Horákite, ideally (Bi 7 O 7 OH)[(UO 2) 4 (PO 4) 2 (AsO 4) 2 (OH) 2 ]•3.5H 2 O, is a new uranyl mineral discovered on a specimen originating from Jáchymov, Czech Republic (most probably from the Geister vein, Rovnost mine). It occurs as a supergene alteration mineral in association with phosphuranylite (overgrowing older metatorbernite-metazeunerite) in a quartz gangue with abundant tennantite. Horákite forms greenish-yellow to pale yellow prismatic crystals clustering to acicular aggregates, up to 1 mm across. Crystals are transparent to translucent with a vitreous luster. The mineral has a light yellow streak. Estimated Mohs' hardness is ~2. The cleavage is perfect on {100}. The calculated density is 6.358 g/cm 3. Horákite is optically biaxial (+), α ≈ 1.81, β ≈ 1.84, γ ≈ 1.88 (measured in white light); 2V obs. is 78(1)°, 2V calc. is 83°; non-pleochroic. The optical orientation is X = b, Z ≈ c. Electron-microprobe analysis yielded the empirical formula (Bi 7.01 Pb 0.14)O 7 OH[(U 1.01 O 2) 4 (P 1.03 O 4) 2 (As 0.74 Si 0.23 O 4) 2 (OH) 2 ]•3.5H 2 O based on 37.5 O apfu. Horákite is monoclinic, C2/c, a = 21.374(2), b = 15.451(3), c = 12.168(2) Å, β = 122.26(1)° and V = 3398.1(10) Å 3 , Z = 4. The eight strongest X-ray powder-diffraction lines are [d obs Å(I)(hkl)]: 11.77(100)(110), 6.21(23)(-202), 5.55(23)(310,-112), 4.19(27)(-331), 3.54(61)(510,-423), 3.29(20)(331), 3.14(58)(241, 023) and 3.02(98)(150, 113,-533, mult.). The crystal structure refinement of horákite, refined to R = 5.95 % for 1774 unique observed reflections, revealed a novel sheet structure. It consists of topologically unique [(UO 2) 4 (PO 4) 2 (AsO 4) 2 (OH) 2 ] sheets (i.e., horákite topology), and an interstitial {(Bi 7 O 7 OH) (H 2 O) 3.5 } complex. Sheets result from the polymerization of UO 7 bipyramids by sharing edges to form tetrameric units; tetrahedrally coordinated sites are linked to the UO 7 both monodentately (T1 to U1) and bidentately (T2 to U2). The mineral is named after František Horák (1882-1919), the mining engineer in Jáchymov, and his grandson, Vladimír Horák (born 1964), an amateur mineralogist and expert on the mining history of the Jáchymov ore district.

The crystal structure of the organic mineral refikite has been determined. The mineral was found in joints in bark and wood from pine trees in the 'V Borkách' peat deposit near the town of Krásno, Slavkovský les Mountains, western Bohemia, Czech Republic. It forms white to light-yellow polycrystalline crusts or randomly intergrown, transparent, colourless, very thin, acicular crystals up to 0.2À0.5 mm long. Sometimes, colourless-to-white elongated prismatic crystals up to 1À1.5 mm in size were encountered. The mineral is soft (Mohs hardness~1) and very brittle, with an uneven fracture. No visible cleavage was discerned. Crystals have a greasy-to-glassy lustre; fine crystal aggregates have a pearly lustre. Refikite, empirical formula C 20 H 34 O 2 or C 19 H 33 COOH, is a derivative of abietic acid. It is orthorhombic, space group P2 1 2 1 2, with a = 22.6520(7), b = 10.3328(3), c = 7.6711(2) Å , V = 1795.49(9) Å 3 , Z = 4. Refikite comprises two closely related compounds based on perhydrophenanthrene. The major component has two axial methyl groups, one terminal carboxylic group and one terminal propan-2-yl (isopropyl) group joined to the three fused rings in the same fashion as in abietic acid. However, the fused ring system is fully reduced (contains single bonds only). In the minor component, the terminal propan-2-yl group is replaced by a propen-2-yl (methylvinyl) group. The crystal structure is stabilized by strong O_HÀO hydrogen bonds. High-resolution mass spectroscopy (HRMS) confirmed a molecular mass of 306 and the formula C 20 H 34 O 2 . Hydrogen-1 and carbon-13 nuclear magnetic resonance (NMR) spectroscopy showed the presence of four methyl groups in the major component; infrared (IR), Raman and NMR spectra are consistent with the structure. The HRMS, IR and Raman spectroscopy methods confirmed the presence of a minor component containing the propen-2-yl group replacing the propan-2-yl group. This is also reflected in a shortened C15ÀC17 single bond metric of 1.468(6) Å shown by single-crystal X-ray analysis. The trivial name of the major component of refikite is tetrahydroabietic acid or abietan-18-oic acid. This work represents the first proof of the existence of abietic acid derivatives as naturally occurring species.

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A rare uranium supergene minerals, phurcalite and uranophane-beta, were found in association with metaautunite at fissures of granitoid rocks in the active Wagner quarry in Ruprechtice near Liberec (northern Bohemia, Czech Republic). Phurcalite occurs there as bright to deep yellow coatings with an area up to 10 × 3 mm in size composed of acicular to columnar crystals up to 0.5 mm in length. It is orthorhombic, space group Pbca, the unit-cell parameters refined from X-ray powder diffraction data are: a 17.3973(18), b 16.0161(15), c 13.5693(19) Å, V 3780.9(5) Å3. Chemical analyses of phurcalite correspond to the empirical formula Ca2.20(UO2)3.06(PO4)1.96(AsO4)0.04O2.26·7H2O. Uranophane-beta forms a relatively abundant pale yellow coatings of up to 2 × 2 cm in size composed of translucent to transparent acicular crystals with a vitreous lustre and a length of up to 0.2 mm. It is monoclinic, space group P21/a, the unit-cell parameters refined from X-ray powder diffraction data are: a 13.959(2), b 15.5420(16), c 6.6227(9) Å, β 91.43(1)o and V 1436.3(2) Å3. Chemical analyses of uranophane-beta correspond to the empirical formula Ca1.09(UO2)1.99[(SiO3OH)1.68 (PO4)0.29(AsO4)0.03]Σ2.00·5H2O. Metaautunite occurs there as abundant light yellow aggregates with an area up to some cm2 in size composed of tiny (up to 0.5 mm) tabular crystals or rarely as well-developed individual tabular crystals up to several mm in size. It clearly differs from other minerals in the association by very strong yellow-green luminescence in both short- and long-wave UV radiation. It is tetragonal, space group P4/nmm, the unit-cell parameters refined from X-ray powder diffraction data are: a 7.006(2), c 16.899(4) Å and V 829.4(6) (5) Å3. Chemical analyses of metaautunite correspond to the empirical formula Ca1.03(UO2)2.09(PO4)1.96(AsO4)0.04·6H2O.