuse angle β. It is pleochroic, with X = orange yellow, Y and Z = yellow. Magnanelliite is associated with alum-(K), giacovazzoite, gypsum, jarosite, krausite, melanterite, and scordariite. Electron microprobe analyses give (wt.%): SO₃ 47.82, TiO₂ 0.05, Al₂O₃ 0.40, Fe₂O₃ 25.21, MgO 0.07, Na₂O 0.20, K₂O 21.35, H₂O_calc 6.85, total 101.95. On the basis of 19 anions per formula unit, assuming the occurrence of one (OH)⁻ and two H₂O groups, the empirical chemical formula of magnanelliite is (K_2.98Na_0.04)_Σ3.02(Fe³⁺_2.08Al_0.05Mg_0.01)_Σ2.14S_3.93O₁₆(OH)(H₂O)₂. The ideal end-member formula can be written as K₃Fe³⁺₂(SO₄)₄(OH)(H₂O)₂. Magnanelliite is monoclinic, space group C2/c, with a = 7.5491(3), b = 16.8652(6), c = 12.1574(4) Å, β = 94.064(1)°, V = 1543.95(10) Å³, Z = 4. Strongest diffraction lines of the observed X-ray powder pattern are [d(in Å), estimated visual intensity, hkl]: 6.9, medium, 021 and 110; 4.91, medium-weak, 022; 3.612, medium-weak,

\bar{1}

32, 023, and

\bar{1}

13; 3.085, strong, 202, 150, and

\bar{1}

33; 3.006, medium, 004,

\bar{1}

51, and 151; 2.704, medium, 152 and

\bar{2}

23; 2.597, medium-weak,

\bar{2}

42; 2.410, medium-weak, 153. The crystal structure of magnanelliite has been refined using X-ray single-crystal data to a final R₁ = 0.025, on the basis of 2411 reflections with F_o > 4σ(F_o) and 144 refined parameters. The crystal structure is isotypic with that of alcaparrosaite, K₃Ti⁴⁺Fe³⁺(SO)₄O(H₂O)₂. Full article

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17 pages, 4035 KiB

Open AccessFeature PaperArticle

A New Mineral Ferrisanidine, K[Fe³⁺Si₃O₈], the First Natural Feldspar with Species-Defining Iron

by Nadezhda V. Shchipalkina, Igor V. Pekov, Sergey N. Britvin, Natalia N. Koshlyakova, Marina F. Vigasina and Evgeny G. Sidorov

Minerals 2019, 9(12), 770; https://doi.org/10.3390/min9120770 - 11 Dec 2019

Cited by 8 | Viewed by 5980

Abstract

Ferrisanidine, K[Fe³⁺Si₃O₈], the first natural feldspar with species-defining iron, is an analogue of sanidine bearing Fe³⁺ instead of Al. It was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the [...] Read more.

Ferrisanidine, K[Fe³⁺Si₃O₈], the first natural feldspar with species-defining iron, is an analogue of sanidine bearing Fe³⁺ instead of Al. It was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Fissure Tolbachik Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. The associated minerals are aegirine, cassiterite, hematite, sylvite, halite, johillerite, arsmirandite, axelite, aphthitalite. Ferrisanidine forms porous crusts composed by cavernous short prismatic crystals or irregular grains up to 10 μm × 20 μm. Ferrisanidine is transparent, colorless to white, the lustre is vitreous. D_calc is 2.722 g·cm⁻³. The chemical composition of ferrisanidine (wt. %, electron microprobe) is: Na₂O 0.25, K₂O 15.15, Al₂O₃ 0.27, Fe₂O₃ 24.92, SiO₂ 60.50, in total 101.09. The empirical formula calculated based on 8 O apfu is (K_0.97Na_0.03)_Ʃ1.00(Si_3.03Fe³⁺_0.94Al_0.02)_Ʃ3.99O₈. The crystal structure of ferrisanidine was studied using the Rietveld method, the final R indices are: R_p = 0.0053, R_wp = 0.0075, R₁ = 0.0536. Parameters of the monoclinic unit cell are: a = 8.678(4), b = 13.144(8), c = 7.337(5) Å, β = 116.39(8)°, V = 749.6(9) Å³. Space group is C2/m. The crystal structure of ferrisanidine is based on the sanidine-type “ferrisilicate” framework formed by disordered [SiO₄] and [Fe³⁺O₄] tetrahedra. Full article

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13 pages, 2383 KiB

Open AccessArticle

Crystal Chemistry of Sulfates from the Apuan Alps (Tuscany, Italy). V. Scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁: A New Metavoltine-Related Mineral

by Cristian Biagioni, Luca Bindi, Daniela Mauro and Ulf Hålenius

Minerals 2019, 9(11), 702; https://doi.org/10.3390/min9110702 - 13 Nov 2019

Cited by 10 | Viewed by 4932

Abstract

The new mineral species scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs [...] Read more.

The new mineral species scordariite, K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁, was discovered in the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as pseudo-hexagonal tabular crystals, yellowish to brownish in color, up to 0.5 mm in size. Cleavage is perfect on {0001}. It is associated with giacovazzoite, krausite, gypsum, jarosite, alum-(K), and magnanelliite. Electron microprobe analyses give (wt %): SO₃ 47.31, Al₂O₃ 0.66, Fe₂O₃ 24.68, FeO 0.69, Na₂O 0.52, K₂O 17.36, H₂O_calc 15.06, total 106.28. The partitioning of Fe between Fe²⁺ and Fe³⁺ was based on Mössbauer spectroscopy. On the basis of 67 O atoms per formula unit, the empirical chemical formula is (K_7.50Na_0.34)_Σ7.84(Fe³⁺_6.29Al_0.26Fe²⁺_0.20)_Σ6.75S_12.02O₅₀·17H₂O. The ideal end-member formula can be written as K₈(Fe³⁺_0.67□_0.33)[Fe³⁺₃O(SO₄)₆(H₂O)₃]₂(H₂O)₁₁. Scordariite is trigonal, space group R-3, with (hexagonal setting) a = 9.7583(12), c = 53.687(7) Å, V = 4427.4(12) Å³, Z = 3. The main diffraction lines of the observed X-ray powder pattern are [d(in Å), estimated visual intensity]: 8.3, strong; 6.6, medium; 3.777, medium; 3.299, medium; 3.189, medium; 2.884, strong. The crystal structure of scordariite has been refined using X-ray single-crystal data to a final R₁ = 0.057 on the basis of 1980 reflections with F_o > 4σ(F_o) and 165 refined parameters. It can be described as a layered structure formed by three kinds of layers. As with other metavoltine-related minerals, scordariite is characterized by the occurrence of the [Fe³⁺₃O(SO₄)₆(H₂O)₃]⁵⁻ heteropolyhedral cluster. Full article

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15 pages, 3176 KiB

Open AccessArticle

Manganiakasakaite-(La) and Ferriakasakaite-(Ce), Two New Epidote Supergroup Minerals from Piedmont, Italy

by Cristian Biagioni, Paola Bonazzi, Marco Pasero, Federica Zaccarini, Corrado Balestra, Roberto Bracco and Marco E. Ciriotti

Minerals 2019, 9(6), 353; https://doi.org/10.3390/min9060353 - 9 Jun 2019

Cited by 6 | Viewed by 4982

Abstract

Two new monoclinic (P2₁/m) epidote supergroup minerals manganiakasakaite-(La) and ferriakasakaite-(Ce) were found in the small Mn ore deposit of Monte Maniglia, Bellino, Varaita Valley, Cuneo Province, Piedmont, Italy. Manganiakasakaite-(La) occurs as subhedral grains embedded in pyroxmangite. Its [...] Read more.

Two new monoclinic (P2₁/m) epidote supergroup minerals manganiakasakaite-(La) and ferriakasakaite-(Ce) were found in the small Mn ore deposit of Monte Maniglia, Bellino, Varaita Valley, Cuneo Province, Piedmont, Italy. Manganiakasakaite-(La) occurs as subhedral grains embedded in pyroxmangite. Its empirical formula is ^A⁽¹⁾(Ca_0.62Mn²⁺_0.38) ^A⁽²⁾(La_0.52Nd_0.08Pr_0.07Ce_0.07Y_0.01Ca_0.25) ^M⁽¹⁾(Mn³⁺_0.52Fe³⁺_0.28Al_0.18V³⁺_0.01) ^M⁽²⁾Al_1.00 ^M⁽³⁾(Mn²⁺_0.60Mn³⁺_0.27Mg_0.13) ^T⁽¹⁻³⁾(Si_2.99Al_0.01) O₁₂ (OH), corresponding to the end-member formula CaLaMn³⁺AlMn²⁺(Si₂O₇)(SiO₄)O(OH). Unit-cell parameters are a = 8.9057(10), b = 5.7294(6), c = 10.1134(11) Å, β = 113.713(5)°, V = 472.46(9) Å³, Z = 2. The crystal structure of manganiakasakaite-(La) was refined to a final R₁ = 0.0262 for 2119 reflections with F_o > 4σ(F_o) and 125 refined parameters. Ferriakasakaite-(Ce) occurs as small homogeneous domains within strongly inhomogeneous prismatic crystals, where other epidote supergroup minerals coexist [manganiandrosite-(Ce), “androsite-(Ce)”, and epidote]. Associated minerals are calcite and hematite. Its empirical formula is ^A⁽¹⁾(Ca_0.64Mn²⁺_0.36) ^A⁽²⁾(Ce_0.37La_0.17Nd_0.06Pr_0.03Ca_0.35□_0.02) ^M⁽¹⁾(Fe³⁺_0.61Al_0.39) ^M⁽²⁾Al_1.00 ^M⁽³⁾(Mn²⁺_0.64Mn³⁺_0.33Fe³⁺_0.02Mg_0.01) ^T⁽¹⁻³⁾Si_3.01 O₁₂ (OH), the end-member formula being CaCeFe³⁺AlMn²⁺(Si₂O₇)(SiO₄)O(OH). Unit-cell parameters are a = 8.9033(3), b = 5.7066(2), c = 10.1363(3) Å, β = 114.222(2)°, V = 469.66(3) Å³, Z = 2. The crystal structure of ferriakasakaite-(Ce) was refined to a final R₁ = 0.0196 for 1960 unique reflections with F_o > 4σ(F_o) and 124 refined parameters. Full article

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13 pages, 3596 KiB

Open AccessFeature PaperArticle

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece

by Federica Zaccarini, Luca Bindi, Elena Ifandi, Tassos Grammatikopoulos, Chris Stanley, Giorgio Garuti and Daniela Mauro

Minerals 2019, 9(4), 248; https://doi.org/10.3390/min9040248 - 24 Apr 2019

Cited by 11 | Viewed by 6536

Abstract

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), is a new phosphide discovered in a mantle-hosted podiform chromitite collected in the abandoned mine of Agios Stefanos (Othrys ophiolite), Central Greece. It forms tiny grains (from a few μm up [...] Read more.

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), is a new phosphide discovered in a mantle-hosted podiform chromitite collected in the abandoned mine of Agios Stefanos (Othrys ophiolite), Central Greece. It forms tiny grains (from a few μm up to about 80 μm) and occurs as isolated grains or associated with other known minerals such as nickelphosphide and awaruite, and with undetermined minerals such as Ni-allabogdanite or Ni-barringerite and a V-sulphide. Tsikourasite is brittle and has a metallic luster. In plane-polarized light, tsikourasite is white yellow and it shows no bireflectance, anisotropism or pleochroism. Internal reflections were not observed, Reflectance values of tsikourasite in air (R in %) are: 55.7 at 470 nm, 56.8 at 546 nm, 57.5 at 589 nm and 58.5 at 650 nm. Five spot analyses of tsikourasite give the average composition: P 7.97, S 0.67, V 14.13, Fe 14.37, Co 7.59, Ni 23.9, and Mo 44.16, total 99.60 wt.%, corresponding to the empirical formula (Mo_1.778V_1.071Fe_0.082Co_0.069)_Σ3.000(Ni_1.572Co_0.428)_Σ2.000(P_0.981S_0.079)_Σ1.060, on the basis of Σ(Mo +V + Fe + Co + Ni) = 5 apfu and taking into account the structural results. The simplified formula is Mo₃Ni₂P_1+x (x < 0.25). The density, which was calculated based on the empirical formula and single-crystal data, is 9.182 g/cm³. The mineral is cubic, space group F-43m, with a = 10.8215(5) Å and Z = 16. Although tsikourasite is similar in composition to those of monipite (MoNiP), polekhovskyite (MoNiP₂), and the synthetic compound MoNiP₂, all these phases are hexagonal and not cubic like tsikourasite. It exhibits the same structure as the cubic Mo₃Ni₂P_1.18 compound [space group F-43m, a = 10.846(2) Å] synthesized at 1350 °C. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2018-156). The mineral honors Professor Basilios Tsikouras of the Universiti Brunei Darussalam. Full article

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8 pages, 1022 KiB

Open AccessArticle

Spiridonovite, (Cu_1-xAg_x)₂Te (x ≈ 0.4), a New Telluride from the Good Hope Mine, Vulcan, Colorado (U.S.A.)

by Marta Morana and Luca Bindi

Minerals 2019, 9(3), 194; https://doi.org/10.3390/min9030194 - 24 Mar 2019

Cited by 1 | Viewed by 4415

Abstract

Here we describe a new mineral in the Cu-Ag-Te system, spiridonovite. The specimen was discovered in a fragment from the cameronite [ideally, Cu_5-x(Cu,Ag)_3+xTe₁₀] holotype material from the Good Hope mine, Vulcan, Colorado (U.S.A.). It occurs as black [...] Read more.

Here we describe a new mineral in the Cu-Ag-Te system, spiridonovite. The specimen was discovered in a fragment from the cameronite [ideally, Cu_5-x(Cu,Ag)_3+xTe₁₀] holotype material from the Good Hope mine, Vulcan, Colorado (U.S.A.). It occurs as black grains of subhedral to anhedral morphology, with a maximum size up to 65 μm, and shows black streaks. No cleavage is observed and the Vickers hardness (VHN₁₀₀) is 158 kg·mm⁻². Reflectance percentages in air for R_min and R_max are 38.1, 38.9 (471.1 nm), 36.5, 37.3 (548.3 nm), 35.8, 36.5 (586.6 nm), 34.7, 35.4 (652.3 nm). Spiridonovite has formula (Cu_1.24Ag_0.75)_Σ1.99Te_1.01, ideally (Cu_1-xAg_x)₂Te (x ≈ 0.4). The mineral is trigonal and belongs to the space group P-3c1, with the following unit-cell parameters: a = 4.630(2) Å, c = 22.551(9) Å, V = 418.7(4) Å ³, and Z = 6. The crystal structure has been solved and refined to R1 = 0.0256. It can be described as a rhombohedrally-compressed antifluorite structure, with a rough ccp arrangement of Te atoms. It consists of two Te sites and three M (metal) sites, occupied by Cu and Ag, and is characterized by the presence of edge-sharing tetrahedra, where the four-fold coordinated M atoms lie. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2018-136). Full article

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