Magnesioleydetite and straβmannite, two new uranyl sulfate minerals with sheet structures from Red Canyon, Utah

Abstract

Magnesioleydetite (IMA2017-063), Mg(UO2)(SO4)2·11H2O, and straβmannite (IMA2017-086), Al(UO2)(SO4)2F·16H2O, are two new minerals from mines in Red Canyon, San Juan County, Utah, USA. Magnesioleydetite occurs in the Markey mine and straβmannite occurs in both the Markey and Green Lizard mines. Both minerals are secondary phases found in efflorescent crusts on the surfaces of mine walls. Magnesioleydetite occurs in irregular aggregates (to ~0.5 mm) of blades (to ~0.2 mm) exhibiting the following properties: transparent to translucent; pale green–yellow colour; vitreous lustre; white streak; non-fluorescent; brittle; Mohs hardness ≈ 2; irregular fracture; one perfect cleavage on {001}; and calculated density = 2.463 g/cm3. Straβmannite occurs in irregular aggregates (to ~0.5 mm) of equant crystals (to ~0.2 mm) exhibiting the following properties: transparent; light yellow–green colour; vitreous to greasy lustre; nearly white streak; bright greenish-blue fluorescence; somewhat brittle, Mohs hardness ≈ 1½; irregular fracture; one good cleavage on {001}; measured and calculated densities of 2.20(2) and 2.173 g/cm3, respectively; optically biaxial (–); α = 1.477(2), β = 1.485(2) and γ = 1.489(2) (white light); 2Vmeas. = 72(2)°; dispersion r > v (slight); orientation Y = b, X ∧ c = 20° (in obtuse β); pleochroism with X = nearly colourless, Y = pale green–yellow and Z = light green–yellow (X < Y < Z). The empirical formulas for magnesioleydetite and straβmannite are (Mg0.56Fe0.26Zn0.11Mn0.01)Σ0.94(U0.99O2)(S1.015O4)2·11H2O and Al1.00Na0.16(U0.99O2)(S1.00O4)2[F0.58(OH)0.42]·16H2O, respectively. Magnesioleydetite is monoclinic, C2/c, a = 11.3513(3), b = 7.7310(2), c = 21.7957(15) Å, β = 102.387(7)°, V = 1868.19(16) Å3 and Z = 4. Straβmannite is monoclinic, C2/c, a = 11.0187(5), b = 8.3284(3), c = 26.6727(19) Å, β = 97.426(7)°, V = 2427.2(2) and Z = 4. The structures of magnesioleydetite (R1 = 0.016 for 2040 I > 2σI reflections) and straβmannite (R1 = 0.0343 for 2220 I > 2σI reflections) each contain uranyl-sulfate sheets based on the protasite-anion topology.

Chemically Induced Polytypic Phase Transitions in the Mg[(UO2)(TO4)2(H2O)](H2O)4 (T = S, Se) System

“…For instance, during our studies of the mixed uranyl sulfateselenate system with K + , 20 the absence of a continuous solid solution was observed, along with the absence of isotypic pure sulfates and selenates. In contrast, in the mixed uranyl sulfateselenate system investigation with Cs + , 21 ), 23 and magnesioleydetite (Mg(UO 2 )(SO 4 ) 2 (H 2 O) 11 ) 13 have been found as secondary U 6+ minerals forming in the oxidation zones of uranium mineral deposits.…”

“…The importance of the study of uranyl sulfates and selenates is in their relevance to the mineralogy and geochemistry of uranium in mine tailings and geological sites for the disposal of the radioactive wastes. Recent studies revealed a large number of different uranyl sulfate phases that form in the abandoned uranium mines, − which points out the high complexity of secondary processes responsible for the transport of uranium in the environment.…”

Structural complexity of natural uranyl sulfates

“…9. Among the studied uranyl sulfates it is mostly related to alwilkinsite-(Y), Y[(UO 2 ) 3 (SO 4 ) 2 O(OH) 3 ](H 2 O) 14 (Kampf et al, 2017c), bobcookite, NaAl(UO 2 ) 2 (SO 4 ) 4 (H 2 O) 18 (Kampf et al, 2015a), leydetite, Fe(UO 2 )(SO 4 ) 2 (H 2 O) 11 (Plá šil et al, 2013a), magnesioleydetite, Mg(UO 2 )(SO 4 ) 2 (H 2 O) 11 (Kampf et al, 2018d) and strassmannite, Al(UO 2 )(SO 4 ) 2 F(H 2 O) 16 (Kampf et al, 2018d).…”

Paramarkeyite, a new calcium–uranyl–carbonate mineral from the Markey mine, San Juan County, Utah, USA

“…It occurs on gypsum-coated asphaltum in association with andersonite, calcite, gypsum and natromarkeyite (Kampf et al , 2020a). Other new minerals recently described from the Markey mine are feynmanite (Kampf et al , 2019a), leószilárdite (Olds et al , 2017), magnesioleydetite (Kampf et al , 2019b), markeyite (Kampf et al , 2018), meyrowitzite (Kampf et al , 2019c), pseudomarkeyite (Kampf et al , 2020a), straβmannite (Kampf et al , 2019b) and uroxite (Kampf et al , 2020b).…”