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Zinconigerite-2N1S ZnSn2Al12O22(OH)2 and zinconigerite-6N6S Zn3Sn2Al16O30(OH)2 are two new minerals with different numbers and ratios of nolanite (N) and spinel (S) modules. Both phases have been discovered in the Xianghualing skarn, Hunan Province, China. Zinconigerite-2N1S (zn-2N1S) and zinconigerite-6N6S (zn-6N6S) are named for their chemical composition, number, and ratios of N-S modules, according to the nomenclature of the nolanite-spinel polysomatic series of Armbruster (2002). Both phases occur as aggregates, sub-to-euhedral crystals, with maximal dimensions up to 100 μm, within fluorite aggregates, and they are closely associated with phlogopite, chrysoberyl, magnetite, cassiterite, margarite, and nigerite-taaffeite group minerals. They do not show fluorescence in long- or short-wave ultraviolet light. The calculated densities are 4.456 g/cm3 for zn-2N1S and 4.438 g/cm3 for zn-6N6S. Optically, zn-2N1S is uniaxial (+) with ω = 1.83(1), ε = 1.84(2); zn-6N6S is uniaxial (+) with ω = 1.85(1), ε = 1.87(2) (λ = 589 nm). Their chemical compositions by electron-microprobe analyses give the empirical formulas (Zn0.734Mn0.204Na0.122Ca0.063Mg0.044)Σ1.166(Sn1.941Zn0.053Ti0.007)Σ2 A l 11.018 F e 0.690 3 + Z n 0.200 S i 0.092 12 O 22 (O H) 2 for zn-2N1S and Z n 1.689 M n 0.576 M g 0.328 F e 0.407 3 + Σ 3 S n 1.882 Z n 0.047 T i 0.071 Σ 22 A l 14.675 F e 1.088 3 + N a 0.13 C a 0.086 S i 0.017 Σ 15.996 O 30 (O H) 2 for zn-6N6S. Both phases have trigonal symmetry; the unit-cell parameters of zn-2N1S (P3m1) and zn-6N6S (R3m), refined from single-crystal X‑ray diffraction data, are, a = 5.7191(2) and 5.7241(2) Å, c = 13.8380(6) and 55.5393(16) Å, V = 391.98(3) and 1575.96(12) Å3, and Z = 1 and 3, respectively. The structure of zn-2N1S is characterized by the alternating O-T1-O-T2-O-T1 layers stacked along the c-axis, showing the connectivity of N-S-N. The polyhedral stacking sequence of zn-6N6S is 3 × (O-T1-O-T2-O-T2-O-T1), reflecting a N-S-S-N-N-S-S-N-N-S-S-N connectivity of the polysomatic structure. By contrast, the structure of zn-2N1S shows the elemental replacements of Al → Sn and Al → Zn, suggesting the substitution mechanism of 2Al → Zn + Sn. The complex substitution of Zn by multiple elements (Al, Fe3+, Mn, Mg) in the structure of zn-6N6S, is coupled with the low occupancy of Al5-octahedra. Fe3+ → Al substitution occurs in Al1-tetrahedra of both zn-2N1S and zn-6N6S. The new polysomes, zn-2N1S and zn-6N6S, likely crystallized under F-rich conditions during the late stages of the Xianghualing skarn formation. The discovery of zn-2N1S and zn-6N6S provides new insights into the crystal chemistry of the N-S polysomatic series and its origin. [ABSTRACT FROM AUTHOR]

Chukochenite, (Li0.5Al0.5)Al2O4, is a new mineral species from the Xianghualing skarn, Hunan Province, southern China. It occurs as subhedral to euhedral crystals up to 200 μm across in the green rock of Xianghualing skarn, closely associated with fluorite, phlogopite, chrysoberyl, margarite, chlorite, ferronigerite-2N1S, and zinconigerite-2N1S. The crystals are colorless and transparent with a vitreous luster. Chukochenite is brittle with irregular fracture, has a Mohs hardness of 8, and shows light red fluorescence under 253.7 nm UV radiation and light green fluorescence under 365 nm UV radiation. The calculated density is 3.771 g/cm3. Chukochenite is optically biaxial (–) with α = 1.79(2), β = 1.82(2), and γ = 1.83(2) (589 nm). The calculated 2V is 60°, with the optical orientations X, Y, and Z parallel to the crystallographic a, b, and c, respectively. Electron microprobe analysis (Li by LA-ICP-MS) yielded in wt% Al2O3 80.70, Fe2O3 8.16, Li2O 3.68, ZnO 3.25, MnO 2.49, MgO 1.70, Na2O 0.11, CaO 0.08, TiO2 0.02, K2O 0.01, and Cr2O3 0.01 (total 100.24 wt%), giving an empirical formula [(Li0.355Al0.138Na0.005Ca0.002)Σ0.5(Al0.145Fe+0.1473 Mg0.061Zn0.058Mn0.051Si0.001)Σ0.463]Al2O4 on a basis of 4 O atoms per formula unit. Chukochenite is orthorhombic, Imma, a = 5.659 (1), b = 16.898 (1), c = 7.994 (1) Å, V = 764.46 (8) Å3, and Z = 12. The nine strongest lines of powder XRD [d in Å (I) (hkl)] are: 2.405 (53) (231); 1.996 (29) (260); 1.535 (77) (303); 1.413 (100) (264); 1.260 (52) (2 12 0); 1.068 (36) (1 13 4); 1.039 (61) (503); 0.999 (59) (008); and 0.942 (35) (3 13 4). Chukochenite has a framework structure of spinel with low symmetry (orthorhombic Imma) due to the ordering of Li cations over octahedrally coordinated sites, which has not been previously reported for synthetic (Li0.5Al0.5) Al2O4. This structure type is based on a framework of AlO4 tetrahedra, AlO6, and LiO6 octahedra. AlO6 edge-sharing octahedra form chains along the a axis. AlO6 octahedra and LiO6 octahedra in a 2:1 ratio share edges, forming octahedral chains along b. These octahedral chains are connected by AlO4 tetrahedra and each corner of an AlO4 tetrahedron shares with three AlO6 octahedra or two AlO6 + one LiO6 octahedra. The discovery of chukochenite adds a new perspective on the cation ordering and the mechanism of luminescence and magnetism in (Li0.5Al0.5)Al2O4. [ABSTRACT FROM AUTHOR]