Fluorwavellite and variscite from Počepice near Sedlčany (Czech Republic)
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Abstract
An interesting mineral occurence of phosphates was found close to the Počepice village near Sedlčany (central Bohemia, Czech Republic). Recently defined fluorwavellite forms white spherical aggregates up to 14 mm across in fissures and cavities of contact metamorphic rocks (quartzite, chert, metagreywacke). It is orthorhombic, space group Pcnm with following unit-cell parameters refined from the X-ray powder diffraction data: a 9.614(1), b 17.360(2), c 6.9916(9) Å, V 1166.9(3) Å3. Empirical formula of fluorwavellite is possible to express as (Al2.91Fe0.03)Σ2.94(PO4)2.00(F0.84(OH)0.16)Σ1.00(OH)1.83·5H2O. Variscite occurs as light blue to light pink, red, white and colorless transparent crusts, spherical aggregates and columnar and dipyramidal crystals. All studied types belong to variscite of Messbach type with following orthorhombic unit-cell parameters: a 9.901(1), b 9.6584(9), c 17.178(2) Å, V 1642.6(4) Å3 (light pink sample); a 9.902(1), b 9.660(2), c 17.177(2) Å, V 1643.1(5) Å3 (light blue sample); a 9.901(2), b 9.659(2), c 17.179(3) Å, V 1642.8(6) Å3 (red sample) and a 9.903(2), b 9.657(3), c 17.181(4) Å, V 1642.9(7) Å3 (white to colorless sample). Their empirical formulae are: Al0.98(PO4)1.00F0.05·2H2O (light pink and red sample); Al0.97(PO4)1.00F0.04·2H2O (light blue sample); Al1.00(PO4)1.00F0.05·2H2O (white to colorless). Phosphates was found in association with Mn-oxides (hollandite, cryptomelane, asbolane, lithiophorite and undescribed Co-Mn-Mn dominant member of coronadite group).
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References
Anthony J. W., Bideaux R. A., Bladh K. W., Nichols M. C. (1997) Handbook of Mineralogy. Volume III Halides, hydroxides, oxides. 1-628, Mineral Data Publishing, Tucson, Arizona.
Biagoni C., Capalbo C., Pasero M. (2013) Nomenclature tunings in the hollandite supergroup. Eur. J. Mineral 25, 85-90.
Burlet C., Vanbrabant Y. (2015) Study of the spectro-chemical signatures of cobalt–manganese layered oxides (asbolane–lithiophorite and their intermediates) by Raman spectroscopy. J. Raman Spectrosc. 46, 941-952.
Kampf A. R., Adams P. M., Barwood H., Nash B. P. (2015) Fluorwavellite, IMA 2015-077. CNMNC Newsletter 28, 1862; Mineral. Mag. 79, 1859–1864.
Kniep R., Mootz D. (1973) Metavariscite - a redetermination of its crystal structure. Acta Cryst. B29, 2292-2294.
Kniep R., Mootz D., Vegas A. (1977) Variscite. Acta Crys. B33, 263-265.
Kodym O. Straka J. Štěpánek P. (2000) Geologická mapa 22-22 Sedlčany. Soubor geol. a ekol. účel. map přír. zdrojů. 1 s., Český geologický ústav, Praha.
Laugier J., Bochu B. (2011) LMGP-Suite of Programs for the interpretation of X-ray experiments. http://www.ccp14.ac.uk/tutorial/lmgp. přístup duben 2011.
Ostwald J. (1988) Mineralogy of the Groote Eylandt manganese oxides: A review. Ore Geology Reviews 4, 3-45.
Post J. E., Appleman D. E. (1994) Crystal structure refinement of lithiophorite. Am. Mineral. 79, 370-374.
Pouchou J. L., Pichoir F. (1985) “PAP” (φρZ) procedure for improved quantitative microanalysis. In: Microbeam Analysis (J. T. Armstrong, ed.). 104-106, San Francisco Press, San Francisco.
Roqué-Rosell J., Mosselmans J. F. W., Proenza J. A., Labrador M., Galí S., Atkinson K. D., Quinn P. D. (2010) Sorption of Ni by “lithiophorite–asbolane” intermediates in Moa Bay lateritic deposits, eastern Cuba. Chem. Geol. 275, 9-18.
Salvador P. S., Fayos J. (1972) Some aspects of the structural relationship between "Messbach-type" and "Lucin-type" variscites. Am. Mineral. 57, 36-44.
Sejkora J., Cícha J., Jebavá I. (2011) Minerální asociace fosfátů z Čížové u Písku (Česká republika). Bull. mineral.-petrolog. Odd. Nár. Muz.(Praha) 19, 1, 1-26.
Slačík J., Blüml A. (1977) Wavellit z Počepic na Sedlčansku. Čas. Mineral. Geol. 22, 4, 428.
Vanbrabant Y., Burlet C., Louis P. (2013) Mineralogical Characterization of Cobaltic Oxides from the Democratic Republic of Congo. In: Battle T., Moats M., Cocalia V., Oosterhof H., Alam S., Allanore A., Jones R., Stubina N., Anderson C., Wang S. (editors) Ni-Co 2013, 241-254. The Minerals, Metals & Materials Society.
Vrtiška L., Malíková R., Sejkora J., (2016) Zajímavý výskyt fosfátů v okolí Líštěnce u Votic (Česká republika). Bull. mineral.-petrolog. Odd. Nár. Muz. (Praha) 23, 1, 114-131.
Vrtiška L., Sejkora J., Nováková H., Vašinová Galiová M. (2013) Metatorbernit a lithioforit z uranového ložiska Předbořice (Česká republika). Bull. mineral.-petrolog. Odd. Nár. Muz. (Praha) 21, 2, 240-248.
www.geology.cz – mapový server České geologické služby; přístup říjen 2016.