Original paper

Jáchymovite, (UO2) 8 (SO4) (OH)14 · 13 H2O, a new uranyl mineral from Jáchymov, the Krušné hory Mts., Czech Republic, and its comparison with uranopilite

Čejka, J.; Sejkora, J.; Mrázek, Z.; Urbanec, Z.; Jarchovský, T.

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Neues Jahrbuch für Mineralogie - Abhandlungen Band 170 Heft 2 (1996), p. 155 - 170

32 references

published: Jul 17, 1996

DOI: 10.1127/njma/170/1996/155

BibTeX file

ArtNo. ESP154017002003, Price: 29.00 €

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Abstract

Jáchymovite, (UO2)8(SO4)(OH)14 · 13H2O, is monoclinic, with space group P12, 1 or P121/m1 inferred from powder diffraction data, and with a = 18.553 (8)Å, b = 9.276 (2)Å, c = 13.532 (7)Å, ß = 125.56 (2)°, V = 1894 (2)Å3, Z = 2 and Dcalc = 4.79 g · cm-3. The strongest lines in XRD pattern are (d in Å, I, hkl): 7.56 (100, 200), 7.13 (48, 101), 3.771 (34, 400), 3.554 (20, 50-3), 3.206 (13, 32-3), 3.234 (10, 22-3), 2.052 (8, 142). Jáchymovite forms minute acicular crystals up to 0.1 mm long that make up crystalline coatings up to some cm2 on gangue. It has yellow colour, pale yellow streak, vitreous lustre, yellow fluorescence under UV light (254 and 366 nm) and its translucent. It also has very good cleavage parallel to [010], conchoidal fracture, brittle tenacity. The mineral is biaxial negative with refraction indices ɑ = 1.715 (2), ß = 1.718 (2) and 𝛾= 1.720 (2) (589 nm), 2Vcalc = 78°, pleochroism Y = pale yellow, Z = yellow. Chemical analysis yields an average composition of UO384.20, SO32.79, H2O 13.32, total 100.31 wt. %, leading to a formula (UO2)8(SO4)(OH)14 ⬝ 13 H2O. The mineral formed as an alteration product of strongly weathered uraninite, it occurs in the dolomite -uraninite veins at Jáchymov, Krušné hory Mts., Western Bohemia, Czech Republic, in association with gypsum, uranopilite and uraninite. The name is for the locality Jáchymov. Jáchymovite is compared with uranopilite and X-ray powder diffraction data, thermal analysis and infrared spectra for both minerals are given.

Keywords

Jáchymovite • new mineral • hydrated uranyl hydroxosulphate • X-ray powder diffraction • thermal analysis • infrared spectroscopy • uranopilite • Jáchymov • Czech Republic