Gurzhiite, Al(UO2)(SO4)(2)F center dot 10H(2)O, a new uranyl sulfate mineral with a chain structure from the Bykogorskoe deposit, Northern Caucasus, Russia
| Authors | |
|---|---|
| Year of publication | 2022 |
| Type | Article in Periodical |
| Magazine / Source | Mineralogical Magazine |
| MU Faculty or unit | |
| Citation | |
| Web | https://doi.org/10.1180/mgm.2022.34 |
| Doi | http://dx.doi.org/10.1180/mgm.2022.34 |
| Keywords | gurzhiite; new mineral; uranyl sulfate; chain crystal structure; Bykogorskoe deposit; Northern Caucasus |
| Description | Gurzhiite, ideally Al(UO2)(SO4)(2)F center dot 10H(2)O, is a new uranyl sulfate mineral from the Bykogorskoe U deposit, Northern Caucasus, Russia. It occurs as fine-grained aggregates forming veinlets up to 50 cm long in cracks of the brecciated rock. Gurzhiite aggregates are composed of small bladed crystals up to 0.1 mm across. Associated minerals include khademite and quartz. Gurzhiite is pale yellow in crystals, lemon yellow in aggregates, transparent with a vitreous lustre and a white streak. It is brittle and has an irregular fracture. Cleavage is good on {001}. The new mineral exhibits a bright yellow-green fluorescence under both longwave and shortwave UV radiation. Mohs hardness is similar to 2. D-meas = 2.52(3) g/cm(3) and D-calc = 2.605 g/cm(3). The mineral is biaxial (-) with alpha = 1.528(3), beta = 1.538(2), gamma = 1.544(3) (589 nm); 2V(meas) = 80(10)degrees and 2V(calc) = 75.1 degrees. The empirical formula calculated on the basis of 21(O + F) atoms per formula unit (apfu) is Al0.92Zn0.05Fe0.033+Na0.03U0.95S2.00O9.85F0.99 center dot 10.16H(2)O. Gurzhiite is triclinic, with space group P (1) over bar, a = 7.193(2), b = 11.760(2), c = 11.792(2) angstrom, alpha = 67.20(3), beta = 107.76(3), gamma = 89.99(3)degrees, V = 867.7(4) angstrom(3) and Z = 2. The five strongest lines of the powder X-ray diffraction pattern [d, angstrom (I, %)(hkl)] are: 10.24(100)(001); 5.40(14)((1) over bar(1) over bar1); 5.11(54)(002); 3.405(11)((2) over bar 11); and 3.065(11)((1) over bar(1) over bar3). The crystal structure of gurzhiite is based upon uranyl sulfate chains of the same type as in bobcookite and svornostite. Between the chains are two types of Al-octahedra - Al1(H2O)(6) and Al2F(2)(H2O)(4). The entire structure stability is maintained by a complex network of H bonds. The new mineral honours Russian mineralogist and crystallographer Dr. Vladislav V. Gurzhiy in recognition for his contributions to uranium mineralogy and crystallography. |
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