Beshtauite, (NH4)2(UO2)(SO4)2{middle dot}2H2O, a new mineral from Mount Beshtau, Northern Caucasus, Russia

Abstract

A new mineral beshtauite, (NH 4 ) 2 (UO 2 )(SO 4 ) 2 ·2H 2 O, was found in the oxidation zone of the Beshtau uranium deposit, Mount Beshtau, Stavropol region, Northern Caucasus, Russia, and named after the locality. It is associated with rozenite, gypsum, lermontovite, and older marcasite, pyrite, halloysite, and opal. Beshtauite occurs as well-shaped short-prismatic crystals up to 0.1 × 0.15 × 0.2 mm, their clusters and crusts up to 0.5 mm across growing on marcasite. Beshtauite is transparent, light green. The luster is vitreous. The mineral fluoresces strongly yellow-green under both short-and long-wave UV irradiation. It is brittle. The Mohs hardness is ca. 2. Cleavage was not observed. D calc is 3.046 g/cm 3 . Beshtauite is optically biaxial (+), α = 1.566 (3), β = 1.566(3), γ = 1.592(3), 2V meas < 10°. The chemical composition (wt%, electron microprobe data, H 2 O by difference) is: (NH 4 ) 2 O 10.33, UO 3 53.21, SO 3 29.40, H 2 O calc 7.06, total 100.00. Content of (NH 4 ) 2 O was calculated from measured nitrogen content: 5.56 wt% N. The empirical formula, calculated on the basis of 12 O apfu, is (NH 4 ) 2.12 U 0.99 S 1.96 O 9.91 (H 2 O) 2.09 . Beshtauite is monoclinic, P2 1 /c, a = 7.7360(8), b = 7.3712(5), c = 20.856(2) Å, β = 102.123(8)°, V = 1162.76(19) Å 3 , Z = 4 (from single-crystal X-ray diffraction data). The strongest reflections of the X-ray powder pattern [d (Å), I(hkl)] are: 6.86, 100(011, 102); 5.997, 19(012); 5.558, 15(102); 5.307, 36(111,110); 5.005, 35(013,112); 3. 410, 38(114,204,106); 3.081, 24(016); 2.881, 20(106,123). The crystal structure was solved by direct methods and refined on the basis of 2677 independent reflections with I > 4σ(I) to R 1 = 0.093. The structure is based upon [UO 2 (SO 4 ) 2 (H 2 O)] 2-layers consisting of corner-sharing UO 6 (H 2 O) pentagonal bipyramids and SO 4 tetrahedra. The layers are coplanar to (102) and are linked via hydrogen bonding that involve interlayer NH 4 + ions and H 2 O molecules. Beshtauite is important indicator mineral: its presence can be considered as an evidence of transportation of U 6+ in nature in forms of mobile complexes of uranyl cation with ammonia or polyamines.

Novograblenovite from Radlin, Upper Silesia, Poland and its relation to ‘redikortsevite’

“…The peak at 2825 cm –1 is a Fermi resonance doublet of overtone 2ν 4 with ν 1 normal mode (Larkin, 2011). The band at 3250 cm –1 (Majzlan et al , 2013; Pekov et al , 2014) corresponds to NH 4 + stretching vibrations. Frequencies below 303 cm –1 denote crystal lattice vibrations.…”

Oldsite, K2Fe2+[(UO2)(SO4)2]2(H2O)8, a new uranyl sulfate mineral from Utah, USA: its description and implications for the formation and occurrences of uranyl sulfate minerals

“…5.Ternary diagram showing the composition of the 42 well-characterised uranyl sulfate minerals. References: Burns, 2001; Burns et al ., 2003; Kampf et al ., 2014, 2015a, 2015b, 2015c, 2017a, 2017b, 2017c, 2017d, 2018a, 2018b, 2019a, 2019b, 2019c, 2020, 2021, 2022a, 2022b, 2022c; Kasatkin et al ., 2022, Mereiter, 1982; Pekov et al ., 2014; Plášil et al ., 2011, 2012a, 2012b, 2012c, 2013a, 2013b, 2014a, 2014c, 2015a, 2015b; Plášil and Škoda, 2015.

Fig. 6.The structural units of 42 well-characterised uranyl sulfate minerals characterised by the charge-deficiency per anion ( CDA ) value and its relationship with the molar proportion of the H 2 O and SO 4 in the structural units (s.u.).

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Redcanyonite, (NH4)2Mn[(UO2)4O4(SO4)2](H2O)4, a new zippeite-group mineral from the Blue Lizard mine, San Juan County, Utah, USA

“…A weak band found at 1615 cm –1 is assigned as the ν 2 (δ)-bending vibration of hydrogen-bonded crystalline water. A medium strong band at 1408 cm –1 is assigned to the N–H bending vibration of NH 4 + molecules (Pekov et al , 2014).

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