Hasanovite KNa(MoO<sub>2</sub>)(SO<sub>4</sub>)<sub>2</sub>, a New Mineral from Natural Underground Coal Fires at the Fan-Yagnob Coal Deposit, Tajikistan

The new mineral hasanovite KNa(MoO2)(SO4)2 was discovered in sublimates of a natural underground coal fire at the Fan-Yagnob coal deposit in the upper reaches of the Kuhi-Malik ravine in the Aini district, Central Tajikistan. The mineral is named in honor of the petrographer Abdurahim Hasanovich Hasanov (born 1933). Hasanovite occurs as small (50–200 µm) grains on a burnt siltstone in association with anhydrite, baryte, anglesite, molybdite, native tellurium, and understudied Sb-K, K-Mg, Tl-V, and Sn sulfates. The mineral is transparent, colourless with a vitreous luster and white streak. It is brittle, with no cleavage. VHN 103 (range from 84 to 113). The Mohs’ hardness is 3. Dmeas = 2.93(2) and Dcalc = 2.94 g/cm3. Hasanovite is colourless in transmitted light, pleochroism is not observed; it is optically biaxial (+), 2V = 50(3)°, α = 1.584(2), β(calc.) = 1.590(3), γ = 1.620(2) (590 nm). Strong lines in the Raman spectrum are as follows: 1034, 958, 916, 648, 469, 390, 273 and 232 cm–1. Hasanovite is insoluble in water and ethanol but soluble in HCl. The chemical composition studied by electron microprobe (wt %) is: Na2O 4.54, K2O 13.81, Tl2O 1.80, MoO3 38.75, SO3 40.10, total 99.00. The empirical formula, calculated on the basis of O = 10 atoms per formula unit, is K1.16Na0.58Tl0.03Mo1.06S1.98O10. The strongest lines in the powder X-ray diffraction pattern are [d, Å(I, %)(hkl)]: 7.30(36)(110); 6.57(48)(011); 4.34(75)(\(\overline 1 \)21); 3.64(100)(211); 3.44(58)(031); 3.34(74)(\(\overline 2 \)02, 022); 3.20(63)(\(\overline 2 \)12); 2.879(73)(\(\overline 2 \)31); 2.729(50)(140); 2.436(44)(\(\overline 1 \)23). Hasanovite is monoclinic, space group is P21/c, a =9.6225(2), b = 11.4049(3), c = 8.1421(2) Å, β = 99.1790(10)°, V = 882.10(4) Å3, Z = 4. The crystal structure (R1 = 2.7%) is close to the structure of synthetic K2(MoO2)(SO4)2. The holotype specimen of hasanovite is deposited in the collection of the Fersman Mineralogical Museum of RAS (Moscow), registration number 5568/1.