Acta Musei Moraviae

Deliensite and Fe sulfates from the fluorite deposit Běstvina (Czech Republic)

A rare mineral deliensite, Fe[(UO₂)₂(SO₄)₂(OH)₂](H₂O)₇, was found in material from the abandoned Běstvina fluorite-baryte deposit, Železné hory Mountains, eastern Bohemia. This is the first occurrence of this mineral in the Czech Republic outside the Jáchymov ore area. Deliensite occurs as greenish yellow to yellow, darker olive green or brownish green crystalline coatings covering the area up to 1 × 0,5 cm, formed by elongated tabular crystals 50 μm in length. Deliensite is orthorhombic, space group Pnn2, with the unit-cell parameters refined from X-ray powder diffraction data: a 15.917(4), b 16.301(4), c 6.9104(13) Å, and V 1793.0(6) ų. Chemical analyses of deliensite correspond to the empirical formula (Fe_0.73Mn_0.11Zn_0.03Ca_0.01Mg_0.01)_Σ0.89(UO₂)_2.08(SO₄)_1.96(VO₄)_0.04(OH)_1.89·7H₂O, calculated based on the sum of S+V = 2 apfu. The iron sulfates, rozenite and szomolnokite, were found as white aggregates and coatings up to 2 × 2 cm in size. Both sulfates are monoclinic with the following unit-cell parameters refined from X-ray powder diffraction data: rozenite (space group P2₁/n), a 5.9723(10), b 13.6260(18), c 7.9748(18) Å, β 90.486(14)° and V 648.96(14) ų; szomolnokite (space group C2/c), a 7.093(2), b 7.5484(18), c 7.784(3) Å, β 118.65(2)° and V 365.7(3) ų. The origin of studied minerals is connected with simultaneous (sub)recent weathering of primary uraninite/coffinite and pyrite in the conditions of the abandoned mining tunnels.