Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 17685

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Institut für Mineralogie und Kristallographie, Universität Wien, Althanstrasse 14, A-1090 Wien, Austria
Interests: hydrothermal/ionothermal synthesis; crystal chemistry of mineral-like oxo-salts; environmental mineralogy; structural crystallography; sulfidic mine wastes

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Department of Crystallography and Crystal Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
Interests: XRD analysis; crystal structures; minerals; new structure types; crystal chemistry
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Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8/a, HR-31000 Osijek, Croatia
Interests: solid state chemistry; materials chemistry; condensed matter physics; magnetic properties; structure–property relationship; bandstructure calculation; sol-gel synthesis; crystal structure determination; three-way catalysts; functional materials; nanomaterials; perovskites; multiferroicity; metal–organic frameworks
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is a tribute to the recently deceased Emeritus Professor of Mineralogy and Crystallography, Dr. Ekkehart Tillmanns, who has left a special legacy in the field of mineralogical crystallography and mineral synthesis. The Special Issue plans to include a representative group of papers in the field of synthesis and structural crystallography of mineral-related oxo-salts.

Within the last twenty-five years, there has been ever-increasing activity in the field of systematic treatment of various classes of mineral-like oxo-salts. Some of them (e.g., silicates, zeolites, vanadates, phosphates, copper oxo-salts, REE oxo-compounds, etc.) are used in a wide variety of technical applications, and some of them attract attention because of their environmental importance (e.g., arsenates, carbonates and sulphates). Their technical use and/or environmental stability is based on their special physical and chemical behavior, which is intrinsically dependent on their crystal structure.

A thorough investigation of the mineral-related chemical systems leads to a detailed understanding of which topologies and connectivities are likely to form under which conditions (e.g., temperature, pH, ratios of ionic radii, etc.), a knowledge that could also be applied to the various groups of different oxo-salts.

Therefore, the idea behind this Special Issue is to identify the most successful synthesis approaches applied to the preparation of the numerous classes of mineral-like oxo-salts. Besides the development of the synthesis techniques for oxo-salt synthesis, an additional focus of this Special Issue will also be the establishing of the correlation between the preparation conditions and crystal structure on the one hand, and the resulting properties and/or environmental stability on the other.

We look forward to receiving your contributions in the form of communications, full articles, or review papers.

Dr. Tamara Đorđević
Dr. Natalia V. Zubkova
Prof. Dr. Igor Djerdj
Guest Editors

Manuscript Submission Information

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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. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydrothermal synthesis
  • solvothermal synthesis
  • sol-gel route
  • flux growth
  • arsenates
  • carbonates
  • phosphates
  • sulphates
  • silicates
  • vanadates

Published Papers (10 papers)

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Research

Jump to: Review

8 pages, 905 KiB  
Article
Location of Carbonate Ions in Metal-Doped Carbonated Hydroxylapatites
by Claude H. Yoder and Julia T. Goodman
Minerals 2023, 13(10), 1272; https://doi.org/10.3390/min13101272 - 29 Sep 2023
Viewed by 504
Abstract
The environment model for the description of the location of carbonate ions in apatites predicts that approximately half of the carbonate occupies the apatite channel. This model relies on the influence of entities surrounding the carbonate on its IR spectrum and can be [...] Read more.
The environment model for the description of the location of carbonate ions in apatites predicts that approximately half of the carbonate occupies the apatite channel. This model relies on the influence of entities surrounding the carbonate on its IR spectrum and can be used to determine how various substituents affect the location and structure of that ion. Careful deconvolution (peak-fitting) of the asymmetric carbonate IR region was used to determine the percentage of A-type (channel) ions, A′-type (channel with either a Ca2+ vacancy or substitution of Na+ for Ca2+) ions, and B-type (substitution for phosphate) ions. In our previous applications of this model, we have looked at the effect of alkali metal ions, such as sodium, lithium, and potassium, the ammonium ion, and the rare earth europium ion. In the present work, we explore the incorporation of the first-row transition metal ions and find that they have little effect on the location of the carbonate ion. Like the un-substituted carbonated apatite, these apatites contain about half of the carbonate in the channel, at least in derivatives that contain up to half a mole of the metal ion per mole of apatite. Attempts to incorporate greater amounts of metal ions by aqueous ion-combination reactions generally lead to lower-resolution XRD patterns and IR spectra that produce greater uncertainties in the peak-fitting modeling. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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13 pages, 2024 KiB  
Article
The Crystal Structure and Crystal Chemistry of Mineral-like Cd5(VO4)2(OH)4, a Novel Isomorph of Arsenoclasite and Gatehouseite
by Ljiljana Karanović and Tamara Ðorđević
Minerals 2022, 12(12), 1601; https://doi.org/10.3390/min12121601 - 12 Dec 2022
Cited by 1 | Viewed by 1258
Abstract
The pentacadmium bis(vanadate(V)) tetrahydroxide Cd5(VO4)2(OH)4 was synthesized under hydrothermal conditions, and its crystal structure was determined with single-crystal X-ray diffraction. The investigated compound is the second known compound next to Cd(VO3)2·4H2 [...] Read more.
The pentacadmium bis(vanadate(V)) tetrahydroxide Cd5(VO4)2(OH)4 was synthesized under hydrothermal conditions, and its crystal structure was determined with single-crystal X-ray diffraction. The investigated compound is the second known compound next to Cd(VO3)2·4H2O synthesized in the CdO–V2O5–H2O system and crystallizes isotypically to the minerals gatehouseite, Mn5(PO4)2(OH)4, and its As analog arsenoclasite, Mn5(AsO4)2(OH)4. Its symmetry is orthorhombic, with a space group of P212121 and unit cell parameters of a = 19.011(4), b = 6.0133(12), c = 9.5411(19) Å, V = 1090.7(4) Å3, and Z = 4. The structure consists of double ribbons of M(O,OH)6-octahedra (M = Cd2, Cd3, Cd4) extending along [010] interconnected by edge- and corner-shared M(O,OH)6-octahedra (M = Cd1, Cd5) and discrete, slightly distorted VO4 tetrahedra, which form double chains of coupled polyhedra [V1O4–Cd5O4(OH)2–Cd1O5(OH)–V2O4]n running along the same direction. The interesting feature is the existence of V–Cd distances (3.0934(7) and 3.1081(7) Å for V1–Cd5 and V2–Cd1, respectively), which are shorter than the sum of the van der Waals radii of 3.71 Å. The V1–V2 distances of 4.1214(9) Å are also shorter than the sum of the van der Waals radii of 4.26 Å. The O–H···O hydrogen bonds additionally link the two subunits, ribbons, and chains into a three-dimensional structure. Raman spectra confirmed the presence of the hydrogen bonds and mutually isolated VO4 groups. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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14 pages, 2766 KiB  
Article
Mixed Valanced V3+,V2+ Phosphate Na7V4(PO4)6: A Structural Analogue of Mineral Yurmarinite
by Galina Kiriukhina, Valentina Nesterova, Olga Yakubovich, Anatoly Volkov, Olga Dimitrova, Alexander Trigub and Konstantin Lyssenko
Minerals 2022, 12(12), 1517; https://doi.org/10.3390/min12121517 - 27 Nov 2022
Viewed by 1378
Abstract
Two sodium vanadium phosphates, synthetic analogues of the minerals kosnarite, Na3V2(PO4)3, and yurmarinite, Na7V4(PO4)6, were obtained by hydrothermal synthesis simulating a natural hydrothermal solution. While the Na [...] Read more.
Two sodium vanadium phosphates, synthetic analogues of the minerals kosnarite, Na3V2(PO4)3, and yurmarinite, Na7V4(PO4)6, were obtained by hydrothermal synthesis simulating a natural hydrothermal solution. While the Na3V2(PO4)3 phase belongs to the NASICON family and is well-known for its high-ionic conductivity, the new Na7V4(PO4)6 compound is a rare case of V2+-containing oxosalts, which are hard to prepare due to their instability in air. Here we report the crystal structure of heterovalent vanadium phosphate studied by single crystal X-ray diffraction, XANES spectroscopy, and topological ion migration modelling. A discussion of divalent vanadium compounds of both natural and synthetic origin is also given, with a review of the methods for their synthesis and a comparative analysis of V–O bond lengths. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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17 pages, 1217 KiB  
Article
Temperature-Induced Phase Transition in a Feldspar-Related Compound BaZn2As2O8∙H2O
by Liudmila A. Gorelova, Oleg S. Vereshchagin, Vladimir N. Bocharov, Dmitrii V. Pankin and Tamara Đorđević
Minerals 2022, 12(10), 1262; https://doi.org/10.3390/min12101262 - 06 Oct 2022
Cited by 2 | Viewed by 1334
Abstract
The high-temperature (HT) behavior of BaAs2Zn2O8∙H2O was studied by in situ single-crystal X-ray diffraction (SCXRD) and hot stage Raman spectroscopy (HTRS) up to dehydration and the associated phase transition. During heating, the studied compound undergoes [...] Read more.
The high-temperature (HT) behavior of BaAs2Zn2O8∙H2O was studied by in situ single-crystal X-ray diffraction (SCXRD) and hot stage Raman spectroscopy (HTRS) up to dehydration and the associated phase transition. During heating, the studied compound undergoes the dehydration process with the formation of BaAs2Zn2O8, which is stable up to at least 525 °C. The evolution of the fourteen main Raman bands was traced during heating. The abrupt shift of all Raman bands in the 70–1100 cm−1 spectral region was detected at 150 °C, whereas in the spectral region 3000–3600 cm−1 all the bands disappeared, which confirms the dehydration process of BaAs2Zn2O8∙H2O. The transition from BaAs2Zn2O8∙H2O to BaAs2Zn2O8 is accompanied by symmetry increasing from P21 to P21/c with the preservation of the framework topology. Depending on the research method, the temperature of the phase transition is 150 °C (HTRS) or 300 °C (HT SCXRD). According to the HT SCXRD data, in the temperature range 25–300 °C the studied compound demonstrates anisotropic thermal expansion (αmaxmin = 9.4), which is explained by flexible crankshaft chains of TO4 (T = As, Zn) tetrahedra. Additionally, we discussed some crystal-chemical aspects of minerals with both (ZnOn) and (AsOm) polyhedra (n = 4, 5, 6; m = 3, 4) as main structural units. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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11 pages, 5369 KiB  
Article
Na-Alternative to Tinsleyite Obtained under Hydrothermal Conditions: Crystal Structure and Comparative Crystal Chemistry
by Olga Yakubovich, Galina Kiriukhina, Polina Verchenko, Sergey Simonov, Anatoly Volkov and Olga Dimitrova
Minerals 2022, 12(5), 542; https://doi.org/10.3390/min12050542 - 27 Apr 2022
Cited by 1 | Viewed by 1450
Abstract
The synthesis and characterization of a new aluminophosphate, Na2Al2O(PO4)2·0.12H2O obtained as single crystals, is reported. Centrosymmetric tetramers built from AlO5 polyhedra sharing edges and vertices, represent the distinguished feature of the compound. [...] Read more.
The synthesis and characterization of a new aluminophosphate, Na2Al2O(PO4)2·0.12H2O obtained as single crystals, is reported. Centrosymmetric tetramers built from AlO5 polyhedra sharing edges and vertices, represent the distinguished feature of the compound. These tetrameric units of AlO5 bipyramids are cross-linked by PO4 tetrahedra to form two-periodic slabs alternating with Na+ ions and a small amount of H2O molecules. The Na2Al2O(PO4)2·0.12H2O with an original crystal architecture is chemically and structurally related to the mineral tinsleyite, KAl2(PO4)2(OH)·2H2O. Similar clusters of Al-centered polyhedra are essential building blocks of both monoclinic structures. The main difference between them consists of the type of the Al coordination by O atoms: in tinsleyite, the clusters are designed from AlO4(OH)2 and AlO4(OH)(H2O) octahedra. In both cases, alkali Na or K atoms significantly distinct in size, act as structure regulating agents, determining the character of the developing crystal architecture. The flexibility of aluminophosphate constructions allows them to self-organize around structure-forming Na+ or K+ ions into anionic layers in Na2Al2O(PO4)2·0.12H2O or a framework (tinsleyite). The synthesis of sodium aluminophosphate under mild hydrothermal conditions and the topological resemblance of its structure with that of the mineral tinsleyite suggest a high probability of a mineral equivalent of the Na2Al2O(PO4)2·0.12H2O in nature. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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14 pages, 3001 KiB  
Article
Water in the Alluaudite Type-Compounds: Synthesis, Crystal Structure and Magnetic Properties of Co3(AsO4)0.5+x(HAsO4)2−x(H2AsO4)0.5+x[(H,□)0.5(H2O,H3O)0.5]2x+
by Tamara Đorđević, Ljiljana Karanović, Marko Jagodič and Zvonko Jagličić
Minerals 2021, 11(12), 1372; https://doi.org/10.3390/min11121372 - 04 Dec 2021
Viewed by 2065
Abstract
In this study, a new cobalt arsenate belonging to the alluaudite supergroup compounds with the general formula of Co3(AsO4)0.5+x(HAsO4)2−x(H2AsO4)0.5+x[(H,□)0.5(H2O,H3O)0.5] [...] Read more.
In this study, a new cobalt arsenate belonging to the alluaudite supergroup compounds with the general formula of Co3(AsO4)0.5+x(HAsO4)2−x(H2AsO4)0.5+x[(H,□)0.5(H2O,H3O)0.5]2x+ (denoted as CoAsAllu) was synthesized under hydrothermal conditions. Its crystal structure was determined by a room-temperature single-crystal X-ray diffraction analysis: space group C2/c, a = 11.6978(8), b = 12.5713(7), c = 6.7705(5) Å, β = 113.255(5)°, V = 914.76(11) Å3, Z = 2 for As6H8Co6O25. It represents a new member of alluaudite-like protonated arsenates and the first alluaudite-like phase showing both protonation of the tetrahedral site and presence of the H2O molecules in the channels. In the asymmetric unit of CoAsAllu, one of the two Co, one of the two As and one of the seven O atoms lie at 4e special positions (site symmetry 2). The crystal structure consists of the infinite edge-shared CoO6 octahedra chains, running parallel to the [101¯] direction. The curved chains are interconnected by [(As1O4)0.5(H2As1O4)0.5]2− and [HAs2O4]2− tetrahedra forming a heteropolyhedral 3D open framework with two types of parallel channels. Both channels run along the c-axis and are located at the positions (1/2, 0, z) and (0, 0, z), respectively. The H2 and H4 hydrogen atoms of O2H2 and O4H4 hydroxyl groups are situated in channel 1, while the uncoordinated water molecule H2O7 at half-occupied 4e special positions and hydrogen atoms of O6H6 hydroxyl group were found in channel 2. The results of the magnetic investigations confirm the quasi one-dimensional structure of divalent cobalt ions. They are antiferromagnetically coupled with the intrachain interaction parameter of J ≈ −8 cm−1 and interchain parameter of J’ ≈ −2 cm−1 that become effective below the Néel temperature of 3.4 K. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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13 pages, 5601 KiB  
Article
Interzeolitic Transformation of Clinoptilolite into GIS and LTA Zeolite
by Renata C. F. de Lima, Daniele da Silva Oliveira and Sibele B. C. Pergher
Minerals 2021, 11(12), 1313; https://doi.org/10.3390/min11121313 - 25 Nov 2021
Cited by 5 | Viewed by 2371
Abstract
A natural clinoptilolite zeolite was transformed into other zeolites of greater industrial interest, such as zeolites with GIS and LTA structures. The synthesis conditions were studied, and the interzeolitic transformation was characterized by X-ray diffraction (XRD), X-ray fluorescence (FRX), Fourier transform infrared spectroscopy [...] Read more.
A natural clinoptilolite zeolite was transformed into other zeolites of greater industrial interest, such as zeolites with GIS and LTA structures. The synthesis conditions were studied, and the interzeolitic transformation was characterized by X-ray diffraction (XRD), X-ray fluorescence (FRX), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). From the results, it was possible to observe that the GIS and LTA zeolites were successfully synthesized. Furthermore, the results revealed that a synthesis time of 4 days was enough to obtain the GIS structure, and 4 h was sufficient to obtain LTA. The interzeolitic transformation can be explained by the RBU (Ring Building Unit) approach using C4 units from the HEU topology. The use of clinoptilolite in the synthesis of other zeolites is an innovative, economically viable, and environmentally sustainable process that exploits a material that exists in large quantities and is still little explored by industry. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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14 pages, 2754 KiB  
Article
Phase Evolution from Volborthite, Cu3(V2O7)(OH)2·2H2O, upon Heat Treatment
by Rezeda M. Ismagilova, Elena S. Zhitova, Sergey V. Krivovichev, Anastasia V. Sergeeva, Anton A. Nuzhdaev, Leonid P. Anikin, Mariya G. Krzhizhanovskaya, Maria A. Nazarova, Anastasia N. Kupchinenko, Andrey A. Zolotarev, Anton V. Kutyrev, Daria S. Bukhanova, Ruslan A. Kuznetsov and Dmitry A. Khanin
Minerals 2021, 11(12), 1312; https://doi.org/10.3390/min11121312 - 24 Nov 2021
Cited by 1 | Viewed by 1814
Abstract
In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V [...] Read more.
In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V site. The evolution of Cu-V minerals during in situ heating is as follows: volborthite Cu3(V2O7)(OH)2·2H2O (30–230 °C) → X-ray amorphous phase (230–290 °C) → ziesite β-Cu2(V2O7) (290–430 °C) → ziesite + pseudolyonsite α-Cu3(VO4)2 + mcbirneyite β-Cu3(VO4)2 (430–510 °C) → mcbirneyite (510–750 °C). This trend of mineral evolution agrees with the thermal analytical data. These phases also dominate in all experiments with an ex situ annealing. However, the phase compositions of the samples annealed ex situ are more complex: fingerite Cu11(VO4)6O2 occurs in the samples annealed at ~250 and ~480 °C and quickly or slowly cooled to room temperature, and in the sample annealed at ~850 °C with fast cooling. At the same time, blossite and stoiberite have been found in the samples annealed at ~480–780 and ~780–850 °C, respectively, and slowly cooled to room temperature. There is a trend of decreasing crystal structure complexity in the raw phases obtained by the in situ heating with the increasing temperature: volborthite → ziesite → mcbirneyite (except of pseudolyonsite). Another tendency is that the longer the sample is cooled, the more complex the crystal structure that is formed, with the exception of blossite, most probably because blossite and ziesite are polymorphs with identical crystal structure complexities. The high complexity of fingerite and stoiberite, as well as their distinction by Cu:V ratio, may explain the uncertain conditions of their formation. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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16 pages, 2620 KiB  
Article
Crystal Structure Refinements of the Lead(II) Oxoarsenates(V) Pb2As2O7, Pb(H2AsO4)2, Pb5(AsO4)3OH and NaPb4(AsO4)3 from Single-Crystal X-ray Data
by Matthias Weil
Minerals 2021, 11(11), 1156; https://doi.org/10.3390/min11111156 - 20 Oct 2021
Cited by 1 | Viewed by 1916
Abstract
Single-crystals of lead(II) oxoarsenates(V) were grown from the melt (Pb2As2O7), from solution (Pb(H2AsO4)2 and Pb5(AsO4)3OH), and under hydrothermal conditions (NaPb4(AsO4)3). [...] Read more.
Single-crystals of lead(II) oxoarsenates(V) were grown from the melt (Pb2As2O7), from solution (Pb(H2AsO4)2 and Pb5(AsO4)3OH), and under hydrothermal conditions (NaPb4(AsO4)3). Crystal structure refinements from single-crystal X-ray diffraction data revealed isotypism for both Pb2As2O7 and Pb(H2AsO4)2 with the corresponding barium and phosphate phases. A quantitative comparison of the crystal structures showed a high similarity for the isotypic M2X2O7 structures (M = Pb, Ba; X = As, P), whereas for the M(H2XO4)2 structures only the pair Pb(H2AsO4)2 and Pb(H2PO4)2 is similar, but not Ba(H2AsO4)2. Pb5(AsO4)3OH adopts the apatite structure type in space group P63/m, with the hydroxyl group disordered around Wyckoff position 2 b (0, 0, 0) in the channels of the structure. NaPb4(AsO4)3 represents a lacunar apatite with two of the three metal positions occupationally disordered by Pb and Na. In contrast to a previous X-ray powder study of NaPb4(AsO4)3 that reported an apatite-type structure in space group P63/m, the current single-crystal data clearly revealed a symmetry reduction to space group P3¯. Hence, NaPb4(AsO4)3 is the first lacunar apatite that comprises only tetrahedral anions and adopts the belovite structure type. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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Review

Jump to: Research

22 pages, 6609 KiB  
Review
The Gel Growth Technique—A Neglected Yet Effective Tool to Prepare Crystals of Oxysalts and Supergene Minerals
by Dominik Talla and Andreas Wagner
Minerals 2022, 12(5), 645; https://doi.org/10.3390/min12050645 - 20 May 2022
Cited by 2 | Viewed by 1957
Abstract
The technique of crystal growth in gels has nowadays become somewhat neglected in the scope of earth sciences, to the disadvantage of the experimental mineralogist. Even preparing an inorganic silica gel can prove a challenge to many, let alone successfully configure the entire [...] Read more.
The technique of crystal growth in gels has nowadays become somewhat neglected in the scope of earth sciences, to the disadvantage of the experimental mineralogist. Even preparing an inorganic silica gel can prove a challenge to many, let alone successfully configure the entire experiment. Based not only on previous literature but also on our extensive experience, crystals of many substances, including supergene minerals as reference standards, can be successfully grown in gel, aiding in accomplishing various research goals in earth sciences. Instead of providing the reader with an overwhelming compendium of historical information and theoretical knowledge of the subject which can be found elsewhere, we presented herein a comprehensive, practically oriented guide to the understanding and successful use of the technique of crystal growth in gels, mentioning, in addition to the general principle, the numerous pitfalls which we encountered during our own use of the method, and the ways to overcome them. Despite that the procedure is nowadays used mainly for the laboratory synthesis of organic or metal-organic compounds, we believe it to be a valuable asset to any mineralogist, and often, the only way to obtain inorganic reference material of a particular mineral of interest. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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