Informace o publikaci
Fluorwavellit a variscit z Počepic u Sedlčan (Česká Republika)
| Autoři | |
|---|---|
| Rok publikování | 2016 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Bulletin Mineralogicko-Petrologickeho Oddeleni Narodniho Muzea v Praze |
| Fakulta / Pracoviště MU | |
| Citace | |
| Klíčová slova | Chemical composition, Czech Republic, Fluorwavellite, Mn-oxides, Phosphate occurence, Počepice, Sedlčany, Unit-cell parameters, Variscite |
| Přiložené soubory | |
| Popis | 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) A, V 1166.9(3) A3. Empirical formula of fluorwavellite is possible to express as (Al2.91Fe0.03)?2.94 (PO4)2.00(F0.84(OH)0.16)?1.00(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) A, V 1642.6(4) A3 (light pink sample); a 9.902(1), b 9.660(2), c 17.177(2) A, V 1643.1(5) A3 (light blue sample); a 9.901(2), b 9.659(2), c 17.179(3) A, V 1642.8(6) A3 (red sample) and a 9.903(2), b 9.657(3), c 17.181(4) A, V 1642.9(7) A3 (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). |