Editorial

9 pages, 5724 KiB

Open AccessEditorial

Editorial for the Special Issue “Modern Raman Spectroscopy of Minerals”

by Thomas Schmid and Petra Dariz

Minerals 2020, 10(10), 860; https://doi.org/10.3390/min10100860 - 29 Sep 2020

Cited by 5 | Viewed by 3991

Raman spectroscopy provides vibrational fingerprints of chemical compounds, enabling their unambiguous identification [...] Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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Research

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21 pages, 36290 KiB

Open AccessArticle

Raman Microspectroscopy of Garnets from S-Fibulae from the Archaeological Site Lajh (Slovenia)

by Saša Kos, Matej Dolenec, Judita Lux and Sabina Dolenec

Minerals 2020, 10(4), 325; https://doi.org/10.3390/min10040325 - 04 Apr 2020

Cited by 16 | Viewed by 4497

Abstract

Garnets (19 pieces) of Late Antique S-fibulae from the archaeological site at Lajh-Kranj (Slovenia) were analysed with Raman microspectroscopy to obtain their mineral characteristic, including inclusion assemblage. Most garnets were determined as almandines Type I of pyralspite solid solution series; however, three garnets [...] Read more.

Garnets (19 pieces) of Late Antique S-fibulae from the archaeological site at Lajh-Kranj (Slovenia) were analysed with Raman microspectroscopy to obtain their mineral characteristic, including inclusion assemblage. Most garnets were determined as almandines Type I of pyralspite solid solution series; however, three garnets showed a higher Mg, Mn and Ca contents and were determined as almandines Type II. Most significant Raman bands were determined in the range of 169–173 cm⁻¹ (T(X²⁺)), 346–352 cm⁻¹ (R(SiO₄)), 557–559 cm⁻¹ (ν₂), 633–637 cm⁻¹ (ν₄), 917–919 cm⁻¹ (ν₁), and 1042–1045 cm⁻¹ (ν₃). Shifting of certain Raman bands toward higher frequencies was the result of an increase of the Mg content in the garnet composition, which also indicates the presence of pyrope end member in solid garnet solutions. Inclusions of apatite, quartz, mica, magnetite, ilmenite, as well as inclusions with pleochroic or radiation halo and tension fissures (zircon), were found in most of the garnets. Rutile and sillimanite were found only in garnets with the highest pyrope content. Spherical inclusions were also observed in two garnets, which may indicate the presence of melt or gas residues. The determined inclusion assemblage indicates the formation of garnets during medium- to high-grade metamorphism of amphibolite or granulite facies. According to earlier investigations of the garnets from Late Antique jewellery, the investigated garnets are believed to originate from India. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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18 pages, 6643 KiB

Open AccessEditor’s ChoiceArticle

In Situ Hyperspectral Raman Imaging of Ternesite Formation and Decomposition at High Temperatures

by Nadine Böhme, Kerstin Hauke, Manuela Neuroth and Thorsten Geisler

Minerals 2020, 10(3), 287; https://doi.org/10.3390/min10030287 - 21 Mar 2020

Cited by 16 | Viewed by 3589

Abstract

Knowledge of the high-temperature properties of ternesite (Ca₅(SiO₄)₂SO₄) is becoming increasingly interesting for industry in different ways. On the one hand, the high-temperature product has recently been observed to have cementitious properties. Therefore, its formation [...] Read more.

Knowledge of the high-temperature properties of ternesite (Ca₅(SiO₄)₂SO₄) is becoming increasingly interesting for industry in different ways. On the one hand, the high-temperature product has recently been observed to have cementitious properties. Therefore, its formation and hydration characteristics have become an important field of research in the cement industry. On the other hand, it forms as sinter deposits in industrial kilns, where it can create serious problems during kiln operation. Here, we present two highlights of in situ Raman spectroscopic experiments that were designed to study the high-temperature stability of ternesite. First, the spectra of a natural ternesite crystal were recorded from 25 to 1230 °C, which revealed a phase transformation of ternesite to the high-temperature polymorph of dicalcium silicate (α’_L-Ca₂SiO₄), while the sulfur is degassed. With a heating rate of 10 °C/h, the transformation started at about 730 °C and was completed at 1120 °C. Using in situ hyperspectral Raman imaging with a micrometer-scale spatial resolution, we were able to monitor the solid-state reactions and, in particular, the formation properties of ternesite in the model system CaO-SiO₂-CaSO₄. In these multi-phase experiments, ternesite was found to be stable between 930 to 1020–1100 °C. Both ternesite and α’_L-Ca₂SiO₄ were found to co-exist at high temperatures. Furthermore, the results of the experiments indicate that whether or not ternesite or dicalcium silicate crystallizes during quenching to room temperature depends on the reaction progress and possibly on the gas fugacity and composition in the furnace. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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14 pages, 5264 KiB

Open AccessArticle

Raman Study of Barite and Celestine at Various Temperatures

by Li Zhou, Terrence P. Mernagh, Bing Mo, Li Wang, Shuai Zhang and Chunyao Wang

Minerals 2020, 10(3), 260; https://doi.org/10.3390/min10030260 - 12 Mar 2020

Cited by 12 | Viewed by 3694

Abstract

The Raman spectra of barite and celestine were recorded from 25 to 600 °C at ambient pressure and both minerals were stable over the entire temperature range. Most of the Raman bands of barite decreased in wavenumber with increasing temperature with the exception [...] Read more.

The Raman spectra of barite and celestine were recorded from 25 to 600 °C at ambient pressure and both minerals were stable over the entire temperature range. Most of the Raman bands of barite decreased in wavenumber with increasing temperature with the exception of the ν₂ modes and the ν₄ band at 616 cm⁻¹, which did not exhibit a significant temperature dependence. These vibrations may be constrained by the lower thermal expansion along the a-axis and b-axis of barite. Similar to barite, most of the Raman bands of celestine also decreased in wavenumber with increasing temperature, with the exception of the ν₂ modes and the ν₄ band at 622 cm⁻¹, which showed very little variation with increasing temperature. Variations of Raman shift as a function of temperature and FWHM (full width at half maximum) as a function of Raman shift for the main, ν₁ modes of barite and celestine show that both minerals have almost identical linear trends with a slope of −0.02 cm⁻¹/°C and −0.5, respectively, which allows for the prediction of Raman shifts and FWHM up to much higher temperatures. The calculated isobaric and isothermal mode Grüneisen parameters and the anharmonicity parameters show that the M–O modes (M = Ba²⁺ and Sr²⁺) in barite and celestine exhibit much higher values of both mode Grüneisen parameters and anharmonicity than the SO₄ tetrahedra. This indicates that the S–O distances and S–O–S angles are less sensitive to pressure and temperature increase than the M–O distances in the structure. Furthermore, the generally higher anharmonicity in celestine is due to the smaller size of the Sr²⁺ cation, which causes the celestine structure to be more distorted than the barite structure. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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17 pages, 2458 KiB

Open AccessArticle

Evaluation of Bio-Based Extraction Methods by Spectroscopic Methods

by Mathilde Monachon, Magdalena Albelda-Berenguer, Tiziana Lombardo, Emilie Cornet, Friederike Moll-Dau, Janet Schramm, Katharina Schmidt-Ott and Edith Joseph

Minerals 2020, 10(2), 203; https://doi.org/10.3390/min10020203 - 24 Feb 2020

Cited by 8 | Viewed by 2797

Abstract

New technologies are in development regarding the preservation of waterlogged archaeological wood items contaminated with Fe/S species. To this purpose, a bio-based treatment to extract these harmful species before further damages occur is presented. Thiobacillus denitrificans and desferoxamine were employed based on their [...] Read more.

New technologies are in development regarding the preservation of waterlogged archaeological wood items contaminated with Fe/S species. To this purpose, a bio-based treatment to extract these harmful species before further damages occur is presented. Thiobacillus denitrificans and desferoxamine were employed based on their specific properties to solubilize iron sulfides and uptake iron. The biological treatment was compared with oxidizing and complexing agents (sodium persulfate and ethylene diamine tetraacetate) traditionally used in conservation-restoration. Mock-ups of fresh balsa as well as fresh and archeological oak and pinewood were prepared to simulate degraded waterlogged wood by immersion in corrosive Fe/S solutions. The efficiency of both biological and chemical extraction methods was evaluated through ATR-FTIR and Raman spectroscopies and validated by statistical approach. Results showed that treatments did not affect the wood composition, meaning that no wood degradation was induced. However, the chemical method tended to bleach the samples and after treatment, reduced sulfur species were still identified by Raman analyses. Finally, statistical approaches allowed validating ATR-FTIR results. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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16 pages, 3249 KiB

Open AccessFeature PaperArticle

Evaluation of a Spatial Heterodyne Spectrometer for Raman Spectroscopy of Minerals

by Alina Zettner, Ardian B. Gojani, Thomas Schmid and Igor B. Gornushkin

Minerals 2020, 10(2), 202; https://doi.org/10.3390/min10020202 - 24 Feb 2020

Cited by 10 | Viewed by 4580

Abstract

Spatial heterodyne spectroscopy (SHS) is a novel spectral analysis technique that is being applied for Raman spectroscopy of minerals. This paper presents the theoretical basis of SHS and its application for Raman measurements of calcite, quartz and forsterite in marble, copper ore and [...] Read more.

Spatial heterodyne spectroscopy (SHS) is a novel spectral analysis technique that is being applied for Raman spectroscopy of minerals. This paper presents the theoretical basis of SHS and its application for Raman measurements of calcite, quartz and forsterite in marble, copper ore and nickel ore, respectively. The SHS measurements are done using a broadband (518–686 nm) and resolving power

R \approx 3000

instrument. The spectra obtained using SHS are compared to those obtained by benchtop and modular dispersive spectrometers. It is found that SHRS performance in terms of resolution is comparable to that of the benchtop spectrometer and better than the modular dispersive spectrometer, while the sensitivity of SHRS is worse than that of a benchtop spectrometer, but better than that of a modular dispersive spectrometer. When considered that SHS components are small and can be packaged into a handheld device, there is interest in developing an SHS-based instrument for mobile Raman spectroscopy. This paper evaluates the possibility of such an application. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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35 pages, 11987 KiB

Open AccessArticle

Insights into the CaSO₄–H₂O System: A Raman-Spectroscopic Study

by Thomas Schmid, Robert Jungnickel and Petra Dariz

Minerals 2020, 10(2), 115; https://doi.org/10.3390/min10020115 - 29 Jan 2020

Cited by 22 | Viewed by 10245

Abstract

Even though being the subject of natural scientific research for many decades, the system CaSO₄–H₂O, consisting of the five crystalline phases gypsum, bassanite, and the anhydrites III, II, and I, has left many open questions for research. Raman spectroscopy [...] Read more.

Even though being the subject of natural scientific research for many decades, the system CaSO₄–H₂O, consisting of the five crystalline phases gypsum, bassanite, and the anhydrites III, II, and I, has left many open questions for research. Raman spectroscopy was used because of its structural sensitivity and in situ measurement capability to obtain further insight by studying phase transitions in both ex situ and in situ experiments. The findings include significant contributions to the completeness and understanding of Raman spectroscopic data of the system. The dehydration path gypsum–bassanite–anhydrite III was shown to have strong parallels to a physical drying process, which depends on many parameters beyond the burning temperature. Raman band width determination was demonstrated to enable the quantitative discrimination of α-bassanite and β-bassanite as well as the postulated three sub-forms of anhydrite II (AII), which are all based on differences in crystallinity. In the latter case, the observed continuous structural variations over increasing burning temperatures were elucidated as a combination of decreasing surface areas and healing of crystal lattice defects. We propose an only two-fold sub-division of AII into reactive “disordered AII” and much less reactive “crystalline AII” with a transition temperature of 650 °C ± 50 K. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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17 pages, 2415 KiB

Open AccessArticle

Fossil Resins–Constraints from Portable and Laboratory Near-infrared Raman Spectrometers

by Beata Naglik, Maja Mroczkowska-Szerszeń, Magdalena Dumańska-Słowik, Lucyna Natkaniec-Nowak, Przemysław Drzewicz, Paweł Stach and Grażyna Żukowska

Minerals 2020, 10(2), 104; https://doi.org/10.3390/min10020104 - 25 Jan 2020

Cited by 11 | Viewed by 3900

Abstract

Comparative studies of fossil resins of various ages, botanical sources, geological environments, and provenience were provided via a handheld portable Near-Infrared (NIR)-Raman spectrometer and benchtop instrument both working with laser line 1064 nm. The recorded Raman spectra of individual fossil resins were found [...] Read more.

Comparative studies of fossil resins of various ages, botanical sources, geological environments, and provenience were provided via a handheld portable Near-Infrared (NIR)-Raman spectrometer and benchtop instrument both working with laser line 1064 nm. The recorded Raman spectra of individual fossil resins were found to be sufficiently similar irrespective to the device type applied, i.e., handheld or benchtop. Thus, the portable equipment was found to be a sufficient tool for the preliminary identification of resins based on botanical and geographical origin criteria. The observed height ratio of 1640/1440 cm⁻¹ Raman bands did not correlate well with the ages of fossil resins. Hence, it may be assumed that geological conditions such as volcanic activity and/or hydrothermal heating are plausible factors accelerating the maturation of resins and cross-linking processes. Full article

(This article belongs to the Special Issue Modern Raman Spectroscopy of Minerals)

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