G. Diego Gatta, Silvia C. Capelli, Davide Comboni, Enrico Cannaò
{"title":"On the crystal-chemistry of inderite, Mg[B3O3(OH)5](H2O)4·H2O","authors":"G. Diego Gatta, Silvia C. Capelli, Davide Comboni, Enrico Cannaò","doi":"10.1007/s00269-024-01281-w","DOIUrl":null,"url":null,"abstract":"<div><p>The crystal chemistry of inderite, a hydrous borate with known ideal formula MgB<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub>·5H<sub>2</sub>O from the Kramer deposit, was re-investigated by electron probe micro-analysis in wavelength dispersive mode, laser ablation-(multi collector-)inductively coupled plasma-mass spectrometry and single-crystal neutron diffraction. The chemical data prove that the real composition of the investigated inderite is substantially identical to the ideal one, with insignificant content of potential isomorphic substituents, so that, excluding B, inderite does not contain any other industrially-relevant element (e.g., Li concentration is lower than 2.5 wt ppm, Be or REE lower than 0.1 wt ppm). The average δ<sup>11</sup>B<sub>NIST951</sub> value of <i>ca.</i> − 7 ‰ lies within the range of values in which the source of boron is ascribable to terrestrial reservoirs (e.g., hydrothermal brines), rather than to marine ones. Neutron structure refinements, at both 280 and 10 K, confirm that the building units of the structure of inderite consist of: two BO<sub>2</sub>(OH)<sub>2</sub> tetrahedra (B-ion in <i>sp</i><sup>3</sup> electronic configuration) and one BO<sub>2</sub>(OH) triangle (B-ion in <i>sp</i><sup>2</sup> electronic configuration), linked by corner-sharing to form a (soroborate) B<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub> ring, and a Mg-octahedron Mg(OH)<sub>2</sub>(OH<sub>2</sub>)<sub>4</sub>. The B<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub> ring and the Mg-octahedron are connected, by corner-sharing, to form an isolated Mg(H<sub>2</sub>O)<sub>4</sub>B<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub> (molecular) cluster. The tri-dimensional edifice of inderite is therefore built by heteropolyhedral Mg(H<sub>2</sub>O)<sub>4</sub>B<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub> clusters mutually connected by H-bonds, mediated by the zeolitic (“interstitial”) H<sub>2</sub>O molecules lying between the clusters, so that the correct form of the chemical formula of inderite is Mg[B<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub>](H<sub>2</sub>O)<sub>4</sub>·H<sub>2</sub>O, rather than MgB<sub>3</sub>O<sub>3</sub>(OH)<sub>5</sub>·5H<sub>2</sub>O. All the thirteen independent oxygen sites of the structure are involved in H-bonding, as donors or as acceptors. This confirms the pervasive nature and the important role played by the H-bonding network on the structural stability of inderite. The differences between the crystal structure of the two dimorphs inderite and kurnakovite are discussed.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-024-01281-w.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-024-01281-w","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The crystal chemistry of inderite, a hydrous borate with known ideal formula MgB3O3(OH)5·5H2O from the Kramer deposit, was re-investigated by electron probe micro-analysis in wavelength dispersive mode, laser ablation-(multi collector-)inductively coupled plasma-mass spectrometry and single-crystal neutron diffraction. The chemical data prove that the real composition of the investigated inderite is substantially identical to the ideal one, with insignificant content of potential isomorphic substituents, so that, excluding B, inderite does not contain any other industrially-relevant element (e.g., Li concentration is lower than 2.5 wt ppm, Be or REE lower than 0.1 wt ppm). The average δ11BNIST951 value of ca. − 7 ‰ lies within the range of values in which the source of boron is ascribable to terrestrial reservoirs (e.g., hydrothermal brines), rather than to marine ones. Neutron structure refinements, at both 280 and 10 K, confirm that the building units of the structure of inderite consist of: two BO2(OH)2 tetrahedra (B-ion in sp3 electronic configuration) and one BO2(OH) triangle (B-ion in sp2 electronic configuration), linked by corner-sharing to form a (soroborate) B3O3(OH)5 ring, and a Mg-octahedron Mg(OH)2(OH2)4. The B3O3(OH)5 ring and the Mg-octahedron are connected, by corner-sharing, to form an isolated Mg(H2O)4B3O3(OH)5 (molecular) cluster. The tri-dimensional edifice of inderite is therefore built by heteropolyhedral Mg(H2O)4B3O3(OH)5 clusters mutually connected by H-bonds, mediated by the zeolitic (“interstitial”) H2O molecules lying between the clusters, so that the correct form of the chemical formula of inderite is Mg[B3O3(OH)5](H2O)4·H2O, rather than MgB3O3(OH)5·5H2O. All the thirteen independent oxygen sites of the structure are involved in H-bonding, as donors or as acceptors. This confirms the pervasive nature and the important role played by the H-bonding network on the structural stability of inderite. The differences between the crystal structure of the two dimorphs inderite and kurnakovite are discussed.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)