Magnesioleydetite and stra beta mannite, two new uranyl sulfate minerals with sheet structures from Red Canyon, Utah

摘要

Magnesioleydetite (IMA2017-063), Mg(UO2)(SO4)(2)center dot 11H(2)O, and stra beta mannite (IMA2017-086), Al(UO2)(SO4)(2)F center dot 16H(2)O, are two new minerals from mines in Red Canyon, San Juan County, Utah, USA. Magnesioleydetite occurs in the Markey mine and stra beta mannite 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 similar to 0.5 mm) of blades (to similar to 0.2 mm) exhibiting the following properties: transparent to translucent; pale green-yellow colour; vitreous lustre; white streak; non-fluorescent; brittle; Mohs hardness approximate to 2; irregular fracture; one perfect cleavage on {001}; and calculated density = 2.463 g/cm(3). stra beta mannite occurs in irregular aggregates (to similar to 0.5 mm) of equant crystals (to similar 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 approximate to 1 1/2; irregular fracture; one good cleavage on {001}; measured and calculated densities of 2.20(2) and 2.173 g/cm(3), respectively; optically biaxial (-); alpha = 1.477(2), beta = 1.485(2) and gamma = 1.489(2) (white light); 2V(meas.)= 72(2)degrees; dispersion r > v (slight); orientation Y= b, X boolean AND c= 20 degrees (in obtuse beta); pleochroism with X= nearly colourless, Y= pate green-yellow and Z= tight green-yellow (X < Y < Z). The empirical formulas for magnesioleydetite and stra beta mannite are (Mg0.56Fe0.26Zn0.11Mn0.01)(Sigma 0.94)(U0.99O2)(S1.015O4)(2)center dot 11H(2)O and Al1.00Na0.16(U0.99O2)(S1.00O4)(2)[F-0.58(OH)(0.42)]center dot 16H(2)O, respectively. Magnesioleydetite is monoclinic, C2/c, a= 11.3513(3), b = 7.7310(2), c= 21.7957(15) angstrom, beta=102.387(7)degrees, V= 1868.19(16) angstrom(3) and Z= 4. stra beta mannite is monoclinic, C2/c, a = 11.0187(5), b = 8.3284(3), c= 26.6727(19) angstrom, beta= 97.426(7)degrees, V = 2427.2(2) and Z= 4. The structures of magnesioleydetite (R-1 = 0.016 for 2040 I > 2 sigma I reflections) and stra beta mannite (R-1 = 0.0343 for 2220 I > 2 sigma I reflections) each contain uranyl-sulfate sheets based on the protasite-anion topology.