IMA 2004-022 e IMA 2004-038: šreinite e slavkovite

[Marco E. Ciriotti]

I nomi di queste due nuove specie figurano sul numero 2/2006 di Akademický bulletin "Atlas minerálů České a Slovenské republiky" in lingua ceca: http://abicko.avcr.cz/bulletin_txt_show ... &Poradi=18

Šreinite (IMA 2004-022) Pb2(UO2)11(BiO)8(PO4)5(OH)19·6H2O
Slavkovite (IMA 2004-038) Cu13(AsO4)6(AsO3OH)4·23H2O

Nulla più è dato a sapere.

[Marco E. Ciriotti]

Una breve descrizione (non quella tipo) della slavkovite (IMA 2004-038) è nel file accluso.

Referenza:
• Sejkora, J., Škoda, R., Ondruš, P. (2006): New naturally occurring mineral phases from Krásno-Horní Slavkov area, western Bohemia, Czech republic. Journal of the Czech Geological Society, 51(1-2), 159-187.

[Marco E. Ciriotti]

La pubblicazione della descrizione-tipo della šreinite è avvenuta.
Ecco, qui di seguito, referenza e abstract.

Referenza:
• Sejkora, J. & Čejka, J. (2007): 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. Neues Jahrbuch für Mineralogie, Abhandlungen, 184, 197-206.

Abstract:
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.

[Marco E. Ciriotti]

Pregasi notare che la formula, ora definitiva, Pb(UO2)4(BiO)3(PO4)2(OH)7·4H2O, è diversa da quella di IMA 2004-022 proposta per l'approvazione alla CNMNC dell'IMA.

Analogamente la formula della asselbornite va rivista come segue: Pb(UO2)4(BiO)3(AsO4)2(OH)7·4H2O.

[Marco E. Ciriotti]

Šreinite e asselbornite formano una serie continua.
Ba- e Ca-dominanti dell'asselbornite e della šreinite sono fasi possibilmente presenti in natura.

Chi fosse interessato al PDF della descrizione-tipo, non ha che da chiederlo.

[Marco E. Ciriotti]

La pubblicazione della descrizione-tipo della slavkovite non è ancora avvenuta.

[Marco E. Ciriotti]

La descrizione-tipo della sklavkovite è ora nella pipeline del Canadian Mineralogist.

Referenza:
• Sejkora, J., Plášil, J., Ondruš, P., Veselovský, F., Císarová, I., Hloušek, J. (2010): Slavkovite, Cu13(AsO4)(AsO3OH)4•23H2O – a new mineral from Horní Slavkov and Jáchymov, Czech Republic – description and crystal-structure determination. Canadian Mineralogist, 48, (in press).

[Marco E. Ciriotti]

Referenza:
• Sejkora, J., Plášil, J., Ondruš, P., Veselovský, F., Císarová, I., Hloušek, J. (2010): Slavkovite, Cu13(AsO4)(AsO3OH)4•23H2O – a new mineral from Horní Slavkov and Jáchymov, Czech Republic – description and crystal-structure determination. Canadian Mineralogist, 48, 1157-1170.

Abstract:
Slavkovite, Cu13(AsO4)6(AsO3OH)4·23H2O, is a newly discovered supergene mineral from the Geschieber vein, Svornost mine at the Jáchymov (St. Joachimsthal) ore district, Czech Republic, commonly associated with lavendulan, geminite, lindackerite and ondrušite. It forms coatings of pale green rosettes up to 1 mm across or individual spherical aggregates up to 5 mm across. Individual acicular to lath-like crystals are up to 1 mm long and 0.05 mm thick, and are colorless with a greenish tint. Slavkovite is pale green, translucent (aggregates) to colorless with a greenish tint, transparent (crystals). It has a white streak and a vitreous luster, and does not fluoresce under both short- and long-wave ultraviolet light. The cleavage on {011} is perfect, and on {010}, it is good. The Mohs hardness is ~3.5–4; slavkovite is very brittle, with an irregular fracture. Its measured density, 3.05(1) g/cm3, is identical to the calculated one. Slavkovite is biaxial positive; the indices of refraction are ' 1.591(2), ?' 1.620(2), ' 1.701(2), and the 2V (calc.) is approximately 64°. It is moderately pleochroic (X light gray to colorless, Y very light greenish gray, Z light green). Slavkovite is triclinic, space group P-1, a 6.408(3), b 14.491(5), c 16.505(8) Å, 102.87(3), ? 101.32(5), 97.13(3)°, V 1442(1) Å3, Z = 1, ac = 0.4422:1:1.1390. The strongest eight lines in the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are as follows: 15.70(3)(001), 11.98(100)(01), 6.992(3)(01, 020), 5.992(6)(02), 3.448(5) (040), 2.967(5)(05), 2.4069(4)(14), 2.4002(4)(115, 35, 06, 02). The chemical analyses made with an electron microprobe yielded FeO 0.12, CuO 39.93, Al2O3 0.13, As2O5 44.71, H2O 17.31, total 102.20 wt.%. The resulting empirical formula on the basis of 63(O, OH, H2O) anions is (Cu12.96Al0.07Fe0.04)13.07(AsO4)6.11 (AsO3OH)3.93·22.83H2O. The ideal end-member formula, Cu13(AsO4)6(AsO3OH)4·23 H2O, requires CuO 39.26, As2O5 43.36, H2O 17.10, total 100.00 wt. %. The crystal structure of slavkovite has been solved by direct method and refined to a final Robs of 4.37% on the basis of 6613 observed reflections collected on a single-crystal diffractometer with MoK X-radiation. The crystal structure is based upon sheets consisting of copper polyhedra linked by arsenate and hydrogen arsenate tetrahedra. The sheets are linked by bridging Cu6– polyhedra. In the asymmetric unit of the slavkovite unit-cell, seven symmetrically independent Cu2+ atoms, five As5+ atoms and 34 O atoms were found. Two of the oxygen atoms belong to OH– groups and fourteen to H2O molecules. Slavkovite possesses a unique crystal structure that has not been found in any mineral or synthetic compound before. It was named after its first occurrence in the Krásno Sn–W ore district, near Horní Slavkov, Czech Republic. Selected data for slavkovite from this locality are also given.

[giuseppe daniele]

Volevo chiedere se è giusto parlare di "gruppo dell'asselbornite", come è affermato in Mineralienatlas Lexikon sotto la classificazione di H. Strunz. Questo gruppo può comprendere asselbornite e šreinite, isostrutturali.

Giuseppe Daniele

[Marco E. Ciriotti]

Senz'altro sì. Anche se le due strutture non sono mai state risolte intuibilmente le due specie sono isostrutturali e pertanto formano un gruppo.
Poichè l'asselbornite è stata scoperta per prima essa ha priorità per la denominazione del gruppo.

Asselbornite Pb(UO2)4(BiO)3(AsO4)2(OH)7·4H2O cub Im3m, I432, Im3, I23 15.6568 15.6568 15.6568 90.00 90.00 90.00 5 3840.39
Šreinite Pb(UO2)4(BiO)3(PO4)2(OH)7·4H2O cub Im3m, I432, Im3, I23 15.5728 15.5728 15.5728 90.00 90.00 90.00 5 3776.59