Инд. авторы:	Seryotkin Y.V., Sokol E.V., Kokh S.N., Murashko M.N.
Заглавие:	Natural Cr3+-rich ettringite: occurrence, properties, and crystal structure
Библ. ссылка:	Seryotkin Y.V., Sokol E.V., Kokh S.N., Murashko M.N. Natural Cr3+-rich ettringite: occurrence, properties, and crystal structure // Physics and Chemistry of Minerals. - 2018. - Vol.45. - Iss. 3. - P.279-292. - ISSN 0342-1791. - EISSN 1432-2021.
Внешние системы:	DOI: 10.1007/s00269-017-0917-y; SCOPUS: 2-s2.0-85028016773; WoS: 000429105200006;
Реферат:	eng: Cr3+-rich ettringite with Cr3+-> Al substitution and Cr/(Cr + Al) ratios up to 0.40-0.50 was found in mineral assemblages of the Ma'aleh Adumim area of Mottled Zone (Judean Desert). The Cr3+-rich compositions were the latest in the thaumasite -> ettringite-thaumasite solid solution -> ettringite -> ettringite-bentorite solid solution series. The mineral-forming solution was enriched in Cr3+ and had a pH buffered by afwillite at similar to 11-12. Chromium was inherited from larnite rocks produced by high-temperature combustion metamorphic alteration of bioproductive calcareous sediments. The Cr/(Cr + Al) ratios are within 0.10-0.15 in most of the analysed crystals. This degree of substitution imparts pink colouration to the crystals, but does not affect their habit (a combination of monohedra and a prism). The habit changes to pyramid faces in coarse and later Cr3+-bearing crystals as Cr/(Cr + Al) ratios increase abruptly to 0.40-0.50. Single-crystal XRD analysis of one Cr-free and two Cr3+-rich samples and their structure determination and refinement indicate that the Cr-rich crystals (with Cr/(Cr + Al) to 0.3) preserve the symmetry and metrics of ettringite. The Ca-O bonding network undergoes differentiation with increase of Cr3+ concentration at octahedral M sites. The compression of Ca2 and expansion of Ca1 polyhedra sub-networks correlates with the degree of Cr3+-> Al substitution.
Ключевые слова:	THAUMASITE; FE-ETTRINGITE; GROUP MINERALS; TETRACALCIUM ALUMINOFERRITE; CENTRAL JORDAN; CENTER-DOT 12H(2)O; ISRAEL; SOLID-SOLUTION SERIES; Morphology; Crystal structure; Chromium; Bentorite; Cr3+-ettringite; MOTTLED ZONE COMPLEX; SOLUBILITY;
Издано:	2018
Физ. характеристика:	с.279-292