Šreinite from Horní Halže, the Krušné hory Mountains, Czech Republic, a new mineral species, its comparison with asselbornite from Schneeberg, and new data for asselbornite
Sejkora, Jiří Čejka
published: Oct 31, 2007
ArtNo. ESP154018402007, Price: 29.00 €
Šreinite, ideally Pb(UO2)4(BiO)3(PO4)2(OH)7. 4H2O, is the (PO4)-dominant analogue of asselbornite. It occurs in fissures of quartz gangue at an agrarian dumping near Horní Halže, 2 km WSW from Měděnec, Krušné hory Mountains, Czech Republic. It forms irregular coatings up to 0.2 mm thick with a rugged glossy surface (area up to 2 × 3 mm), no crystals were observed. It is brittle with uneven fracture, cleavage none observed; the Mohs hardness is 2-4. It has a yellow color with an orange tint, pale yellow streak and vitreous to (sub)adamantine luster. No fluorescence was observed in ultraviolet light. It is opaque, translucent only in thin fragments, isotropic with high refractive index (>1.74). The calculated density (for the empirical formula) is 5.20 g/cm3. Šreinite originated by supergene weathering and was associated with uranosphaerite, goethite, Pb-bearing phosphuranylite, metatorbernite, bismutoferrite, kasolite and uranophane. The name šreinite is in honor of Vladimír Šrein (*1953), a Czech mineralogist, who found the first specimens of this mineral. Šreinite is cubic, possible space groups Im3m, I432, Im3 or I23. The unit-cell parameter, refined from powder data, is a = 15.5728(7) Å, V = 3776.6(5) Å3 and Z = 5. The eight strongest reflection of the X-ray powder-diffraction pattern [d in Å (Irel)(hkl)] are: 5.513 (53)(220), 4.499 (48)(222), 4.163 (100)(321), 3.671 (77)(411,330), 3.484 (31)(420), 3.179 (99)(422), 2.596 (54)(442,600), 1.9776 (30)(732,651). Chemical analyses yielded the average composition BaO 0.08, CaO 0.18, MgO 0.01, PbO 7.78, Bi2O3 29.73, SiO2 0.18, P2O5 3.41, As2O5 3.79, UO3 49.23, H2O (5.68), total (100.07) wt. %, corresponding to (Pb0.83Ca0.08Ba0.01Mg0.01)Σ0.93(UO2)4.10(BiO)3.04[(PO4)1.15(AsO4)0.78(SiO4)0.07]Σ2.00(OH)7.02.4H2O on the basis of 2 atoms in the tetrahedral site (P+As+Si). The ideal formula Pb(UO2)4(BiO)3(PO4)2(OH)7.4H2O requires PbO 9.52, Bi2O3 29.83, P2O5 6.06, UO3 48.82, H2O 5.77, total 100.00 wt. %. The new mineral šreinite was compared (inclusive infrared and Raman spectra) with asselbornite from Schneeberg, Germany and new data for asselbornite are therefore also given.