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3 pages, 206 KiB

Open AccessEditorial

Mineralogical Crystallography Volume II

by Vladislav V. Gurzhiy

Crystals 2022, 12(11), 1631; https://doi.org/10.3390/cryst12111631 - 13 Nov 2022

Cited by 1 | Viewed by 1046

Abstract

The International Mineralogical Association and UNESCO celebrates 2022—the Year of Mineralogy [...] Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

Research

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19 pages, 4498 KiB

Open AccessArticle

Gemological and Mineralogical Studies of Greenish Blue Apatite in Madagascar

by Zhi-Yi Zhang, Bo Xu, Peng-Yu Yuan and Zi-Xuan Wang

Crystals 2022, 12(8), 1067; https://doi.org/10.3390/cryst12081067 - 30 Jul 2022

Cited by 4 | Viewed by 2557

Abstract

Madagascar is known as the ‘Island of Gemstones’ because it is full of gemstone resources. Apatite from Madagascar is widely popular because of its greenish blue Paraiba-like color. This study analyzes apatite from Madagascar through standard gemological characteristic methods, spectroscopic tests and chemical [...] Read more.

Madagascar is known as the ‘Island of Gemstones’ because it is full of gemstone resources. Apatite from Madagascar is widely popular because of its greenish blue Paraiba-like color. This study analyzes apatite from Madagascar through standard gemological characteristic methods, spectroscopic tests and chemical analyses (i.e., electron probe and laser ablation inductively coupled plasma mass spectrometry). This work explores the gemological and the diagenesis information recorded on Madagascar apatite by comparing them with apatite from other sources and establishes the origin information of Madagascar apatite. The origin characteristics are as follows: Apatite from Madagascar is fluorapatite, with excellent diaphaneity, greenish–blue color caused by Ce and Nd and crystal structure distortion indicated by spectroscopic tests. The F/Cl ratio (16.47 to 21.89) suggests its magmatic origin Cl loss during the weathering processes forming the source rocks, and lg fO₂ (−10.30 to −10.35) reflects the high oxidation degree of magma. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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12 pages, 1851 KiB

Open AccessArticle

The Behavior of Water in Orthoclase Crystal and Its Implications for Feldspar Alteration

by Hongyan Zuo, Rui Liu and Anhuai Lu

Crystals 2022, 12(8), 1042; https://doi.org/10.3390/cryst12081042 - 27 Jul 2022

Cited by 5 | Viewed by 2243

Abstract

The phenomenon of feldspar alteration that occurs in the interior of feldspar crystals remains poorly understood. We observed experimentally that water can go into orthoclase crystals under pressures of up to 600 MPa at room temperature. With increasing pressure, the FTIR spectra of [...] Read more.

The phenomenon of feldspar alteration that occurs in the interior of feldspar crystals remains poorly understood. We observed experimentally that water can go into orthoclase crystals under pressures of up to 600 MPa at room temperature. With increasing pressure, the FTIR spectra of colorless orthoclase show a sharp increase in integral absorbance from 1.50 cm⁻¹ to 14.54 cm⁻¹ and normalized integral absorbance from 120 cm⁻² to 1570 cm⁻²; the pink orthoclase saturates quickly with no significant change in either the integral absorbance or normalized integral absorbance. The different responses to the pressure between colorless orthoclase and pink orthoclase might be related to the K content in the structure. Moreover, FTIR spectra at atmospheric pressure collected in different crystallography directions show different absorbance intensities, which illustrates the characteristic of preferred crystallographic orientations. These results reveal that H₂O molecules can occur as structural constituents entering the crystallographic channels of alkali feldspar crystals, preferentially along (001) orientation. These findings provide clues into the mechanism of feldspar alteration occurring in the interior of feldspar crystals, as well as the formation of micropores and microstructure in feldspar minerals. This study also provides important insights into the behavior of water molecules in nominally anhydrous minerals in the upper crust of the Earth. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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13 pages, 2829 KiB

Open AccessArticle

Natural Forsterite Strongly Enriched in Boron: Crystal Structure and Spectroscopy

by Bijie Peng, Mingyue He, Mei Yang, Shaokun Wu and Jingxin Fan

Crystals 2022, 12(7), 975; https://doi.org/10.3390/cryst12070975 - 12 Jul 2022

Cited by 3 | Viewed by 2491

Abstract

Boron is a typical crustal element and largely incompatible in olivine. Most natural olivine samples have very low concentrations of boron. Recently, forsterite with high boron content (up to 60.53 wt% MgO and 1795.91 ppm B) has been discovered in the Jian forsterite [...] Read more.

Boron is a typical crustal element and largely incompatible in olivine. Most natural olivine samples have very low concentrations of boron. Recently, forsterite with high boron content (up to 60.53 wt% MgO and 1795.91 ppm B) has been discovered in the Jian forsterite jade in the Jian area of northeast China. In this study, B-rich forsterite was examined by electron microprobes, Laser Ablation-Inductively Coupled Plasma Mass Spectrometry, Single crystal X-ray diffraction, Raman spectroscopy, and infrared spectroscopy. The B-rich forsterite is orthorhombic, existing in space group Pnma, and its unit-cell parameters are: a = 10.1918(7) Å, b = 5.9689(4) Å, c = 4.7484(3) Å, α = 90°, β = 90°, γ = 90°, and V = 288.86(3) Å³. The results of single crystal X-ray diffraction analysis indicate that the unit-cell parameters (a, b, and c) and unit-cell volume of forsterite in Jian forsterite jade are much smaller than those of known olivine. An equivalent set of Raman and infrared spectra were measured for the natural B-rich forsterite and compared to the results for mantle forsterite with a Fo value of ~91. The Raman spectrum of B-rich forsterite is similar to that of mantle olivine. We conclude that the systematic peak position shifts towards higher Raman shift with increasing Fo content. The infrared spectrum of B-rich forsterite crystals is characterized by strong absorption bands at 761, 1168, 1259, and 1303 cm⁻¹, which are assigned to stretching vibrations of BO₃ groups. Our data further confirm the existence of the B(F, OH)Si_–1O_–1 coupled substitution in natural B-rich forsterite. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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13 pages, 4329 KiB

Open AccessArticle

Near-Infrared Spectroscopic Study of OH Stretching Modes in Kaolinite and Dickite

by Shaokun Wu, Mingyue He, Mei Yang and Bijie Peng

Crystals 2022, 12(7), 907; https://doi.org/10.3390/cryst12070907 - 25 Jun 2022

Cited by 7 | Viewed by 2365

Abstract

Kaolinite and dickite are differently ordered polytypes of kaolinite-group minerals, whose differences are in the stacking mode of layers and ion occupation. Fourier transform infrared spectroscopy was used to collect information about the differences between the two minerals. The common characteristics of kaolinite [...] Read more.

Kaolinite and dickite are differently ordered polytypes of kaolinite-group minerals, whose differences are in the stacking mode of layers and ion occupation. Fourier transform infrared spectroscopy was used to collect information about the differences between the two minerals. The common characteristics of kaolinite and dickite are bands near 4530 and 7068 cm⁻¹, which are attributed to the combination of the inner Al-OH stretching vibration and outer Al-OH bending vibration and the overtone of the inner Al-OH stretching vibration, respectively. The difference is that kaolinite has secondary peaks at 4610 and 7177 cm⁻¹, and the secondary peak of dickite is near 4588 cm⁻¹. The OH stretching vibration has the first fundamental overtone of the stretching vibration in the range of 7000–7250 cm⁻¹. In addition to the overtones generated by single OH stretching vibrations, overtones combining different OH stretching vibrations are also found, which are formed by adjacent peaks of OH stretching vibrations. The average factor of the first fundamental overtone with an OH-group stretching vibration is approximately 1.95. The near-infrared spectrum (NIR) of phyllosilicates is closely related to their structure and isomorphism. Therefore, the near-infrared region can distinguish between kaolinite and dickite and provide a basis for deposit research and geological remote sensing. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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12 pages, 3885 KiB

Open AccessArticle

Mineralization Reaction of Calcium Nitrate and Sodium Silicate in Cement-Based Materials

by Isabel Miñano Belmonte, Mariano Calabuig Soler, Francisco J. Benito Saorin, Carlos J. Parra Costa, Carlos L. Rodríguez López, Jorge del Pozo Martin, Víctor Martinez Pacheco and Pilar Hidalgo Torrano

Crystals 2022, 12(4), 445; https://doi.org/10.3390/cryst12040445 - 23 Mar 2022

Cited by 3 | Viewed by 2909

Abstract

The research consists in the design of the new cementitious materials capable of mitigating microfisurative damage through autonomous healing. This lies in the characterization of the materials to employees, study of the expanding agents (sodium silicate and calcium nitrate) and analysis of its [...] Read more.

The research consists in the design of the new cementitious materials capable of mitigating microfisurative damage through autonomous healing. This lies in the characterization of the materials to employees, study of the expanding agents (sodium silicate and calcium nitrate) and analysis of its mechanical properties and durability. The results revealed that under laboratory conditions, the applied repair agents proved to be powerful in producing an increase in the content of ettringite, favoring the sealing of the fissure. When they heal themselves, they lead to an improvement in durability and mechanical performance. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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13 pages, 4464 KiB

Open AccessArticle

Characteristics of Channel-Water in Blue-Green Beryl and Its Influence on Colour

by Hui Wang, Tong Shu, Jingyi Chen and Ying Guo

Crystals 2022, 12(3), 435; https://doi.org/10.3390/cryst12030435 - 21 Mar 2022

Cited by 7 | Viewed by 2640

Abstract

This study reports the characteristics of water in channels of blue-green beryl and its effect on color. An industrial camera was used to measure color in the CIELAB color space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible (UV–vis) spectroscopy, and [...] Read more.

This study reports the characteristics of water in channels of blue-green beryl and its effect on color. An industrial camera was used to measure color in the CIELAB color space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible (UV–vis) spectroscopy, and silicate rock chemical analysis method were used for analysis. The peaks at 5105 cm⁻¹ and 5269 cm⁻¹ were the combination tone of type II water, which were negatively correlated with b*, and positively correlated with the peak area at 3162 cm⁻¹ (Na–H) and cell parameter a₀. The peaks at 7097 cm⁻¹ and 7142 cm⁻¹ were related to the metal ions types in the channels. Part of the water in the channel combined with Fe³⁺ to form [Fe₂(OH)₄]²⁺ and cause a yellow tone, and when the yellow tone combined with the blue tone caused by Fe²⁺, the beryl has a blue-green colour. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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13 pages, 1998 KiB

Open AccessArticle

A Synthetic Analog of the Mineral Ivanyukite: Sorption Behavior to Lead Cations

by Gleb O. Samburov, Galina O. Kalashnikova, Taras L. Panikorovskii, Vladimir N. Bocharov, Aleksandr Kasikov, Ekaterina Selivanova, Ayya V. Bazai, Daria Bernadskaya, Viktor N. Yakovenchuk and Sergey V. Krivovichev

Crystals 2022, 12(3), 311; https://doi.org/10.3390/cryst12030311 - 23 Feb 2022

Cited by 9 | Viewed by 2291

Abstract

The production of electrolytic nickel includes the stage of leaching of captured firing nickel matte dust. The solutions formed during this process contain considerable amounts of Pb, which is difficult to extraction due to its low concentration upon the high-salt background. The sorption [...] Read more.

The production of electrolytic nickel includes the stage of leaching of captured firing nickel matte dust. The solutions formed during this process contain considerable amounts of Pb, which is difficult to extraction due to its low concentration upon the high-salt background. The sorption of lead from model solutions with various compositions by synthetic and natural titanosilicate sorbents (synthetic ivanyukite-Na-T (SIV), ivanyukite-Na-T, and AM-4) have been investigated. The maximal sorption capacity of Pb is up to 400 mg/g and was demonstrated by synthetic ivanyukite In solutions with the high content of Cl⁻ (20 g/L), extraction was observed only with a high amount of Na (150 g/L). Molecular mechanisms and kinetics of lead incorporation into ivanyukite were studied by the combination of single-crystal and powder X-ray diffraction, microprobe analysis, and Raman spectroscopy. Incorporation of lead into natural ivanyukite-Na-T with the R3m symmetry by the substitution 2Na⁺ + 2O²⁻ ↔ Pb²⁺ + □ + 2OH⁻ leds to its transformation into the cubic P−43m Pb-exchanged form with the empirical formulae Pb_1.26[Ti₄O_2.52(OH)_1.48(SiO₄)₃]·3.32(H₂O). Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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15 pages, 6800 KiB

Open AccessArticle

Effect of Gold Nanoparticles on the Crystallization and Optical Properties of Glass in ZnO-MgO-Al₂O₃-SiO₂ System

by Georgiy Shakhgildyan, Veniamin Durymanov, Mariam Ziyatdinova, Grigoriy Atroshchenko, Nikita Golubev, Alexey Trifonov, Olga Chereuta, Leon Avakyan, Lusegen Bugaev and Vladimir Sigaev

Crystals 2022, 12(2), 287; https://doi.org/10.3390/cryst12020287 - 18 Feb 2022

Cited by 16 | Viewed by 3664

Abstract

Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of [...] Read more.

Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al₂O₃-SiO₂ glass containing TiO₂ and ZrO₂ as nucleating agents. X-ray diffraction, transmission electron microscopy, Raman, and optical spectroscopy were used for the study. We showed that gold nanoparticles have no effect on the formation of gahnite nanocrystals during the glass heat treatments, while optical properties of the glass-ceramics are strongly dependent on the gold addition. A computational model was developed to predict optical properties of glass during the crystallization, and the possibility for adjusting the localized surface plasmon resonance band position with the heat treatment temperature was shown. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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35 pages, 21326 KiB

Open AccessArticle

Optical and Spectroscopic Properties of Lorenzenite, Loparite, Perovskite, Titanite, Apatite, Carbonates from the Khibiny, Lovozero, Kovdor, and Afrikanda Alkaline Intrusion of Kola Peninsula (NE Fennoscandia)

by Miłosz Huber, Daniel Kamiński, Grzegorz Czernel and Evgeni Kozlov

Crystals 2022, 12(2), 224; https://doi.org/10.3390/cryst12020224 - 4 Feb 2022

Cited by 6 | Viewed by 2505

Abstract

This manuscript deals with the analysis of significant rare earth elements (REE) minerals such as eudialyte, lorenzenite, loparite, perovskite, titanite, apatite, and carbonates. These minerals are found in the rocks of the Khibiny, Lovozero, Afrikanda, and Kovdor massifs (the Paleozoic hotspot activity in [...] Read more.

This manuscript deals with the analysis of significant rare earth elements (REE) minerals such as eudialyte, lorenzenite, loparite, perovskite, titanite, apatite, and carbonates. These minerals are found in the rocks of the Khibiny, Lovozero, Afrikanda, and Kovdor massifs (the Paleozoic hotspot activity in the Kola-Karelian Alkaline Province is estimated at about 100,000 km²). Performed microscopic analyses that demonstrated their structure and optical features (dimming, interference colors, relief). Single-crystal analysis using XRD methods, SEM-EDS, and spectroscopic (FTIR) studies allowed the characteristics of described minerals: Lorenzenite in Lovozero probably crystalized after loparite have small additions of Nb, La, Ce, Pr, and Nd. Loparite and perovskite have the addition of Ce, Nb, and Ta. The same dopants have titanite probably crystalized after perovskite. Calcite in these massifs had the addition of Ce and Sr, the same as in fluorapatite, which was found in these rocks too. All of the analyzed minerals are REE-bearing and can be considered as deposits. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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12 pages, 4397 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

by Agus Pramono, Gerald Ensang Timuda, Ganang Pramudya Ahmad Rifai and Deni Shidqi Khaerudini

Crystals 2022, 12(1), 96; https://doi.org/10.3390/cryst12010096 - 13 Jan 2022

Cited by 4 | Viewed by 2715

Abstract

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage [...] Read more.

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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12 pages, 3816 KiB

Open AccessArticle

Natural Fluorite from Órgiva Deposit (Spain). A Study of Its Pozzolanic and Mechanical Properties

by Domingo A. Martín, Jorge Luis Costafreda, Esteban Estévez, Leticia Presa, Alicia Calvo, Ricardo Castedo, Miguel Ángel Sanjuán, José Luis Parra and Rafael Navarro

Crystals 2021, 11(11), 1367; https://doi.org/10.3390/cryst11111367 - 10 Nov 2021

Cited by 2 | Viewed by 1951

Abstract

This work presents the results of the partial substitution of Portland cement (PC) by natural fluorite (NF) and calcined fluorite (CF) in mortars, at 10%, 25% and 40%. To meet these objectives, a sample of fluorite was initially studied by XRD, SEM and [...] Read more.

This work presents the results of the partial substitution of Portland cement (PC) by natural fluorite (NF) and calcined fluorite (CF) in mortars, at 10%, 25% and 40%. To meet these objectives, a sample of fluorite was initially studied by XRD, SEM and Raman Spectroscopy (RS). A chemical quality analysis (CQA) and a chemical pozzolanicity test (CPT) at 8 and 15 days were carried out in a second stage to establish the pozzolanic properties of the investigated sample. Finally, a mechanical compressive strength test (MCST) at 7, 28 and 90 days was carried out on specimens made up with PC/NF and PC/CF mixes, at a ratio of 10%, 25% and 40%. XRD, SEM and RS results indicated fluorite as the major mineralogical phase. The CPT and CQA showed an increase in the pozzolanicity of the samples from 8 to 15 days. The MCST showed an increase in compressive strength from 7 to 90 days for both PC/NF and PC/CF specimens. The results obtained establish that fluorite produces positive effects in the mortar and contributes to the gain of mechanical strength over time, being a suitable material for the manufacture of cements with pozzolanic addition with a reduction of CO₂ emissions, and by reducing the energy costs of production. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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15 pages, 8039 KiB

Open AccessArticle

Preparation of NaA Zeolite from High Iron and Quartz Contents Coal Gangue by Acid Leaching—Alkali Melting Activation and Hydrothermal Synthesis

by Deshun Kong and Rongli Jiang

Crystals 2021, 11(10), 1198; https://doi.org/10.3390/cryst11101198 - 3 Oct 2021

Cited by 14 | Viewed by 2980

Abstract

In this study, NaA zeolite was successfully synthesized from coal gangue with high contents of iron and quartz as the main raw material. The results show that most iron ions can be removed from coal gangue after calcination at 700 °C for 2 [...] Read more.

In this study, NaA zeolite was successfully synthesized from coal gangue with high contents of iron and quartz as the main raw material. The results show that most iron ions can be removed from coal gangue after calcination at 700 °C for 2 h, leaching in hydrochloric acid with a mass fraction of 20% for 7 h and a liquid-solid ratio of 3.5:1. When m (acid leached residue of calcined gangue):m (Na₂CO₃) = 1.1 and melting at 750 °C for 2 h, the quartz and other aluminosilicates turn into nepheline, which dissolve in water. Finally, the optimum conditions of synthesis NaA zeolite are as follows: n(SiO₂)/n(Al₂O₃) = 2.0, n(Na₂O)/n(SiO₂) = 2.1, n(H₂O)/n(Na₂O) = 55, aging at 60 °C for 2 h, and crystallization at 94 °C for 4 h. This shows that the high iron and quartz contents coal gangue can be used for the synthesis of NaA zeolite. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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16 pages, 4812 KiB

Open AccessArticle

Morphology of Barite Synthesized by In-Situ Mixing of Na₂SO₄ and BaCl₂ Solutions at 200 °C

by Chunyao Wang, Li Zhou, Shuai Zhang, Li Wang, Chunwan Wei, Wenlei Song, Liping Xu and Wenge Zhou

Crystals 2021, 11(8), 962; https://doi.org/10.3390/cryst11080962 - 16 Aug 2021

Cited by 6 | Viewed by 2579

Abstract

Barite is an abundant sulfate mineral in nature. Especially, the variety of morphologies of barite is often driven by the mixing of Ba-bearing hydrothermal fluid and sulfate-bearing seawater around hydrothermal chimneys. In order to better understand the factors affecting the morphology and precipitation [...] Read more.

Barite is an abundant sulfate mineral in nature. Especially, the variety of morphologies of barite is often driven by the mixing of Ba-bearing hydrothermal fluid and sulfate-bearing seawater around hydrothermal chimneys. In order to better understand the factors affecting the morphology and precipitation mechanism(s) of barite in seafloor hydrothermal systems, we synthesized barite by a new method of in-situ mixing of BaCl₂ and Na₂SO₄ solutions at 200 °C while varying Ba concentrations and ratios of Ba²⁺/SO₄²⁻, and at room temperature for comparison. The results show that barite synthesized by in-situ mixing of BaCl₂ and Na₂SO₄ solutions at 200 °C forms a variety of morphologies, including rod-shaped, granular, plate-shaped, dendritic, X-shaped, and T-shaped morphologies, while room temperature barites display relatively simple, granular, or leaf-like morphologies. Thus, temperature affects barite morphology. Moreover, dendritic barite crystals only occurred at conditions where Ba²⁺ is in excess of SO₄²⁻ at the experimental concentrations. The dendritic morphology of barite may be an important typomorphic feature of barite formed in high-temperature fluids directly mixing with excess Ba²⁺ relative to SO₄²⁻. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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13 pages, 1404 KiB

Open AccessArticle

Crystal Chemical Relations in the Shchurovskyite Family: Synthesis and Crystal Structures of K₂Cu[Cu₃O]₂(PO₄)₄ and K_2.35Cu_0.825[Cu₃O]₂(PO₄)₄

by Ilya V. Kornyakov and Sergey V. Krivovichev

Crystals 2021, 11(7), 807; https://doi.org/10.3390/cryst11070807 - 11 Jul 2021

Cited by 3 | Viewed by 2928

Abstract

Single crystals of two novel shchurovskyite-related compounds, K₂Cu[Cu₃O]₂(PO₄)₄ (1) and K_2.35Cu_0.825[Cu₃O]₂(PO₄)₄ (2), were synthesized by crystallization from gaseous phase [...] Read more.

Single crystals of two novel shchurovskyite-related compounds, K₂Cu[Cu₃O]₂(PO₄)₄ (1) and K_2.35Cu_0.825[Cu₃O]₂(PO₄)₄ (2), were synthesized by crystallization from gaseous phase and structurally characterized using single-crystal X-ray diffraction analysis. The crystal structures of both compounds are based upon similar Cu-based layers, formed by rods of the [O₂Cu₆] dimers of oxocentered (OCu₄) tetrahedra. The topologies of the layers show both similarities and differences from the shchurovskyite-type layers. The layers are connected in different fashions via additional Cu atoms located in the interlayer, in contrast to shchurovskyite, where the layers are linked by Ca²⁺ cations. The structures of the shchurovskyite family are characterized using information-based structural complexity measures, which demonstrate that the crystal structure of 1 is the simplest one, whereas that of 2 is the most complex in the family. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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17 pages, 6174 KiB

Open AccessArticle

Bentonites in Southern Spain. Characterization and Applications

by Jorge Luis Costafreda and Domingo Alfonso Martín

Crystals 2021, 11(6), 706; https://doi.org/10.3390/cryst11060706 - 20 Jun 2021

Cited by 14 | Viewed by 2843

Abstract

The objective of this work was to investigate and demonstrate the pozzolanic properties of the bentonites found at the San José–Los Escullos deposit, located in the southeast of the Iberian Peninsula, to be used in the manufacturing of more durable and environmentally compatible [...] Read more.

The objective of this work was to investigate and demonstrate the pozzolanic properties of the bentonites found at the San José–Los Escullos deposit, located in the southeast of the Iberian Peninsula, to be used in the manufacturing of more durable and environmentally compatible pozzolanic cements, mortars and concretes. These bentonites are mainly composed of smectites, with montmorillonite as the main clay mineral. They were formed by the hydrothermal alteration of tuffs, volcanic glasses, dacites, rhyolites and andesites. For this research, samples were taken from outcrops on the south, north and west side of the San José–Los Escullos deposit, and in the Los Trancos deposit located 19.3 km to the northeast. All samples consisted of bentonites, except for a zeolite sample taken from the northern flank of the San José–Los Escullos deposit, which was used to contrast and compare the behaviour of bentonite in some of the analyses that were done. An investigation of the mineralogical, petrological, chemical and thermogravimetric characteristics of the samples was carried out using various methods, such as XRD, OA (Oriented aggregates), TGA, XRF, SEM and thin section petrography (TSP). In addition, a chemical analysis of pozzolanicity (CAP) was done at 8 and 15 days to determine the pozzolanic capacity of the samples. XRD, XRF, SEM and TSP studies showed that these bentonites have a complex mineralogical constitution, composed mainly of smectites of the montmorillonite variety, as well as halloysite, illite, vermiculite, biotite, muscovite, kaolinite, chlorite, mordenite, feldspar, pyroxene, amphibole, calcite, volcanic glass and quartz. Thermogravimetric analysis (TGA) established the thermal stability of the bentonites studied at above 800 °C. Chemical analysis of pozzolanicity (CAP) confirmed the pozzolanic character of the bentonites, exhibited in their reactive behaviour with Ca(OH)₂. The pozzolanic reactivity increased significantly from 8 to 15 days. These results show that the materials studied can be used as quality pozzolans for the manufacture of pozzolanic cements, mortars and concretes. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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Review

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23 pages, 6025 KiB

Open AccessReview

Crystal Chemistry and Structural Complexity of the Uranyl Carbonate Minerals and Synthetic Compounds

by Vladislav V. Gurzhiy, Sophia A. Kalashnikova, Ivan V. Kuporev and Jakub Plášil

Crystals 2021, 11(6), 704; https://doi.org/10.3390/cryst11060704 - 19 Jun 2021

Cited by 17 | Viewed by 3706

Abstract

Uranyl carbonates are one of the largest groups of secondary uranium(VI)-bearing natural phases being represented by 40 minerals approved by the International Mineralogical Association, overtaken only by uranyl phosphates and uranyl sulfates. Uranyl carbonate phases form during the direct alteration of primary U [...] Read more.

Uranyl carbonates are one of the largest groups of secondary uranium(VI)-bearing natural phases being represented by 40 minerals approved by the International Mineralogical Association, overtaken only by uranyl phosphates and uranyl sulfates. Uranyl carbonate phases form during the direct alteration of primary U ores on contact with groundwaters enriched by CO₂, thus playing an important role in the release of U to the environment. The presence of uranyl carbonate phases has also been detected on the surface of “lavas” that were formed during the Chernobyl accident. It is of interest that with all the importance and prevalence of these phases, about a quarter of approved minerals still have undetermined crystal structures, and the number of synthetic phases for which the structures were determined is significantly inferior to structurally characterized natural uranyl carbonates. In this work, we review the crystal chemistry of natural and synthetic uranyl carbonate phases. The majority of synthetic analogs of minerals were obtained from aqueous solutions at room temperature, which directly points to the absence of specific environmental conditions (increased P or T) for the formation of natural uranyl carbonates. Uranyl carbonates do not have excellent topological diversity and are mainly composed of finite clusters with rigid structures. Thus the structural architecture of uranyl carbonates is largely governed by the interstitial cations and the hydration state of the compounds. The information content is usually higher for minerals than for synthetic compounds of similar or close chemical composition, which likely points to the higher stability and preferred architectures of natural compounds. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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