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Mineralogical Crystallography (3rd Edition)

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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Mineralogical Crystallography and Biomineralization".

Deadline for manuscript submissions: closed (15 December 2023) | Viewed by 19195

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Dr. Vladislav V. Gurzhiy

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Department Crystallography, Institute of Earth Sciences, St.Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Interests: crystallography; mineralogy; X-ray diffraction; uranium; inorganic chemistry; radiochemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Crystallography remains for mineralogy one of the main sources of information about natural crystalline substances. Additionally, it should be noted that International Mineralogical Association and UNESCO celebrates 2022 – the Year of Mineralogy. 2022 is the bicentennial of the death of René Just Haüy (born 1743) who is considered to be one of the founders of crystallography and mineralogy in their modern state. 1822 is also when Haüy’s Traité de minéralogy and Traité de cristallographie were published. Mineralogy is one of the oldest branches of science with its origin in at least antic times, but its scientific renaissance have started a little more than a century ago, when precise crystallographic studies, such as X-ray structural analysis (mainly, but not only), significantly improved the value of research results. Since the first decade of the XX century mineralogy and crystallography together play a key role in our everyday lives. This Special Issue is devoted to mineralogical crystallography, the oldest branch of crystallographic science, and aims to combine important surveys covering topics indicated in the keywords below.

The first Volume of the “Mineralogical Crystallography” Special Issue (https://www.mdpi.com/journal/crystals/special_issues/mineralogical_crystallography) features eleven important surveys covering such topics as: discovery of new mineral species; crystal chemistry of minerals and their synthetic analogs; behavior of minerals at non-ambient conditions; biomineralogy; and crystal growth techniques. The number of papers within the “Mineralogical Crystallography Volume II” has increased to sixteen and their distribution has also slightly changed: Crystal chemistry and properties of minerals and their synthetic analogs; Gemology; Natural-based cement materials; Biomineralogy; and Crystal growth techniques. Both Special Issues appeared to be very fruitful, so these online issues have been also published as printed book versions (https://www.mdpi.com/books/pdfview/book/2952 and https://www.mdpi.com/books/book/6452). This tendency demonstrates an increasing interest in the crystallography of natural phases and mineral-like synthetic compounds.

We hope that the continuation will keep the bar at the same significant height, and the new set of reviews and articles will again arouse genuine interest among readers and, perhaps, push them to their own successful research. So, we are very pleased to announce that the third Volume of the “Mineralogical Crystallography” Special Issue is now open to receive your manuscripts. Additionally, what is even more pleasant, the Special Issue "Mineralogical Crystallography Volume III" is announced to be open in 2022, thus celebrating the Year of Mineralogy.

We invite you to participate in this Issue and to contribute your research results in the fields of new mineral species discovery, structural studies of minerals and related synthetic materials, crystal chemical overviews of various mineral groups, the evolution of mineral species and their crystal structures, and descriptions of growth processes and the properties of the natural crystalline compounds.

Dr. Vladislav V. Gurzhiy
Guest Editor

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

minerals
crystallography
crystal chemistry
X-ray diffraction
crystal structures
crystal growth
mineral evolution

Published Papers (13 papers)

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24 pages, 6407 KiB

Open AccessArticle

Geochemical Characteristics of Nephrite from Chuncheon, South Korea: Implications for Geographic Origin Determination of Nephrite from Dolomite-Related Deposits

by Nan Li, Feng Bai, Qi Peng and Mengsong Liu

Crystals 2023, 13(10), 1468; https://doi.org/10.3390/cryst13101468 - 08 Oct 2023

Viewed by 944

Abstract

The Chuncheon nephrite deposit in South Korea is one of the major nephrite deposits in the world, but its origin has been rarely studied. This study explores the mineralogical and geochemical characteristics of the Chuncheon nephrite using a polarizing microscope, an electron microprobe, laser ablation, inductively coupled plasma mass spectrometry, and hydrogen–oxygen isotope analyses and compares them with dolomite-related nephrite worldwide. The main mineral of Chuncheon nephrite is tremolite, which has a felted blastic texture, secondary filling texture, and metasomatic pseudomorphic texture that nephrites from other regions do not have. Chuncheon nephrite is dolomite-related; the total content of rare earth elements is generally low, with highly variable positive and negative Eu anomalies and weak positive Ce anomalies; and the light rare earth elements are enriched. The Chuncheon nephrite formed in an anaerobic alkaline environment with a low degree of mineralization, and the hydrothermal fluids are predominantly meteoric water. Nephrite from different regions has different geochemical characteristics as well as different abundances of rare earth element contents. According to the content and range of elements, such as δCe, δEu, ΣREE, (La/Sm)N, and other rare earth elements, dolomite-type nephrite from different origins can be roughly distinguished. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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16 pages, 3065 KiB

Open AccessEditor’s ChoiceArticle

Hydrothermal Synthesis and Crystal Structure of Vesuvianite Compounds, Ca₁₉Al₁₃Si₁₈O₇₁(OH)₇ and Sr₁₉Fe₁₂Ge₁₉O₇₂(OH)₆

by Megan M. Smart, Cheryl A. Moore, Colin D. McMillen and Joseph W. Kolis

Crystals 2023, 13(8), 1257; https://doi.org/10.3390/cryst13081257 - 15 Aug 2023

Cited by 1 | Viewed by 739

Abstract

New compositions of synthetic vesuvianite were investigated using hydrothermal synthesis. High quality single crystals with the formula Ca₁₉Al₁₃Si₁₈O₇₁(OH)₇ (I) having the vesuvianite-type structure were crystallized during a high temperature hydrothermal growth reaction. Starting materials of Al₂O₃ and CaSiO₃ reacted at 670 °C and 2 kbar in 0.5 M aqueous alkali hydroxide mineralizer to form single crystals up to 0.25 mm per edge. Similar reactions employing SrO, Fe₂O₃, and GeO₂ reacting at 580 °C and 2 kbar in 6 M aqueous alkali hydroxide mineralizers led to the formation of the analogous Sr₁₉Fe₁₂Ge₁₉O₇₂(OH)₆ (II). These crystals were obtained in sizes up to 0.5 mm per edge. The structures of both compounds were refined in space group P4/nnc after careful evaluation of the diffraction data and subsequent test refinements. Elemental analysis indicated only the presence of Ca²⁺, Al³⁺, and Si⁴⁺ cations in I and only the presence of Sr²⁺, Fe³⁺, and Ge⁴⁺ cations in II, representing synthetic vesuvianite comprising the minimum number of unique cations. The use of larger cations than are typically found in natural vesuvianite, such as Sr²⁺, Fe³⁺, and Ge⁴⁺, resulted in an expanded crystalline lattice and extended the vesuvianite analogs to include an increasing variety of elements. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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14 pages, 5863 KiB

Open AccessArticle

A New Mineral Hanauerite, AgHgSI, and Common Crystal Chemical Features of Natural Mercury Sulphohalides

by Igor V. Pekov, Natalia V. Zubkova, Sergey N. Britvin, Atali A. Agakhanov, Yury S. Polekhovsky, Dmitry Y. Pushcharovsky, Gerhard Möhn, Joy Desor and Günter Blass

Crystals 2023, 13(8), 1218; https://doi.org/10.3390/cryst13081218 - 06 Aug 2023

Cited by 1 | Viewed by 942

Abstract

A new mineral, hanauerite, ideally AgHgSI, was found in the oxidation zone of Ag- and Hg-bearing ores at two old, abandoned mines in Rhineland-Palatinate, Germany. In a holotype specimen originating from the Schöne Aussicht Mine, Dernbach, Westerwald, it is associated with plumbogummite–hinsdalite series of minerals and goethite. In cotype from the Friedrichssegen Mine, Bad Ems, it is associated with perroudite, goethite, and quartz. At both localities, hanauerite occurs as a prismatic crystal up to 0.15 mm long and up to 0.02 mm thick. The mineral is yellow, transparent, with an adamantine lustre. It is brittle, and cleavage was not observed. The calculated density values are 6.671 and 6.575 g cm⁻³ for holotype and cotype, respectively. The empirical formulae calculated (from electron microprobe data) based on the sum of all atoms = 4 apfu are Ag_0.95Hg_1.00S_1.01(I_0.83Br_0.19Cl_0.03)_Σ1.05 for holotype and Ag_0.97Hg_0.97S_1.05(I_0.76Br_0.25)_Σ1.01 for cotype. Hanauerite is orthorhombic, space group Pmma; the unit cell parameters (from single-crystal X-ray diffraction data; holotype/cotype) are: a = 9.932(2)/9.9256(8), b = 4.6219(19)/4.6209(2), c = 9.891(4)/9.9006(4) Å, V = 454.0(3)/454.19(5) Å³, and Z = 4. The crystal structure was studied on single crystals extracted from both holotype and cotype specimens; R1 = 0.0416 (holotype) and =0.0544 (cotype). In hanauerite, Hg²⁺ cations centre strongly distorted octahedra with two short Hg–S bonds (Hg and S atoms build “crankshaft-type” chains) and four strongly elongated Hg–I bonds. The Hg-centred octahedra are connected via common edges and faces to form corrugated layers; Ag⁺ cations are located between these layers. Hanauerite is named in honour of the German mineral collector Dr. Alfred Hanauer (1912–1988). The common crystal chemical features of mercury sulphohalide minerals are discussed. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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12 pages, 4390 KiB

Open AccessArticle

Features of the Phase Formation of Cr/Mn/Fe/Co/Ni/Cu Codoped Bismuth Niobate Pyrochlore

by Nadezhda A. Zhuk, Boris A. Makeev, Maria G. Krzhizhanovskaya, Sergey V. Nekipelov, Danil V. Sivkov and Ksenia A. Badanina

Crystals 2023, 13(8), 1202; https://doi.org/10.3390/cryst13081202 - 02 Aug 2023

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Abstract

The phase formation process of Bi₂Cr_1/6Mn_1/6Fe_1/6Co_1/6Ni_1/6Cu_1/6Nb₂O_9+Δ containing 3d-ions of transition elements in equimolar quantities was studied in a wide temperature range (400–1050 °C). The complex oxide crystallizes in the structural type of pyrochlore (sp. gr. Fd-3m:2, a = 10.4937(2) Å). The investigation of the multi-element pyrochlore phase formation process showed that the synthesis goes through a series of successive stages, during which the transition from Bi-rich to Bi-depleted compounds takes place. The predecessor of the pyrochlore phase is bismuth orthorhombic modification orthoniobate (α-BiNbO₄) with an equimolar ratio of Bi(III)/Nb(V) ions. The pyrochlore phase is formed as a result of bismuth orthoniobate doping with transition element ions. The complex oxides Bi₁₄CrO₂₄, Bi₂₅FeO₄₀, BiNbO₄, and Bi₅Nb₃O₁₅ appeared as intermediate phases during the synthesis. The interaction between the initial oxide precursors is fixed at temperatures above 500 °C. The phase transition of α-Bi₂O₃ into β-Bi₂O₃ near 500 °C is observed. Varying the heat treatment duration at each synthesis step did not qualitatively change the phase composition of the sample but had an effect on the quantitative phase ratio. Phase-pure pyrochlore of the given composition by solid-phase synthesis method can be obtained at a temperature no lower than 1050 °C. Ceramics are characterized by low-porous dense microstructure with blurred outlines of grain boundaries. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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16 pages, 15230 KiB

Open AccessEditor’s ChoiceArticle

Different Cooling Histories of Ultrahigh-Temperature Granulites Revealed by Ti-in-Quartz: An Electron Microprobe Approach

by Di Zhang, Yi Chen, Qian Mao, Shujuan Jiao, Bin Su, Si Chen and Kyaing Sein

Crystals 2023, 13(7), 1116; https://doi.org/10.3390/cryst13071116 - 17 Jul 2023

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Abstract

The cooling history of granulite is crucial to understanding tectonic scenarios of the continental crust. Ti-in-quartz, a useful indicator of temperature, can decipher the thermal evolution of crustal rocks. Here we apply the Ti-in-quartz (TitaniQ) thermometer to ancient ultrahigh-temperature (UHT) granulites from the Khondalite Belt (KB) in the North China Craton (NCC) and young UHT granulites from the Mogok Metamorphic Belt (MMB), Myanmar. Ti content in quartz was analyzed using a highly precise method constructed in a CAMECA SXFive electron probe microanalyzer (EPMA). The granulites from the two localities show different quartz Ti contents with a constant deforced beam of 10 μm. Matrix quartz and quartz inclusions from the NCC granulites have 57–241 ppm and 65–229 ppm, respectively, corresponding to the TitaniQ temperatures of 653–810 °C and 666–807 °C. The calculated temperatures are significantly lower than the peak temperatures (850–1096 °C) obtained by other methods, due to the formation of abundant rutile exsolution rods in quartz during cooling. Thus, the low calculated temperatures for the NCC granulites reflect a cooling state near or after the exsolution of rutile from quartz, most likely caused by a slow cooling process. However, the matrix quartz from the MMB granulites is exsolution-free and records higher Ti contents of 207–260 ppm and higher metamorphic temperatures of 894–926 °C, close to the peak UHT conditions. This feature indicates that the MMB granulites underwent rapid cooling to overcome Ti loss from quartz. Therefore, determining the amount of Ti loss from quartz by diffusion can provide new insight into the cooling behavior of UHT granulites. When a large deforced beam of 50 μm was used to cover the rutile rods, the matrix quartz in the KB granulites could also yield the TitaniQ temperatures above 900 °C. Thus, our new data suggest that the TitaniQ thermometer could be useful for revealing UHT conditions. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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15 pages, 2342 KiB

Open AccessArticle

Atomic Arrangement, Hydrogen Bonding and Structural Complexity of Alunogen, Al₂(SO₄)₃·17H₂O, from Kamchatka Geothermal Field, Russia

by Elena S. Zhitova, Rezeda M. Sheveleva, Andrey A. Zolotarev and Anton A. Nuzhdaev

Crystals 2023, 13(6), 963; https://doi.org/10.3390/cryst13060963 - 16 Jun 2023

Cited by 1 | Viewed by 921

Abstract

Alunogen, Al₂(SO₄)₃·17H₂O, occurs as an efflorescent in acid mine drainage, low-temperature fumarolic or pseudofumarolic (such as with coal fires) terrestrial environments. It is considered to be one of the main Al-sulphates of Martian soils, demanding comprehensive crystal-chemical data of natural terrestrial samples. Structural studies of natural alunogen were carried out in the 1970s without localization of H atoms and have not been previously performed for samples from geothermal fields, despite the fact that these environments are considered to be proxies of the Martian conditions. The studied alunogen sample comes from Verkhne–Koshelevsky geothermal field (Koshelev volcano, Kamchatka, Russia). Its chemical formula is somewhat dehydrated, Al₂(SO₄)₃·15.8H₂O. The crystal structure was solved and refined to R₁ = 0.068 based on 5112 unique observed reflections with I > 2σ(I). Alunogen crystalizes in the P-1 space group, a = 7.4194(3), b = 26.9763(9), c = 6.0549(2) Å, α = 90.043(3), β = 97.703(3), γ = 91.673(3) °, V = 1200.41(7) Å³, Z = 2. The crystal structure consists of isolated SO₄ tetrahedra, Al(H₂O)₆ octahedra and H₂O molecules connected by hydrogen bonds. The structure refinement includes Al, S and O positions that are similar to previous structure determinations and thirty-four H positions localized for the natural sample first. The study also shows the absence of isomorphic substitutions in the composition of alunogen despite the iron-enriched environment of mineral crystallization. The variability of the alunogen crystal structure is reflected in the number of the “zeolite” H₂O molecules and their splitting. The structural complexity of alunogen and its modifications ranges from 333–346 bits/cell for models with non-localized H atoms to 783–828 bits/cell for models with localized H atoms. The higher values correspond to the higher hydration state of alunogen. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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13 pages, 3195 KiB

Open AccessArticle

The Crystal Structure of Mg–Al–CO₃ Layered Double Hydroxide

by Elena S. Zhitova, Rezeda M. Sheveleva, Andrey A. Zolotarev and Sergey V. Krivovichev

Crystals 2023, 13(5), 839; https://doi.org/10.3390/cryst13050839 - 19 May 2023

Cited by 1 | Viewed by 1510

Abstract

The crystal structure of quintinite, Mg₄Al₂(OH)₁₂(CO₃)·3H₂O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to a

\sqrt{3}

\sqrt{3}

superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms; the average <Mg–O> and <Al–O> bond distances are in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions), and consist of disordered (CO₃)²⁻ groups and (H₂O)⁰ molecules. The samples from Jacupiranga can be identified as quintinite-2T, which is the second finding of this polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010), indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d_00n-value) of ~7.56 Å, which is steady among natural specimens from various findings worldwide. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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18 pages, 3548 KiB

Open AccessEditor’s ChoiceArticle

Carbonate Minerals’ Precipitation in the Presence of Background Electrolytes: Sr, Cs, and Li with Different Transporting Anions

by Pedro Marin-Troya, Carlos Espinosa, Luis Monasterio-Guillot and Pedro Alvarez-Lloret

Crystals 2023, 13(5), 796; https://doi.org/10.3390/cryst13050796 - 10 May 2023

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Abstract

Carbonate minerals are largely associated with many geological and biological environments as well as several industrial and technological processes. The crystalline characteristics of these mineral phases can be modified by background salts present in the solution due to the effect of different electrolytes on the dynamics of ion-water interactions and ionic strength during precipitation. In the current research, we studied the effect of the presence of several electrolytes (i.e., Cs, Li, and Sr), combined with chloride and carbonate as transporting anions, on the growth and mineral evolution processes of carbonate precipitation in solution. The electrolyte composition during the reaction (experimental times from 24 h up to 30 days) determined the formation of specific calcium carbonate polymorphs. The Li presence induced the formation of vaterite which was progressively transformed into calcite during the reaction time, while Cs stabilized the calcite formation. The Sr presence in the system caused the precipitation of strontianite with modifications in its cell parameters and the structural arrangement of the carbonate molecular group. During the mineral evolution considering chloride and carbonate experimental set-ups, several compositional and cell parameters/crystallinity variations of the carbonated phases were also observed. A better understanding of the relationship between the compositional properties of the aqueous solvent and the crystallization mechanisms can contribute to a deeper comprehension of the mineral precipitation and transformation in different multicomponent solutions that occur in natural environments and in controlled synthesis processes. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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12 pages, 2979 KiB

Open AccessArticle

Crystal Structures of CuCl₂·2H₂O (Eriochalcite) and NiCl₂∙6H₂O (Nickelbischofite) at Low Temperature: Full Refinement of Hydrogen Atoms Using Non-Spherical Atomic Scattering Factors

by René T. Boeré

Crystals 2023, 13(2), 293; https://doi.org/10.3390/cryst13020293 - 09 Feb 2023

Cited by 6 | Viewed by 2360

Abstract

New structure determinations of CuCl₂∙2H₂O and NiCl₂∙6H₂O are reported from 100 K X-ray diffraction experiments using both Mo Kα and Cu Kα radiation. Combined density functional theory (ORCA) and non-spherical atomic scattering factor (NoSpherA2) computations enabled Hirshfeld atom refinements (HAR) using custom atom scattering factors based on accurately polarized atom electron densities. The water hydrogen atoms could be positionally refined resulting in distinctly longer O–H bond lengths than those reported from previous X-ray diffraction experiments, but in good agreement with legacy neutron diffraction studies. Anisotropic displacement factors were employed, for the first time in these compounds by any technique. The outcomes from using the different X-ray sources with this new HAR method are compared, and the precision of the H-atom refinements evaluated where possible. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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13 pages, 16564 KiB

Open AccessArticle

Type and Sources of Salt Efflorescence in Painted Stone Carvings from Pujiang Museum, Sichuan, China

by Quanshuai Song, Jianrui Zha, Yulong Bai, Long Chen, Yao Zhang and Hong Guo

Crystals 2023, 13(2), 273; https://doi.org/10.3390/cryst13020273 - 04 Feb 2023

Cited by 3 | Viewed by 1343

Abstract

Painted stone carvings from Pujiang Museum in Chengdu were excavated from the Ming tombs near to Chengdu Metro Line 7. The Ming burial sites were the eunuch graves of the Shu King, and their tomb was constructed mostly of stone and decorated with paintings and carvings on its surface, which are of great value. However, during their burial, these painted stone carvings suffered significant salt damage. In this research, we performed optical microscope (OM) analysis, Raman spectra (RAM), ion chromatography (IC) analysis, X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRD), and petrographic microscopy (PM) to clarify the salt composition and influence. According to the results, the majority of the salt on the painted layer is CaSO₄·2H₂O. Before excavation, interaction between acid rain, soil, and groundwater created salt efflorescence on the paint layer’s surface. The deterioration of the paint layer caused by gypsum was divided into two stages: before excavation and during in situ preservation. This research provides a foundation for the removal and prevention of salt efflorescence. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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14 pages, 3873 KiB

Open AccessArticle

The Structural Characteristics and Chemical Composition of Serpentine Jade Weathering Rinds: Implications for the Formation Process

by Shanna Xue, Mingyue He, Mei Yang and Shaokun Wu

Crystals 2023, 13(2), 239; https://doi.org/10.3390/cryst13020239 - 30 Jan 2023

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Abstract

Weathering rind retains the greatest extent of the mineralogical and chemical composition information of the original mineral. Recently, we found some brownish-yellow or khaki serpentine jade weathering rinds with a thickness of 0.2–0.6 cm in Ji’an. The purpose of this paper is to explore differences in structural characteristics and chemical composition between weathering rinds and unweathered cores and summarize the formation of weathering rinds. In terms of structural characteristics, weathering rinds have smaller a₀, b₀, β values than unweathered cores; the specific surface area is 13.3987 m²/g; the pore volume is 0.0314 cm³/g; and the pore size distribution is characterized as more mesoporous (2–10 nm). The weathering rind shows partial dissolution of serpentine grains, increased porosity, and loosening structure. In terms of chemical composition, the weathering rind is characterized by the decrease of some serpentine major elements (Si, Mg, and Fe) and the increase of some impurity elements (Al, Ca, K, Na, and Cl). The weathering rind is the result of further alteration of serpentine jade, accompanied by the reduction of the Fe³⁺/Fe²⁺ ratio and the generation of the clay mineral (chlorite). In addition, it was also found that Ji’an serpentine jade belongs to Mg-bearing carbonate rock genesis, which are derived from marine deposits. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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24 pages, 33932 KiB

Open AccessArticle

Jedi Spinel from Man Sin, Myanmar: Color, Inclusion, and Chemical Features

by Yujie Gao, Mingyue He, Xueying Sun, Cuiling Zhen, Huihuang Li, Xiaotao Wei and Yizhi Zhao

Crystals 2023, 13(1), 103; https://doi.org/10.3390/cryst13010103 - 05 Jan 2023

Cited by 1 | Viewed by 4808

Abstract

In the present study, we collected and investigated spinels from the Man Sin deposit in Myanmar using standard gemological testing, microscopic observation, EDXRF, and Raman spectrometry. The color observation was performed under various lighting conditions to show color differences. A very high Cr/Fe ratio is linked with exceptionally strong red fluorescence. Microscopic observation and Raman spectroscopy identified mineral inclusions of colorless phlogopite, molybdenite, hauerite, native sulfur, and calcite. Man Sin spinels are typical Fe– and Zn–poor spinels. Binary and ternary diagrams were used to discriminate each deposit (i.e., Man Sin, Mogok, and Namya in Myanmar) with high reliability. Jedi spinel fever in the Asian market, due to their unique neon color appearance and exceptionally strong fluorescence, is also discussed. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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27 pages, 18236 KiB

Open AccessReview

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

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

Crystals 2024, 14(1), 15; https://doi.org/10.3390/cryst14010015 - 23 Dec 2023

Viewed by 739

Abstract

This paper reviews not the largest, but at the same time quite an interesting, group of natural and synthetic uranyl molybdate compounds. Nowadays, nine minerals of U and Mo are known, but the crystal structures have only been reported for five of them. Almost an order of magnitude more (69) synthetic compounds are known. A significant discrepancy in the topological types for natural and synthetic phases is shown, which is most likely due to elevated temperatures of laboratory experiments (up to 1000 °C), while natural phases apparently grow at significantly lower temperatures. At the same time, the prevalence of dense topologies (with edge-sharing interpolyhedral linkage) among natural phases can be noted, which is fully consistent with other recently considered mineral groups. Uranyl molybdates demonstrate several similarities with compounds of other U-bearing groups; however, even topological matches do not lead to the appearance of completely isotypic compounds. Structural complexity calculations confirm, in general, crystal chemical observations. Considering the prevalence of dense structures in which coordination polyhedra of uranium and molybdenum are connected through common edges as well as framework architectures, one can expect a less significant influence of interlayer species on the formation of the crystal structure than the main U-bearing complexes. The more structural complexity of the uranyl molybdate units, the more complex of the entire crystal structure is. In addition, there is a tendency for complexity to increase with increasing density of the complex; the simplest structures are vertex-shared, while the complexity increases with the appearance of common edges. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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