Research

12 pages, 21677 KiB

Open AccessArticle

EMPA, XRD, and Raman Characterization of Ag-Bearing Djurleite from the Lubin Mine, Lower Silesia, Poland

by Krzysztof Szopa, Tomasz Krzykawski, Kamila Banasik, Piotr Król, Sylwia Skreczko, Stefania Andriopoulou Mounteanou and Marta Koziarska

Minerals 2021, 11(5), 454; https://doi.org/10.3390/min11050454 - 26 Apr 2021

Cited by 4 | Viewed by 2402

Abstract

The chalcocite group minerals are widely distributed among different hydrothermally affected rocks, the oxidized zone of copper sulfide deposits, or may be even crystalline from supersaturated volcanic gases. Some of the chalcocite group minerals form the main Cu orebodies. Djurleite (Cu₃₁S [...] Read more.

The chalcocite group minerals are widely distributed among different hydrothermally affected rocks, the oxidized zone of copper sulfide deposits, or may be even crystalline from supersaturated volcanic gases. Some of the chalcocite group minerals form the main Cu orebodies. Djurleite (Cu₃₁S₁₆) is a rare member of the chalcocite group, with a very complex structure. The physical and chemical similarities between all members of the group make them almost unidentifiable by macroscopic and microscopic methods. In this study, Ag-bearing djurleite from the Kupferschiefer deposits, Lower Silesia, Poland, is characterized by EMPA (Electron Microprobe Analyses), XRD (X-Ray Diffraction), and Raman spectroscopy. Djurleite from the investigated site has the following general, average chemical formula: Cu_30.86Ag_0.1Fe_0.04S₁₆. The Ag content is up to 0.55 wt.%, while Fe is up to 0.19 wt.%. The presence of djurleite confirms a low-temperature (~90 °C), hydrothermal origin of the Cu-Ag deposit in Kupferschiefer, which is consistent with previously studies. Moreover, the authors believe that Ag-rich djurleite may often be mistaken for Ag-rich chalcocite, which used to be one of the main Ag-bearing minerals in the orebody from the Cu-Ag deposit in the Fore-Sudetic Monocline. However, the confirmation of such a statement requires more samples, which should be studied in detail. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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24 pages, 11348 KiB

Open AccessArticle

Spectroscopic and Crystal-Chemical Features of Sodalite-Group Minerals from Gem Lazurite Deposits

by Nikita V. Chukanov, Anatoly N. Sapozhnikov, Roman Yu. Shendrik, Marina F. Vigasina and Ralf Steudel

Minerals 2020, 10(11), 1042; https://doi.org/10.3390/min10111042 - 23 Nov 2020

Cited by 29 | Viewed by 4438

Abstract

Five samples of differently colored sodalite-group minerals from gem lazurite deposits were studied by means of electron microprobe and wet chemical analyses, infrared, Raman, electron spin resonance (ESR) and UV-Visible spectroscopy, and X-ray diffraction. Various extra-framework components (SO₄²⁻, S²⁻ [...] Read more.

Five samples of differently colored sodalite-group minerals from gem lazurite deposits were studied by means of electron microprobe and wet chemical analyses, infrared, Raman, electron spin resonance (ESR) and UV-Visible spectroscopy, and X-ray diffraction. Various extra-framework components (SO₄²⁻, S²⁻ and Cl⁻ anions, S₃^•−, S₂^•− and SO₃^•− radical anions, H₂O, CO₂, COS, cis- as well as trans- or gauche-S₄ neutral molecules have been identified. It is shown that S₃^•− and S₄ are the main blue and purple chromophores, respectively, whereas the S₂^•− yellow chromophore and SO₃^•− blue chromophore play a subordinate role. X-ray diffraction patterns of all samples of sodalite-group minerals from lazurite deposits studied in this work contain superstructure reflections which indicate different kinds of incommensurate modulation of the structures. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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17 pages, 1297 KiB

Open AccessArticle

Micro-Raman—A Tool for the Heavy Mineral Analysis of Gold Placer-Type Deposits (Pianu Valley, Romania)

by Andreea Elena Maftei, Andrei Buzatu, Gheorghe Damian, Nicolae Buzgar, Harald G. Dill and Andrei Ionut Apopei

Minerals 2020, 10(11), 988; https://doi.org/10.3390/min10110988 - 07 Nov 2020

Cited by 19 | Viewed by 3933

Abstract

In the current study, different heavy minerals typical of gold placer deposits were identified by means of micro-Raman spectroscopy, and their chemical composition analyzed and discussed (garnet, kyanite, staurolite, zircon, allanite, monazite, xenotime, rutile, anatase, cassiterite, titanite, barite). Even complex solid solution series, [...] Read more.

In the current study, different heavy minerals typical of gold placer deposits were identified by means of micro-Raman spectroscopy, and their chemical composition analyzed and discussed (garnet, kyanite, staurolite, zircon, allanite, monazite, xenotime, rutile, anatase, cassiterite, titanite, barite). Even complex solid solution series, such as those of garnets, can be deciphered with the aid of systematic trends observed in Raman line frequencies. The ν₁ mode in garnets will shift from high to low frequencies as a function of the ionic radius of the X²⁺ cation, from Mg²⁺, to Fe²⁺ and Mn²⁺, while the presence of Ca²⁺ will make the band to be shifted strongly to even lower wavenumbers. This approach has successfully been taken to differentiate between polymorph triplets such as kyanite-sillimanite-andalusite and rutile-anatase-brookite. Minerals under consideration with high contents of REE, U and Th are affected by intensive metamictization, particularly zircon and titanite. Raman peak features, such as shape, symmetry and intensity, respond to this radiation damage of the lattice and enable fine-tuning of these heavy minerals, such as in the case of fluorite (fetid fluorite). Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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18 pages, 2378 KiB

Open AccessArticle

Structural Modifications of Single-Crystal Aragonite CaCO₃ Beginning at ~15 GPa: In Situ Vibrational Spectroscopy and X-Ray Diffraction Evidence

by Jing Gao, Yungui Liu, Xiang Wu, Xueyin Yuan, Yingxin Liu and Wen Su

Minerals 2020, 10(10), 924; https://doi.org/10.3390/min10100924 - 19 Oct 2020

Cited by 7 | Viewed by 3511

Abstract

The structural chemistry of carbonates under mantle conditions facilitates our understanding of carbon recycling pathways in the earth’s interior. It also has impacts on the dynamics of mantle–slab interactions. Aragonite is a common calcium carbonate mineral in pelagic marine sediments. The structural chemistry [...] Read more.

The structural chemistry of carbonates under mantle conditions facilitates our understanding of carbon recycling pathways in the earth’s interior. It also has impacts on the dynamics of mantle–slab interactions. Aragonite is a common calcium carbonate mineral in pelagic marine sediments. The structural chemistry of single-crystal aragonite during successive compression and the behavior of a structural H⁺ have been investigated by micro-vibrational spectroscopy and synchrotron X-ray diffraction techniques in diamond anvil cells. We describe a reduction of the b-axial compressibility beginning at ~15 GPa, and the related discontinuities in the first-order derivatives of the vibrational modes. The structural modifications of aragonite are manifested by mutations occurring in the pressure relations of the wavenumbers of the O-C-O bending modes, and of the bandwidth and band intensities of the measured internal and external modes. These anomalies are indicative of changes occurring in the force constant of the C-O bonds, and possibly a second-order phase transition. Besides, the [CaO₉] polyhedra begin to deform, possibly with some Ca-O bonds becoming elongated and the others shortening. An increase in the co-ordination number for the Ca²⁺ sites could be expected under higher pressures. Additionally, the weakening of the OH modes may imply H⁺-loss from the aragonite lattice above 11.5 GPa. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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13 pages, 3134 KiB

Open AccessArticle

Infrared and Raman Spectroscopy of Ammoniovoltaite, (NH₄)₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂(H₂O)₁₈

by Anastasia V. Sergeeva, Elena S. Zhitova, Anton A. Nuzhdaev, Andrey A. Zolotarev, Vladimir N. Bocharov and Rezeda M. Ismagilova

Minerals 2020, 10(9), 781; https://doi.org/10.3390/min10090781 - 03 Sep 2020

Cited by 17 | Viewed by 4001

Abstract

Ammoniovoltaite, (NH₄)₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂(H₂O)₁₈, is a complex hydrated sulphate of the voltaite group that has been recently discovered on the surface of the Severo-Kambalny geothermal field (Kamchatka, [...] Read more.

Ammoniovoltaite, (NH₄)₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂(H₂O)₁₈, is a complex hydrated sulphate of the voltaite group that has been recently discovered on the surface of the Severo-Kambalny geothermal field (Kamchatka, Russia). Vibrational spectroscopy has been applied for characterization of the mineral. Both infrared and Raman spectra of ammoniovoltaite are characterized by an abundance of bands, which corresponds to the diversity of structural fragments and variations of their local symmetry. The infrared spectrum of ammoniovoltaite is similar to that of other voltaite-related compounds. The specific feature related to the dominance of the NH₄ group is its ν₄ mode observed at 1432 cm⁻¹ with a shoulder at 1510 cm⁻¹ appearing due to NH₄ disorder. The Raman spectrum of ammoniovoltaite is basically different from that of voltaite by the appearance of an intensive band centered at 3194 cm⁻¹ and attributed to the ν₃ mode of NH₄. The latter can serve as a distinctive feature of ammonium in voltaite-group minerals in resemblance to recently reported results for another NH₄-mineral—tschermigite, where ν₃ of NH₄ occurs at 3163 cm⁻¹. The values calculated from wavenumbers of infrared bands at 3585 cm⁻¹, 3467 cm⁻¹ and 3400 cm⁻¹ for hydrogen bond distances: d(O···H) and d(O···O) correspond to bonding involving H1 and H2 atoms of Fe²⁺X₆ (X = O, OH) octahedra. The infrared bands observed at 3242 cm⁻¹ and 2483 cm⁻¹ are due to stronger hydrogen bonding, that may refer to non-localized H atoms of Al(H₂O)₆ or NH₄. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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11 pages, 1718 KiB

Open AccessArticle

Molecular Hydrogen in Natural Mayenite

by Evgeny Galuskin, Irina Galuskina, Yevgeny Vapnik and Mikhail Murashko

Minerals 2020, 10(6), 560; https://doi.org/10.3390/min10060560 - 22 Jun 2020

Cited by 8 | Viewed by 2289

Abstract

In the last 15 years, zeolite-like mayenite, Ca₁₂Al₁₄O₃₃, has attracted significant attention in material science for its variety of potential applications and for its simple composition. Hydrogen plays a key role in processes of electride material synthesis [...] Read more.

In the last 15 years, zeolite-like mayenite, Ca₁₂Al₁₄O₃₃, has attracted significant attention in material science for its variety of potential applications and for its simple composition. Hydrogen plays a key role in processes of electride material synthesis from pristine mayenite: {Ca₁₂Al₁₄O₃₂}²⁺(O²) → {Ca₁₂Al₁₄O₃₂}²⁺(e⁻)₂. A presence of molecular hydrogen in synthetic mayenite was not confirmed by the direct methods. Spectroscopy investigations of mayenite group mineral fluorkyuygenite, with empirical formula (Ca_12.09Na_0.03)_∑12.12(Al_13.67Si_0.12Fe³⁺_0.07Ti⁴⁺_0.01)_∑12.87O_31.96 [F_2.02Cl_0.02(H₂O)_3.22(H₂S)_0.15□_0.59]_∑6.00, show the presence of an unusual band at 4038 cm⁻¹, registered for the first time and related to molecular hydrogen, apart from usual bands responding to vibrations of mayenite framework. The band at 4038 cm⁻¹ corresponding to stretching vibrations of H₂ is at lower frequencies in comparison with positions of analogous bands of gaseous H₂ (4156 cm⁻¹) and H₂ adsorbed at active cation sites of zeolites (4050–4100 cm⁻¹). This points out relatively strong linking of molecular hydrogen with the fluorkyuygenite framework. An appearance of H₂ in the fluorkyuyginite with ideal formula Ca₁₂Al₁₄O₃₂[(H₂O)₄F₂], which formed after fluormayenite, Ca₁₂Al₁₄O₃₂[□₄F₂], is connected with its genesis. Fluorkyuygenite was detected in gehlenite fragments within brecciaed pyrometamorphic rock (Hatrurim Basin, Negev Desert, Israel), which contains reduced mineral assemblage of the Fe-P-C system (native iron, schreibersite, barringerite, murashkoite, and cohenite). The origin of phosphide-bearing associations is connected with the effect of highly reduced gases on earlier formed pyrometamorphic rocks. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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17 pages, 8457 KiB

Open AccessEditor’s ChoiceArticle

Extra-Framework Content in Sodalite-Group Minerals: Complexity and New Aspects of Its Study Using Infrared and Raman Spectroscopy

by Nikita V. Chukanov, Marina F. Vigasina, Natalia V. Zubkova, Igor V. Pekov, Christof Schäfer, Anatoly V. Kasatkin, Vasiliy O. Yapaskurt and Dmitry Yu. Pushcharovsky

Minerals 2020, 10(4), 363; https://doi.org/10.3390/min10040363 - 17 Apr 2020

Cited by 30 | Viewed by 4574

Abstract

Nine samples of carbonate-free sodalite-group minerals, including those with abnormally high contents of polysulfide groups, fluoride anion and carbon dioxide molecules as well as synthetic fluoraluminate sodalite-type compound Na₈(Si₇Al₅O₂₄)(AlF₆)^3–·5H₂O, [...] Read more.

Nine samples of carbonate-free sodalite-group minerals, including those with abnormally high contents of polysulfide groups, fluoride anion and carbon dioxide molecules as well as synthetic fluoraluminate sodalite-type compound Na₈(Si₇Al₅O₂₄)(AlF₆)^3–·5H₂O, have been studied by means of electron microprobe analyses, infrared and Raman spectroscopy; the CO₂ content was determined using the selective sorption of gaseous ignition products. This article describes a semi-quantitative method for estimating the content of carbon dioxide molecules in these minerals, based on IR spectroscopy data. The data obtained demonstrate the existence of a sulfide sodalite-group mineral with the idealized formula Na₇(Si₆Al₆O₂₄)(S₃⁻)·H₂O, which differs significantly from the formula Na₆Ca₂(Si₆Al₆O₂₄)S^2–₂ accepted for lazurite. According to single-crystal X-ray structural analysis, in the F-rich sodalite-group mineral from the Eifel paleovolcanic region, Germany with the idealized formula Na₇(Si₆Al₆O₂₄)F⁻·nH₂O fluorine occurs as an isolated F⁻ anion, unlike synthetic F-rich sodalite-type compounds. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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14 pages, 2267 KiB

Open AccessFeature PaperArticle

Vibrational Investigation of Pressure-Induced Phase Transitions of Hydroxycarbonate Malachite Cu₂(CO₃)(OH)₂

by Jing Gao and Xueyin Yuan

Minerals 2020, 10(3), 277; https://doi.org/10.3390/min10030277 - 19 Mar 2020

Cited by 6 | Viewed by 2942

Abstract

Malachite Cu₂(CO₃)(OH)₂ is a common hydroxycarbonate that contains about 15.3 wt % H₂O. Its structural chemistry sheds light on other hydroxyl minerals that play a role in the water recycling of our planet. Here using Raman [...] Read more.

Malachite Cu₂(CO₃)(OH)₂ is a common hydroxycarbonate that contains about 15.3 wt % H₂O. Its structural chemistry sheds light on other hydroxyl minerals that play a role in the water recycling of our planet. Here using Raman and infrared spectroscopy measurements, we studied the vibrational characteristics and structural evolution of malachite in a diamond anvil cell at room temperature (25 °C) up to ~29 GPa. Three types of vibrations were analyzed including Cu–O vibrations (300–600 cm⁻¹), [CO₃]²⁻ vibrations (700–1600 cm⁻¹), and O–H stretches (3200–3500 cm⁻¹). We present novel observations of mode discontinuities at pressures of ~7, ~15, and ~23 GPa, suggesting three phase transitions, respectively. First, pressure has a great effect on the degree of deformation of the [CuO₆] octahedron, as is manifested by the various shifting slopes of the Cu–O modes. [CuO₆] deformation results in a rotation of the structural unit and accordingly a phase transition at ~7 GPa. Upon compression to ~15 GPa, the O–H bands redshift progressively with significant broadness, indicative of an enhancement of the hydrogen bonding, a shortening of the O···O distance, and possibly somewhat of a desymmetrization of the O–H···O bond. O–H mode hardening is identified above ~15 GPa coupled with a growth in the amplitude of the lower-energy bands. These observations can be interpreted as some reorientation or reordering of the hydrogen bonding. A further increment of pressure leads to a change in the overall compression mechanism of the structure at ~23 GPa, which is characterized by the blueshift of the O–H stretches and the softening of the O–C–O in-plane bending bands. The hydrogen bonding weakens due to a substantial enhancement of the Cu–H repulsion effect, and the O···O bond length shows no further shortening. In addition, the change in the local geometry of hydrogen is also induced by the softening of the [CO₃]²⁻ units. In this regard we may expect malachite and other analogous hydroxyl minerals as capable of transporting water downward towards the Earth’s transition zone (~23 GPa). Our results furnish our knowledge on the chemistry of hydrogen bonding at mantle conditions and open a new window in understanding the synergistic relations of water and carbon recycling in the deep Earth. Full article

(This article belongs to the Special Issue Vibrational (Infrared and Raman) Spectroscopy of Minerals)

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