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4 pages, 185 KiB

Open AccessEditorial

Editorial for Special Issue “New Mineral Species and Their Crystal Structures”

by Irina O. Galuskina and Igor V. Pekov

Minerals 2019, 9(2), 106; https://doi.org/10.3390/min9020106 - 13 Feb 2019

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Abstract

Mineralogy is the oldest and one of the most important sciences of the geological cycle [...] Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

Research

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10 pages, 3195 KiB

Open AccessArticle

Verneite, Na₂Ca₃Al₂F₁₄, a New Aluminum Fluoride Mineral from Icelandic and Vesuvius Fumaroles

by Tonči Balić-Žunić, Anna Garavelli, Daniela Pinto and Donatella Mitolo

Minerals 2018, 8(12), 553; https://doi.org/10.3390/min8120553 - 28 Nov 2018

Cited by 7 | Viewed by 3792

Abstract

Verneite, Na₂Ca₃Al₂F₁₄, is a new mineral first discovered in fumarolic samples from both Hekla, Iceland and Vesuvius, Italy. Additional occurrences are so far from Eldfell and Fimmvörduhals, both on Iceland. Verneite is cubic, I2₁ [...] Read more.

Verneite, Na₂Ca₃Al₂F₁₄, is a new mineral first discovered in fumarolic samples from both Hekla, Iceland and Vesuvius, Italy. Additional occurrences are so far from Eldfell and Fimmvörduhals, both on Iceland. Verneite is cubic, I2₁3, a = 10.264(1) Å, V = 1081.4(3) Å³, Z = 4, and corresponds to the known synthetic compound. The empirical formula is Na_2.01Ca_2.82Al_2.17F_14.02 (scanning electron microscopy with energy dispersive spectrometer from an unpolished sample). It appears in crystals up to 20 μm in diameter, with {110}, {100}, and {111} as the main forms. In the crystal structure of its synthetic analogue, Na is coordinated by 7 F atoms in the form of a capped octahedron, Ca with 8 F atoms in the form of a bisdisphenoid, and Al with 6 F atoms in the form of an octahedron. The crystal structure of Na₂Ca₃Al₂F₁₄ contains sinuous chains of Ca coordination polyhedra interlacing with similarly sinuous chains of Na coordination polyhedra and forming together with them layers parallel to {100}. The intersecting layers parallel to three equivalent crystallographic planes form a three-dimensional mesh with Al coordinations imbedded in its holes. The characteristics of Ca coordinations in fluorides, as well as their relations to other ternary Na–Ca–Al fluorides are discussed. Verneite is named after Jules Verne. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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18 pages, 5486 KiB

Open AccessEditor’s ChoiceArticle

Copper in Natural Oxide Spinels: The New Mineral Thermaerogenite CuAl₂O₄, Cuprospinel and Cu-Enriched Varieties of Other Spinel-Group Members from Fumaroles of the Tolbachik Volcano, Kamchatka, Russia

by Igor V. Pekov, Fedor D. Sandalov, Natalia N. Koshlyakova, Marina F. Vigasina, Yury S. Polekhovsky, Sergey N. Britvin, Evgeny G. Sidorov and Anna G. Turchkova

Minerals 2018, 8(11), 498; https://doi.org/10.3390/min8110498 - 1 Nov 2018

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Abstract

This paper is the first description of natural copper-rich oxide spinels. They were found in deposits of oxidizing-type fumaroles related to the Tolbachik volcano, Kamchatka, Russia. This mineralization is represented by nine species with the following maximum contents of CuO (wt.%, given in [...] Read more.

This paper is the first description of natural copper-rich oxide spinels. They were found in deposits of oxidizing-type fumaroles related to the Tolbachik volcano, Kamchatka, Russia. This mineralization is represented by nine species with the following maximum contents of CuO (wt.%, given in parentheses): a new mineral thermaerogenite, ideally CuAl₂O₄ (26.9), cuprospinel, ideally CuFe³⁺₂O₄ (28.6), gahnite (21.4), magnesioferrite (14.7), spinel (10.9), magnesiochromite (9.0), franklinite (7.9), chromite (5.9), and zincochromite (4.8). Cuprospinel, formerly known only as a phase of anthropogenic origin, turned out to be the Cu-richest natural spinel-type oxide [sample with the composition (Cu_0.831Zn_0.100Mg_0.043Ni_0.022)_Σ0.996(Fe³⁺_1.725Al_0.219Mn³⁺_0.048Ti_0.008)_Σ2.000O₄ from Tolbachik]. Aluminum and Fe³⁺-dominant spinels (thermaerogenite, gahnite, spinel, cuprospinel, franklinite, and magnesioferrite) were deposited directly from hot gas as volcanic sublimates. The most probable temperature interval of their crystallization is 600–800 °C. They are associated with each other and with tenorite, hematite, orthoclase, fluorophlogopite, langbeinite, calciolangbeinite, aphthitalite, anhydrite, fluoborite, sylvite, halite, pseudobrookite, urusovite, johillerite, ericlaxmanite, tilasite, etc. Cu-bearing spinels are among the latest minerals of this assemblage: they occur in cavities and overgrow even alkaline sulfates. Cu-enriched varieties of chrome-spinels (magnesiochromite, chromite, and zincochromite) were likely formed in the course of the metasomatic replacement of a magmatic chrome-spinel in micro-xenoliths of ultrabasic rock under the influence of volcanic gases. The new mineral thermaerogenite, ideally CuAl₂O₄, was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption. It forms octahedral crystals up to 0.02 mm typically combined in open-work clusters up to 1 mm across. Thermaerogenite is semitransparent to transparent, with a strong vitreous lustre. Its colour is brown, yellow-brown, red-brown, brown-yellow or brown-red. The mineral is brittle, with the conchoidal fracture, cleavage is none observed. D(calc.) is 4.87 g/cm³. The chemical composition of the holotype (wt.%, electron microprobe) is: CuO 25.01, ZnO 17.45, Al₂O₃ 39.43, Cr₂O₃ 0.27, Fe₂O₃ 17.96, total 100.12 wt.%. The empirical formula calculated on the basis of 4 O apfu is: (Cu_0.619Zn_0.422)_Σ1.041(Al_1.523Fe³⁺_0.443Cr_0.007)_Σ1.973O₄. The mineral is cubic, Fd-3m, a = 8.093(9) Å, V = 530.1(10) Å³. Thermaerogenite forms a continuous isomorphous series with gahnite. The strongest lines of the powder X-ray diffraction pattern of thermaerogenite [d, Å (I, %) (hkl)] are: 2.873 (65) (220), 2.451 (100) (311), 2.033 (10) (400), 1.660 (16) (422), 1.565 (28) (511) and 1.438 (30) (440). Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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10 pages, 2516 KiB

Open AccessArticle

Parafiniukite, Ca₂Mn₃(PO₄)₃Cl, a New Member of the Apatite Supergroup from the Szklary Pegmatite, Lower Silesia, Poland: Description and Crystal Structure

by Adam Pieczka, Cristian Biagioni, Bożena Gołębiowska, Piotr Jeleń, Marco Pasero and Maciej Sitarz

Minerals 2018, 8(11), 485; https://doi.org/10.3390/min8110485 - 26 Oct 2018

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Abstract

Parafiniukite, ideally Ca₂Mn₃(PO₄)₃Cl, is a new apatite-supergroup mineral from the Szklary pegmatite, Lower Silesia, Poland. It occurs as anhedral grains, up to 250 µm in size, dark olive green in colour, embedded in a mixture [...] Read more.

Parafiniukite, ideally Ca₂Mn₃(PO₄)₃Cl, is a new apatite-supergroup mineral from the Szklary pegmatite, Lower Silesia, Poland. It occurs as anhedral grains, up to 250 µm in size, dark olive green in colour, embedded in a mixture of Mn-oxides and smectites around beusite. It has a vitreous luster, and it is brittle with irregular, uneven fracture. The calculated density is 3.614 g·cm⁻³. Parafiniukite is hexagonal, space group P6₃/m, with unit-cell parameters a = 9.4900(6), c = 6.4777(5) Å, V = 505.22(5) Å³, Z = 2. The eight strongest reflections in the calculated X-ray powder diffraction pattern of parafiniukite are [d in Å (I) hkl]: 3.239 (39) 002; 2.801 (55) 211; 2.801 (76) 121; 2.740 (100) 300; 2.675 (50) 112; 2.544 (69) 202; 1.914 (31) 222; and 1.864 (22) 132. Chemical analysis by an electron microprobe gave (in wt%) P₂O₅ 39.20, MgO 0.19, CaO 24.14, MnO 31.19, FeO 2.95, Na₂O 0.05, F 0.39, Cl 3.13, H₂O_(calc) 0.68, O=(Cl,F) −0.87, sum 101.05. The resulting empirical formula on the basis of 13 anions per formula unit is (Mn_2.39Ca_2.34Fe_0.22Mg_0.03Na_0.01)_Σ4.99P_3.00O₁₂[Cl_0.48(OH)_0.41F_0.11]. The crystal structure of parafiniukite was refined to an R₁ = 0.0463 for 320 independent reflections with F_o > 4σ(F_o) and 41 refined parameters. Parafiniukite is isotypic with apatites. Manganese is the dominant cation at the M(2) site, and Ca is the dominant cation at the M(1) site. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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14 pages, 19168 KiB

Open AccessArticle

Nöggerathite-(Ce), (Ce,Ca)₂Zr₂(Nb,Ti)(Ti,Nb)₂Fe²⁺O₁₄, a New Zirconolite-Related Mineral from the Eifel Volcanic Region, Germany

by Nikita V. Chukanov, Natalia V. Zubkova, Sergey N. Britvin, Igor V. Pekov, Marina F. Vigasina, Christof Schäfer, Bernd Ternes, Willi Schüller, Yury S. Polekhovsky, Vera N. Ermolaeva and Dmitry Yu. Pushcharovsky

Minerals 2018, 8(10), 449; https://doi.org/10.3390/min8100449 - 12 Oct 2018

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Abstract

The new mineral nöggerathite-(Ce) was discovered in a sanidinite volcanic ejectum from the Laach Lake (Laacher See) paleovolcano in the Eifel region, Rhineland-Palatinate, Germany. Associated minerals are sanidine, dark mica, magnetite, baddeleyite, nosean, and a chevkinite-group mineral. Nöggerathite-(Ce) has a color that ranges [...] Read more.

The new mineral nöggerathite-(Ce) was discovered in a sanidinite volcanic ejectum from the Laach Lake (Laacher See) paleovolcano in the Eifel region, Rhineland-Palatinate, Germany. Associated minerals are sanidine, dark mica, magnetite, baddeleyite, nosean, and a chevkinite-group mineral. Nöggerathite-(Ce) has a color that ranges from brown to deep brownish red, with adamantine luster; the streak is brownish red. It occurs in cavities of sanidinite and forms long prismatic crystals measuring up to 0.02 × 0.03 × 1.0 mm, with twins and random intergrowths. Its density calculated using the empirical formula is 5.332 g/cm³. The Vickers hardness number (VHN) is 615 kgf/mm², which corresponds to a Mohs’ hardness of 5½. The mean refractive index calculated using the Gladstone–Dale equation is 2.267. The Raman spectrum shows the absence of hydrogen-bearing groups. The chemical composition (electron microprobe holotype/cotype in wt %) is as follows: CaO 5.45/5.29, MnO 4.19/4.16, FeO 7.63/6.62, Al₂O₃ 0.27/0.59, Y₂O₃ 0.00/0.90, La₂O₃ 3.17/3.64, Ce₂O₃ 11.48/11.22, Pr₂O₃ 1.04/0.92, Nd₂O₃ 2.18/2.46, ThO₂ 2.32/1.98, TiO₂ 17.78/18.69, ZrO₂ 27.01/27.69, Nb₂O₅ 17.04/15.77, total 99.59/99.82, respectively. The empirical formulae based on 14 O atoms per formula unit (apfu) are: (Ce_0.59La_0.165Nd_0.11Pr_0.05)_Σ0.915Ca_0.82Th_0.07Mn_0.50Fe_0.90Al_0.045Zr_1.86Ti_1.88Nb_1.07O₁₄ (holotype), and (Ce_0.57La_0.19Nd_0.12Pr_0.05Y_0.06)_Σ0.99Ca_0.79Th_0.06Mn_0.49Fe_0.77Al_0.10Zr_1.89Ti_1.96Nb_1.00O₁₄ (cotype). The simplified formula is (Ce,Ca)₂Zr₂(Nb,Ti)(Ti,Nb)₂Fe²⁺O₁₄. Nöggerathite-(Ce) is orthorhombic, of the space group Cmca. The unit cell parameters are: a = 7.2985(3), b = 14.1454(4), c = 10.1607(4) Å, and V = 1048.99(7) Å³. The crystal structure was solved using single-crystal X-ray diffraction data. Nöggerathite-(Ce) is an analogue of zirconolite-3O, ideally CaZrTi₂O₇, with Nb dominant over Ti in one of two octahedral sites and REE dominant over Ca in the eight-fold coordinated site. The strongest lines of the powder X-ray diffraction pattern (d, Å (I, %) (hkl)) are: 2.963 (91) (202), 2.903 (100) (042), 2.540 (39) (004), 1.823 (15) (400), 1.796 (51) (244), 1.543 (20) (442), and 1.519 (16) (282), respectively. The type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia (registration number 5123/1). Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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14 pages, 5364 KiB

Open AccessArticle

Cerromojonite, CuPbBiSe₃, from El Dragόn (Bolivia): A New Member of the Bournonite Group

by Hans-Jürgen Förster, Luca Bindi, Günter Grundmann and Chris J. Stanley

Minerals 2018, 8(10), 420; https://doi.org/10.3390/min8100420 - 21 Sep 2018

Cited by 10 | Viewed by 3502

Abstract

Cerromojonite, ideally CuPbBiSe₃, represents a new selenide from the El Dragόn mine, Department of Potosí, Bolivia. It either occurs as minute grains (up to 30 µm in size) in interstices of hansblockite/quijarroite intergrowths, forming an angular network-like intersertal texture, or as [...] Read more.

Cerromojonite, ideally CuPbBiSe₃, represents a new selenide from the El Dragόn mine, Department of Potosí, Bolivia. It either occurs as minute grains (up to 30 µm in size) in interstices of hansblockite/quijarroite intergrowths, forming an angular network-like intersertal texture, or as elongated, thin-tabular crystals (up to 200 μm long and 40 μm wide) within lath-shaped or acicular mineral aggregates (interpreted as pseudomorphs) up to 2 mm in length and 200 μm in width. It is non-fluorescent, black, and opaque, with a metallic luster and black streak. It is brittle, with an irregular fracture, and no obvious cleavage and parting. In plane-polarized incident light, cerromojonite is grey to cream-white, and weakly pleochroic, showing no internal reflections. Between crossed polarizers, cerromojonite is weakly anisotropic, with rotation tints in shades of brown and grey. Lamellar twinning on {110} is common. The reflectance values in air for the COM standard wavelengths (R₁ and R₂) are: 48.8 and 50.3 (470 nm), 48.2 and 51.8 (546 nm), 47.8 and 52.0 (589 nm), and 47.2 and 52.0 (650 nm). Electron-microprobe analyses yielded a mean composition of: Cu 7.91, Ag 2.35, Hg 7.42, Pb 16.39, Fe 0.04, Ni 0.02, Bi 32.61, Se 33.37, total 100.14 wt %. The empirical formula (based on 6 atoms pfu) is (Cu_0.89Hg_0.11)_{Σ = 1.00}(Pb_0.56Ag_0.16Hg_0.15 Bi_0.11Fe_0.01)_{Σ = 0.99}Bi_1.00Se_3.01. The ideal formula is CuPbBiSe₃. Cerromojonite is orthorhombic (space group Pn2₁m), with a = 8.202(1) Å, b = 8.741(1) Å, c = 8.029(1) Å, V = 575.7(1) Å³, Z = 4. Calculated density is 7.035 g·cm⁻³. The five strongest measured X-ray powder diffraction lines (d in Å (I/I₀) (hkl)) are: 3.86 (25) (120), 2.783 (100) (122), 2.727 (55) (212), 2.608 (40) (310), and 1.999 (25) (004). Cerromojonite is a new member of the bournonite group, representing the Se-analogue of součekite, CuPbBi(S,Se)₃. It is deposited from strongly oxidizing low-T hydrothermal fluids at a f_Se2/f_S2 ratio >1, both as primary and secondary phase. The new species has been approved by the IMA-CNMNC (2018-040) and is named for Cerro Mojon, the highest mountain peak closest to the El Dragón mine. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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9 pages, 1968 KiB

Open AccessArticle

Aurihydrargyrumite, a Natural Au₆Hg₅ Phase from Japan

by Daisuke Nishio-Hamane, Takahiro Tanaka and Tetsuo Minakawa

Minerals 2018, 8(9), 415; https://doi.org/10.3390/min8090415 - 19 Sep 2018

Cited by 9 | Viewed by 3930

Abstract

Aurihydrargyrumite, a natural Au₆Hg₅ phase, was found in Iyoki, Uchiko, Ehime Prefecture, Shikoku Island, Japan. Aurihydrargyrumite with a metallic silver luster occurs as a submicron- to 2 μm-thick layer on the outermost surface of the placer gold. A prismatic face [...] Read more.

Aurihydrargyrumite, a natural Au₆Hg₅ phase, was found in Iyoki, Uchiko, Ehime Prefecture, Shikoku Island, Japan. Aurihydrargyrumite with a metallic silver luster occurs as a submicron- to 2 μm-thick layer on the outermost surface of the placer gold. A prismatic face may be formed by {001} and {100} or {110}. The streak is also silver white and its Mohs hardness value is ca. 2.5. Its tenacity is ductile and malleable, and its density, as calculated based on the empirical formula and powder unit-cell data, is 16.86 g·cm⁻³. The empirical formula of aurihydrargyrumite, on the basis of 11 Au + Hg, is Au_5.95Hg_5.05. Aurihydrargyrumite is hexagonal, P6₃/mcm, with the lattice parameters a = 6.9960(10) Å, c = 10.154(2) Å and V = 430.40(15) Å³, which is identical with the synthetic Au₆Hg₅ phase. The seven strongest lines in the powder X-ray diffraction (XRD) pattern [d in Å(I/I₀)(hkl)] were 2.877(29)(112), 2.434(42)(113), 2.337(100)(104), 2.234(87)(211), 1.401(39)(314), 1.301(41)(404), and 1.225(65)(217). Aurihydrargyrumite forms through the weathering of mercury-bearing placer gold by involvement of self-electrorefining. This new mineral has been approved by the IMA-CNMNC (2017-003) and it is named for its composition, being a natural amalgam of gold (Latin: aurum) and mercury (Latin: hydrargyrum). Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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13 pages, 4312 KiB

Open AccessArticle

New Occurrence of Rusinovite, Ca₁₀(Si₂O₇)₃Cl₂: Composition, Structure and Raman Data of Rusinovite from Shadil-Khokh Volcano, South Ossetia and Bellerberg Volcano, Germany

by Dorota Środek, Rafał Juroszek, Hannes Krüger, Biljana Krüger, Irina Galuskina and Viktor Gazeev

Minerals 2018, 8(9), 399; https://doi.org/10.3390/min8090399 - 10 Sep 2018

Cited by 6 | Viewed by 4471

Abstract

Rusinovite, Ca₁₀(Si₂O₇)₃Cl₂, was found at two new localities, including Shadil-Khokh volcano, South Ossetia and Bellerberg volcano, Caspar quarry, Germany. At both of these localities, rusinovite occurs in altered carbonate-silicate xenoliths embedded in volcanic [...] Read more.

Rusinovite, Ca₁₀(Si₂O₇)₃Cl₂, was found at two new localities, including Shadil-Khokh volcano, South Ossetia and Bellerberg volcano, Caspar quarry, Germany. At both of these localities, rusinovite occurs in altered carbonate-silicate xenoliths embedded in volcanic rocks. The occurrence of this mineral is connected to specific zones of the xenolith characterized by a defined Ca:Si < 2 ratio. Chemical compositions, as well as the Raman spectra of the investigated rusinovite samples, correspond to the data from the locality of rusinovite holotype—Upper Chegem Caldera, Northern Caucasus, Russia. The most intense bands of the Raman spectra are related to vibrations of (Si₂O₇) groups. Unit cell parameters of rusinovite from South Ossetia are: a = 3.76330(4) Å, b = 16.9423(3) Å, c = 17.3325(2) Å, V = 1105.10(4) Å³, Z = 2. The performed synchrotron radiation diffraction experiments did not confirm a doubling of c as reported for the synthetic phase, Ca₁₀(Si₂O₇)₃Cl₂. However, one-dimensional diffuse scattering parallel to b* has been observed. This can be interpreted with an ordered arrangement of Si₂O₇ groups creating layers with a doubled a parameter. Consequently, the two different displacements of neighbouring layers allow random stacking faults to occur. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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16 pages, 4802 KiB

Open AccessArticle

Dynamic Disorder of Fe³⁺ Ions in the Crystal Structure of Natural Barioferrite

by Arkadiusz Krzątała, Taras L. Panikorovskii, Irina O. Galuskina and Evgeny V. Galuskin

Minerals 2018, 8(8), 340; https://doi.org/10.3390/min8080340 - 8 Aug 2018

Cited by 10 | Viewed by 4484

Abstract

A natural barioferrite, BaFe³⁺₁₂O₁₉, from a larnite–schorlomite–gehlenite vein of paralava within gehlenite hornfels of the Hatrurim Complex at Har Parsa, Negev Desert, Israel, was investigated by Raman spectroscopy, electron probe microanalysis, and single-crystal X-ray analyses acquired over the [...] Read more.

A natural barioferrite, BaFe³⁺₁₂O₁₉, from a larnite–schorlomite–gehlenite vein of paralava within gehlenite hornfels of the Hatrurim Complex at Har Parsa, Negev Desert, Israel, was investigated by Raman spectroscopy, electron probe microanalysis, and single-crystal X-ray analyses acquired over the temperature range of 100–400 K. The crystals are up to 0.3 mm × 0.1 mm in size and form intergrowths with hematite, magnesioferrite, khesinite, and harmunite. The empirical formula of the barioferrite investigated is as follows: (Ba_0.85Ca_0.12Sr_0.03)_∑1(Fe³⁺_10.72Al_0.46Ti⁴⁺_0.41Mg_0.15Cu²⁺_0.09Ca_0.08Zn_0.04Mn²⁺_0.03Si_0.01)_∑11.99O₁₉. The strongest bands in the Raman spectrum are as follows: 712, 682, 617, 515, 406, and 328 cm⁻¹. The structure of natural barioferrite (P6₃/mmc, a = 5.8901(2) Å, c = 23.1235(6) Å, V = 694.75(4) Å³, Z = 2) is identical with the structure of synthetic barium ferrite and can be described as an interstratification of two fundamental blocks: spinel-like S-modules with a cubic stacking sequence and R-modules that have hexagonal stacking. The displacement ellipsoids of the trigonal bipyramidal site show elongation along the [001] direction during heating. As a function of temperature, the mean apical Fe–O bond lengths increase, whereas the equatorial bond lengths decrease, which indicates dynamic disorder at the Fe2 site. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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14 pages, 8596 KiB

Open AccessArticle

Kurchatovite and Clinokurchatovite, Ideally CaMgB₂O₅: An Example of Modular Polymorphism

by Yulia A. Pankova, Sergey V. Krivovichev, Igor V. Pekov, Edward S. Grew and Vasiliy O. Yapaskurt

Minerals 2018, 8(8), 332; https://doi.org/10.3390/min8080332 - 2 Aug 2018

Cited by 5 | Viewed by 3487

Abstract

Kurchatovite and clinokurchatovite, both of ideal composition CaMgB₂O₅, from the type localities (Solongo, Buryatia, Russia, and Sayak-IV, Kazakhstan, respectively) have been studied using electron microprobe and single-crystal X-ray diffraction methods. The empirical formulae of the samples are Ca_1.01 [...] Read more.

Kurchatovite and clinokurchatovite, both of ideal composition CaMgB₂O₅, from the type localities (Solongo, Buryatia, Russia, and Sayak-IV, Kazakhstan, respectively) have been studied using electron microprobe and single-crystal X-ray diffraction methods. The empirical formulae of the samples are Ca_1.01Mg_0.87Mn_0.11Fe²⁺_0.02B_1.99O₅ and Ca_0.94Mg_0.91Fe²⁺_0.10Mn_0.04B_2.01O₅ for kurchatovite and clinokurchatovite, respectively. The crystal structures of the two minerals are similar and based upon two-dimensional blocks arranged parallel to the c axis in kurchatovite and parallel to the a axis in clinokurchatovite. The blocks are built up from diborate B₂O₅ groups, and Ca²⁺ and Mg²⁺ cations in seven- and six-fold coordination, respectively. Detailed analysis of geometrical parameters of the adjacent blocks reveals that symmetrically different diborate groups have different degrees of conformation in terms of the δ angles between the planes of two BO₃ triangles sharing a common O atom, featuring two discrete sets of the δ values of ca. 55° (B’ blocks) and 34° (B” blocks). The stacking of the blocks in clinokurchatovite can be presented as …(+B’)(+B”)(+B’)(+B”)… or [(+B’)(+B”)], whereas in kurchatovite it is more complex and corresponds to the sequence …(+B’)(+B”)(+B’)(−B’)(−B”)(−B’)(+B’)(+B”)(+B’)(−B’)(−B”)(−B’)… or [(+B’)(+B”)(+B’)(−B’)(−B”)(−B’)]. The B’:B” ratios for clinokurchatovite and kurchatovite are 1:1 and 2:1, respectively. According to this description, the two minerals cannot be considered as polytypes and their mutual relationship corresponds to the term modular polymorphs. From the viewpoint of information-based measures of structural complexity, clinokurchatovite (I_G = 4.170 bits/atom and I_G,total = 300.235 bits/cell) is structurally simpler than kurchatovite (I_G = 4.755 bits/atom and I_G,total = 1027.056 bits/cell). The high structural complexity of kurchatovite can be inferred from the modular character of its structure. The analysis of structural combinatorics in terms of the modular approach allows to construct the whole family of theoretically possible “kurchatovite”-type structures that bear the same structural features common for kurchatovite and clinokurchatovite. However, the crystal structures of the latter minerals are the simplest and are the only ones that have been observed in nature. The absence of other possible structures is remarkable and can be explained by either the maximum-entropy of the least-action fundamental principles. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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24 pages, 6221 KiB

Open AccessArticle

Sharyginite, Ca₃TiFe₂O₈, A New Mineral from the Bellerberg Volcano, Germany

by Rafał Juroszek, Hannes Krüger, Irina Galuskina, Biljana Krüger, Lidia Jeżak, Bernd Ternes, Justyna Wojdyla, Tomasz Krzykawski, Leonid Pautov and Evgeny Galuskin

Minerals 2018, 8(7), 308; https://doi.org/10.3390/min8070308 - 21 Jul 2018

Cited by 10 | Viewed by 5043

Abstract

The new mineral sharyginite, Ca₃TiFe₂O₈ (P2₁ma, Z = 2, a = 5.423(2) Å, b = 11.150(8) Å, c = 5.528(2) Å, V = 334.3(3) Å³), a member of the anion deficient [...] Read more.

The new mineral sharyginite, Ca₃TiFe₂O₈ (P2₁ma, Z = 2, a = 5.423(2) Å, b = 11.150(8) Å, c = 5.528(2) Å, V = 334.3(3) Å³), a member of the anion deficient perovskite group, was discovered in metacarbonate xenoliths in alkali basalt from the Caspar quarry, Bellerberg volcano, Eifel, Germany. In the holotype specimen, sharyginite is widespread in the contact zone of xenolith with alkali basalt. Sharyginite is associated with fluorellestadite, cuspidine, brownmillerite, rondorfite, larnite and minerals of the chlormayenite-wadalite series. The mineral usually forms flat crystals up to 100 µm in length, which are formed by pinacoids {100}, {010} and {001}. Crystals are flattened on (010). Sharyginite is dark brown, opaque with a brown streak and has a sub-metallic lustre. In reflected light, it is light grey and exhibits rare yellowish-brown internal reflections. The calculated density of sharyginite is 3.943 g·cm^-3. The empirical formula calculated on the basis of 8 O apfu is Ca_3.00(Fe³⁺_1.00Ti⁴⁺_0.86Mn⁴⁺_0.11Zr_0.01Cr³⁺_0.01Mg_0.01)_Σ2(Fe³⁺_0.76Al_0.20Si_0.04)_Σ1.00O₈. The crystal structure of sharyginite, closely related to shulamitite Ca₃TiFeAlO₈ structure, consists of double layers of corner-sharing (Ti, Fe³⁺) O₆ octahedra, which are separated by single layers of (Fe³⁺O₄) tetrahedra. We suggest that sharyginite formed after perovskite at high-temperature conditions >1000°C. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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10 pages, 2797 KiB

Open AccessEditor’s ChoiceArticle

Fiemmeite Cu₂(C₂O₄)(OH)₂∙2H₂O, a New Mineral from Val di Fiemme, Trentino, Italy

by Francesco Demartin, Italo Campostrini, Paolo Ferretti and Ivano Rocchetti

Minerals 2018, 8(6), 248; https://doi.org/10.3390/min8060248 - 12 Jun 2018

Cited by 6 | Viewed by 7289

Abstract

The new mineral species fiemmeite, Cu₂(C₂O₄)(OH)₂∙2H₂O, was found NE of the Passo di San Lugano, Val di Fiemme, Carano, Trento, Italy (latitude 46.312° N, longitude 11.406° E). It occurs in coalified woods [...] Read more.

The new mineral species fiemmeite, Cu₂(C₂O₄)(OH)₂∙2H₂O, was found NE of the Passo di San Lugano, Val di Fiemme, Carano, Trento, Italy (latitude 46.312° N, longitude 11.406° E). It occurs in coalified woods at the base of the Val Gardena Sandstone (upper Permian) which were permeated by mineralizing solutions containing Cu, U, As, Pb and Zn. The oxalate anions have originated from diagenesis of the plant remains included in sandstones. The mineral forms aggregate up to 1 mm across of sky blue platelets with single crystals reaching maximum dimensions of about 50 μm. Associated minerals are: baryte, olivenite, middlebackite, moolooite, brochantite, cuprite, devilline, malachite, azurite, zeunerite/metazeunerite, tennantite, chalcocite, galena. Fiemmeite is monoclinic, space group: P2₁/c with a = 3.4245(6), b = 10.141(2), c = 19.397(3) Å, β = 90.71(1)°, V = 673.6(2) Å³, Z = 4. The calculated density is 2.802 g/cm³ while the observed density is 2.78(1) g/cm³. The six strongest reflections in the X-ray powder diffraction pattern are: [d_obs in Å (I)(hkl)] 5.079(100)(020), 3.072(58)(112), 9.71(55)(002), 4.501(50)(022), 7.02(28)(012), 2.686(25)(114). The crystal structure was refined from single-crystal data to a final R₁ = 0.0386 for 1942 observed reflections [I > 2σ(I)] with all the hydrogen atoms located from a Difference–Fourier map. The asymmetric unit contains two independent Cu²⁺ cations that display a distorted square-bipyramidal (4+2) coordination, one oxalate anion, two hydroxyl anions and two water molecules. The coordination polyhedra of the two copper atoms share common edges to form polymeric rows running along [100] with composition [Cu₂(C₂O₄)(OH)₂∙2H₂O]_n. These rows are held together by a well-established pattern of hydrogen bonds between the oxalate oxygens not involved in the coordination to copper, the hydrogen atoms of the water molecules and the hydroxyl anions. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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9 pages, 16030 KiB

Open AccessArticle

Oyonite, Ag₃Mn₂Pb₄Sb₇As₄S₂₄, a New Member of the Lillianite Homologous Series from the Uchucchacua Base-Metal Deposit, Oyon District, Peru

by Luca Bindi, Cristian Biagioni and Frank N. Keutsch

Minerals 2018, 8(5), 192; https://doi.org/10.3390/min8050192 - 2 May 2018

Cited by 5 | Viewed by 4412

Abstract

The new mineral species oyonite, ideally Ag₃Mn₂Pb₄Sb₇As₄S₂₄, has been discovered in the Uchucchacua base-metal deposit, Oyon district, Catajambo, Lima Department, Peru, as very rare black metallic subhedral to anhedral crystals, up [...] Read more.

The new mineral species oyonite, ideally Ag₃Mn₂Pb₄Sb₇As₄S₂₄, has been discovered in the Uchucchacua base-metal deposit, Oyon district, Catajambo, Lima Department, Peru, as very rare black metallic subhedral to anhedral crystals, up to 100 μm in length, associated with orpiment, tennantite/tetrahedrite, menchettiite, and other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S, in calcite matrix. Its Vickers hardness (VHN₁₀₀) is 137 kg/mm² (range 132–147). In reflected light, oyonite is weakly to moderately bireflectant and weakly pleochroic from dark grey to a dark green. Internal reflections are absent. Reflectance values for the four COM wavelengths [R_min, R_max (%) (λ in nm)] are: 33.9, 40.2 (471.1); 32.5, 38.9 (548.3), 31.6, 38.0 (586.6); and 29.8, 36.5 (652.3). Electron microprobe analysis gave (in wt %, average of 5 spot analyses): Cu 0.76 (2), Ag 8.39 (10), Mn 3.02 (7), Pb 24.70 (25), As 9.54 (12), Sb 28.87 (21), S 24.30 (18), total 99.58 (23). Based on 20 cations per formula unit, the chemical formula of oyonite is Cu_0.38Ag_2.48Mn_1.75Pb_3.79Sb_7.55As_4.05S_24.12. The main diffraction lines are (d in Å, hkl and relative intensity): 3.34 (−312; 40), 3.29 (−520; 100), 2.920 (−132; 40), 2.821 (−232; 70), 2.045 (004; 50). The crystal structure study revealed oyonite to be monoclinic, space group P2₁/n, with unit-cell parameters a = 19.1806 (18), b = 12.7755 (14), c = 8.1789 (10) Å, β = 90.471 (11)°, V = 2004.1 (4) Å³, Z = 2. The crystal structure was refined to a final R₁ = 0.032 for 6272 independent reflections. Oyonite belongs to the Sb-rich members of the andorite homeotypic sub-series within the lillianite homologous series. The name oyonite is after the Oyon district, Lima Department, Peru, the district where the type locality (Uchucchacua mine) is located. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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13 pages, 1274 KiB

Open AccessArticle

Tiberiobardiite, Cu₉Al(SiO₃OH)₂(OH)₁₂(H₂O)₆(SO₄)_1.5·10H₂O, a New Mineral Related to Chalcophyllite from the Cretaio Cu Prospect, Massa Marittima, Grosseto (Tuscany, Italy): Occurrence and Crystal Structure

by Cristian Biagioni, Marco Pasero and Federica Zaccarini

Minerals 2018, 8(4), 152; https://doi.org/10.3390/min8040152 - 11 Apr 2018

Cited by 4 | Viewed by 4861

Abstract

The new mineral species tiberiobardiite, ideally Cu₉Al(SiO₃OH)₂(OH)₁₂(H₂O)₆(SO₄)_1.5·10H₂O, has been discovered in the Cretaio Cu prospect, Massa Marittima, Grosseto, Tuscany, Italy, as very rare, light green, [...] Read more.

The new mineral species tiberiobardiite, ideally Cu₉Al(SiO₃OH)₂(OH)₁₂(H₂O)₆(SO₄)_1.5·10H₂O, has been discovered in the Cretaio Cu prospect, Massa Marittima, Grosseto, Tuscany, Italy, as very rare, light green, vitreous, tabular {0001}, pseudo-hexagonal crystals, up to 200 μm in size and 5 μm in thickness, associated with brochantite. Electron microprobe analysis gave (in wt %, average of 5 spot analyses): SO₃ 10.37, P₂O₅ 3.41, As₂O₅ 0.05, SiO₂ 8.13, Al₂O₃ 5.54, Fe₂O₃ 0.74, CuO 62.05, and ZnO 0.03, for a total of 90.32. Based on an idealized O content of 42 atoms per formula unit, assuming the presence of 16 H₂O groups and 13.5 cations (without H), the empirical formula of tiberiobardiite is (Cu_8.69Al_0.21Fe_0.10)_Σ9.00Al_1.00(Si_1.51P_0.54)_Σ2.05S_1.44O_12.53(OH)_13.47·16H₂O. The main diffraction lines, corresponding to multiple hkl indices, are [d in Å (relative visual intensity)]: 9.4 (s), 4.67 (s), 2.576 (m), 2.330 (m), and 2.041 (mw). The crystal structure study revealed tiberiobardiite to be trigonal, space group R

\bar{3}

, with unit-cell parameters a = 10.6860(4), c = 28.3239(10) Å, V = 2801.0(2) Å³, and Z = 3. The crystal structure was refined to a final R₁ = 0.060 for 1747 reflections with F_o > 4σ (F_o) and 99 refined parameters. Tiberiobardiite is the Si-analogue of chalcophyllite, with Si⁴⁺ replacing As⁵⁺ through the coupled substitution As⁵⁺ + O²⁻ = Si⁴⁺ + (OH)⁻. The name tiberiobardiite honors Tiberio Bardi (b. 1960) for his contribution to the study of the mineralogy of Tuscany. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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14 pages, 4227 KiB

Open AccessEditor’s ChoiceArticle

New Mineral with Modular Structure Derived from Hatrurite from the Pyrometamorphic Rocks of the Hatrurim Complex: Ariegilatite, BaCa₁₂(SiO₄)₄(PO₄)₂F₂O, from Negev Desert, Israel

by Evgeny V. Galuskin, Biljana Krüger, Irina O. Galuskina, Hannes Krüger, Yevgeny Vapnik, Justyna A. Wojdyla and Mikhail Murashko

Minerals 2018, 8(3), 109; https://doi.org/10.3390/min8030109 - 8 Mar 2018

Cited by 17 | Viewed by 6226

Abstract

Ariegilatite, BaCa₁₂(SiO₄)₄(PO₄)₂F₂O (R

\bar{3}

m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å³, Z = 3), is a new member of the [...] Read more.

Ariegilatite, BaCa₁₂(SiO₄)₄(PO₄)₂F₂O (R

\bar{3}

m, a = 7.1551(6) Å, c = 41.303(3) Å, V = 1831.2(3) Å³, Z = 3), is a new member of the nabimusaite group exhibiting a modular intercalated antiperovskite structure derived from hatrurite. It was found in a few outcrops of pyrometamorphic rocks of the Hatrurim Complex located in the territories of Israel, Palestine and Jordan. The holotype specimen is an altered spurrite marble from the Negev Desert near Arad city, Israel. Ariegilatite is associated with spurrite, calcite, brownmillerite, shulamitite, CO₃-bearing fluorapatite, fluormayenite-fluorkyuygenite and a potentially new mineral, Ba₂Ca₁₈(SiO₄)₆(PO₄)₃(CO₃)F₃O. Ariegilatite is overgrown and partially replaced by stracherite, BaCa₆(SiO₄)₂[(PO₄)(CO₃)]F. The mineral forms flat disc-shaped crystals up to 0.5 mm in size. It is colorless, transparent, with white steaks and vitreous luster. Optically, ariegilatite is uniaxial, negative: ω = 1.650(2), ε = 1.647(2) (λ = 589 nm). The mean composition of the holotype ariegilatite, (Ba_0.98K_0.01Na_0.01)_Σ1(Ca_11.77Na_0.08Fe²⁺_0.06Mn²⁺_0.05Mg_0.04)_Σ12(Si_3.95Al_0.03Ti_0.02)_Σ4(P_1.70C_0.16Si_0.10S⁶⁺_0.03V_0.01)_Σ2F_2.04O_0.96, is close to the end-member formula. The structure of ariegilatite is described as a stacking of the two modules {F₂OCa₁₂(SiO₄)₄}⁴⁺ and {Ba(PO₄)₂}⁴⁻ along (001). Ariegilatite, as well as associated stracherite, are high-temperature alteration products of minerals of an early clinker-like association. These alterations took place under the influence of pyrometamorphism by-products, such as gases and fluids generated by closely-spaced combustion foci. Full article

(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)

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