Krásnoite, the fluorophosphate analogue of perhamite, from the Huber open pit, Czech Republic and the Silver Coin mine, Nevada, USA
| Autor: | Jiří Sejkora, Neil A. Ball, Timothy J. Bastow, Ian E. Grey, P. M. Adams, Sj Mills, Mati Raudsepp, Mark A. Cooper, A. R. Kampf |
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| Rok vydání: | 2012 |
| Předmět: |
010504 meteorology & atmospheric sciences
biology Platy Infrared spectroscopy Crystal structure 010502 geochemistry & geophysics biology.organism_classification 01 natural sciences chemistry.chemical_compound Crystallography symbols.namesake chemistry Geochemistry and Petrology Ultraviolet light symbols Sodium polytungstate Mohs scale of mineral hardness Crystal twinning Raman spectroscopy 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 76:625-634 |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/minmag.2012.076.3.13 |
| Popis: | Krásnoite is a new mineral (IMA2011-040) from the Huber open pit, Krásno ore district, Czech Republic and the Silver Coin mine, Nevada, USA. Krásnoite is the fluorophosphate analogue of perhamite. Krásnoite occurs as compact to finely crystalline aggregates, balls and rosette-like clusters up to 1 mm across. Individual crystals are platy, show a hexagonal outline and can reach 0.1 mm on edge at Krásno and 0.4 mm at Silver Coin. At both localities, krásnoite occurs very late in phosphaterich paragenetic sequences. Krásnoite crystals are partly transparent with a typically pearly lustre, but can also appear greasy (Krásno) or dull (Silver Coin). The streak is white and the hardness is 5 on the Mohs scale. Crystals are brittle, have an irregular fracture, one imperfect cleavage on {001} and are not fluorescent under SW and LW ultraviolet light. Penetration twinning ⊥ {001} is common. The density for both Krásno and Silver Coin material is 2.48(4) g cm–3, measured by the sink–float method in an aqueous solution of sodium polytungstate. The calculated density is 2.476 g cm–3 (Krásno). Krásnoite crystals are uniaxial (+), with ω = 1.548(2) and ε = 1.549(2) (Krásno) and ω = 1.541(1) and ε = 1.543(1) (Silver Coin). The simplified formula of krásnoite is: Ca3Al7.7Si3P4O23.5(OH)12.1F2·8H2O. Krásnoite is trigonal, space group Pm1, with a = 6.9956(4), c = 20.200(2) Å, V = 856.09(9) Å3 and Z = 3. Raman and infrared spectroscopy, coupled with magic-angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, confirmed the presence of PO3F, PO4, SiO4, H2O and OH in the crystal structure of krásnoite. |
| Databáze: | OpenAIRE |
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