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Nickolayite, FeMoP, is a new terrestrial phosphide structurally related to allabogdanite (high-pressure modification of (Fe,Ni)2P), and the meteoritic phosphides florenskyite, FeTiP and andreyivanovite, FeCrP. From the point of view of chemical composition, nickolayite is an Fe-analogue of monipite, MoNiP. The mineral was discovered in the Daba-Siwaqa complex, Central Jordan, a part of the pyrometamorphic Hatrurim Formation (the Mottled Zone), whose outcrops encompass a 150 × 200 km area around the Dead Sea in the Middle East. Nickolayite appears as an accessory phase in the fused clinopyroxene–plagioclase rocks texturally resembling gabbro–dolerite. The irregularly shaped grains of the mineral, up to 80 μm in size are associated with baryte, tridymite, chromite, hematite, pyrrhotite, fluorapatite, titanite and powellite. Macroscopically, nickolayite grains possess light-grey to greyish-white colour and metallic lustre. The mineral is ductile. The mean VHN hardness (50 g load) is 538 kg mm–2. The calculated density based on the empirical formula and the unit-cell parameters is 7.819 g cm–1. In reflected light, nickolayite has a white colour, with no bireflectance or pleochroism. The COM approved reflectance values [Rmax/Rmin (%), λ(nm)] are: 48.5/46.5 (470), 50.5/48.5 (546), 51.8/49.9 (589) and 53.9/52.0 (650). The chemical composition of the holotype crystal is (electron microprobe, average of 4 analyses, wt.%): Fe 32.21, Mo 47.06, Ni 3.69, Co 0.13, P 17.45, total 100.54, that corresponds to the empirical formula Fe1.00(Mo0.87Ni0.11Fe0.02)Σ1.00P1.00 and an ideal formula of FeMoP. Nickolayite is orthorhombic, space group Pnma, unit-cell parameters of holotype material are: a = 5.9519(5), b = 3.7070(3), c = 6.8465(6) Å, V = 151.06(2) Å3 and Z = 4. The crystal structure of holotype material was solved and refined to R1 = 0.0174 based on 251 unique observed reflections. The origin of the mineral is probably connected to the processes of co-reduction of molybdenum- and phosphorus-bearing minerals during high-temperature pyrometamorphic processes.
Dargaite, ideally BaCa12(SiO4)4(SO4)2O3, is an additional member of the arctite group belonging to minerals with a modular intercalated antiperovskite structure derived from hatrurite. The holotype specimen was found at a small outcrop of larnite pseudoconglomerates in the Judean Mts, West Bank, Palestinian Autonomy. Larnite, fluorellestadite–fluorapatite, brownmillerite, fluormayenite–fluorkyuygenite and ye'elimite are the main minerals of the holotype specimen; ternesite, shulamitite and periclase are noted rarely. Dargaite, nabimusaite and gazeevite occur in linear zones with higher porosity within larnite rocks. Pores are filled with ettringite and Ca-hydrosilicates, less commonly with gibbsite, brucite, baryte, katoite and calciolangbeinite. Dargaite is colourless, transparent with a white streak and has a vitreous lustre. It exhibits pronounced parting and imperfect cleavage along (001). Mohs’ hardness is ~4.5–5.5. The empirical formula is (Ba0.72K0.24Na0.04)Σ1(Ca11.95Mg0.04Na0.01)Σ12([SiO4]0.91 [PO4]0.05[AlO4]0.03[Ti4+O4]0.01)Σ4([SO4]0.84[PO4]0.14[CO3]0.02)Σ2(O2.54F0.46)Σ3. Dargaite is trigonal R$\overline 3 $m, the unit-cell parameters are: a = 7.1874(4) Å, c = 41.292(3) Å, V = 1847.32(19) Å3 and Z = 3. The crystal structure of dargaite was refined from X-ray single-crystal data to R1 = 3.79%. The calculated density is 3.235 g cm–3. The following main Raman bands are distinguished on the holotype dargaite (cm–1): 122, 263, 323, 464, 523, 563, 641 and 644, 829 and 869, 947, 991 and 1116. The formation conditions of dargaite are linked to the local occurrence of pyrometamorphic by-products (gases, fluids and melts) transforming earlier mineral associations at ~900°C.
Dzierżanowskite, , a thiocuprate, was found in larnite pseudoconglomerate rocks of the Hatrurim Complex at Jabel Harmun, Palestinian Autonomy, Israel. Dzierżanowskite occurs in larnite pebbles, which are embedded in a low-temperature mineral matrix. Associated minerals are larnite, brownmillerite, fluorellestadite, ye'elimite, gehlenite, periclase, ternesite, nabimusaite, vorlanite, vapnikite, fluormayenite, fluorkyuygenite, oldhamite, jasmundite, covellite, chalcocite and pyrrhotite. Electron microprobe analyses yield an average composition of Cu 55.25, Fe 0.13, S 27.46 and Ca 16.99, total 99.83 wt.%. The empirical formula of dzierżanowskite, based on 5 atoms, is Ca0.98Cu2.02Fe0.01S1.99. Dzierżanowskite forms grains up to 15 μm in size or rims on oldhamite and laminar intergrowths with chalcocite and covellite. Dzierżanowskite is dark orange, has a cream streak and a submetallic lustre. In reflected light it is grey, with a cream tint and characteristic yellow-orange internal reflections. The calculated density of dzierżanowskite is 4.391 g cm -3. Three bands at 300, 103 and 86 cm -1 are observed in the Raman spectrum. The strongest lines of the calculated powder diffraction pattern are [d, Å (I) hkl]: 2.358(100) 102, 1.970(93)110, 3.023(78) 011, 6.523(36) 001, 3.412 (28) 100, 1.834(28) 103. Dzierżanowskite was also found in unusual jasmundite rocks, forming small ‘paleofumaroles’ within areas of low-temperature hydrothermal rocks bearing larnite pseudoconglomerates at Jabel Harmun. Dzierżanowskite is a superimposed phase of the high-temperature alteration of pyrometamorphic rocks subjected to by-products (melts/fluids and gases) of pyrometamorphism originating in the deeper levels of combustion.
Two new barium-bearing minerals: gurimite, Ba3(VO4)2 (IMA2013-032) and hexacelsian, BaAl2Si2O8 (IMA2015-045) were discovered in veins of paralava cutting gehlenite-flamite hornfels located in the Gurim Anticline in the Negev Desert, Israel. Gurimite and hexacelsian occur in oval polymineralic inclusions in paralava and are associated with gehlenite, pseudowollastonite or wollastonite, rankinite, flamite, larnite, schorlomite, andradite, fluorapatite, fluorellestadite, kalsilite, cuspidine, aradite, zadovite and khesinite. Gurimite and hexacelsian form elongate crystals <10 μm thick. The minerals are colourless and transparent with a white streak and vitreous lustre, and have (0001) cleavage, respectively good in gurimite and very good in hexacelsian. Fracture is irregular. Density calculated using empirical formulas gave 5.044 g cm–3 for gurimite and 3.305 g cm–3 for hexacelsian. Mean refractive indexes, 1.945 and 1.561, respectively, were also calculated using the empirical formulas and the Gladstone-Dale relationship. The minerals are uniaxial and nonpleochroic. The following empirical crystal chemical formulae were assigned to holotype gurimite: (Ba2.794K0.092Ca0.084Na0.033Sr0.017)∑3.020(V1.8275+S0.0916+P0.0515+Al0.040Si0.005Fe0.0053+)∑2.017O8,and holotype hexacelsian: (Ba0.911K0.059Ca0.042Na0.010)∑1.022Al1.891Fe0.0723+Si2.034O8. The Raman spectrum of hexacelsian is similar to the one of the synthetic disordered β-BaAl2Si2O8. The Raman spectrum of gurimite is identical to that of synthetic Ba3(VO4)2. The electron back-scattered diffraction (EBSD) pattern of gurimite was fitted to the structure of its synthetic analogue with the cell parameters of R3m, a = 5.784(1),c = 21.132(1) Å, V = 612.2(2) Å3, Z = 3, giving a mean angular deviation = 0.43° (good fit). The Raman spectra of hexacelsian and its EBSD pattern suggest that natural hexacelsian corresponds to disordered synthetic β-hexacelsian P63/mcm, a = 5.2920(4) Å, c = 15.557(2) Å, α = β = 90°, γ = 120°. We suggest that after relatively fast crystallization of the main constituents of the paralava, gurimite, hexacelsian and also other Ba-bearing phases crystallized from residual melt enriched in incompatible elements that filled interstices between crystals of the main constituents.
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