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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A theory of the thermally stimulated current (TSC) transport peak, developed recently, predicts thickness dependence of the maximum temperature of the peak. The experimental observation of this effect, found for the high-temperature TSC peak in poly(N4nylcarbazole) is presented and discussed in terms of dispersive transport.

For the first time, the photoluminescence of ions of Ce 3+ and Eu 2+ in natural low-P ternesite has been measured. The emission bands of Ce 3+ ions at 405, 426, and 440 nm and the corresponding excitation wavelengths suggest the presence of Ce 3+ ions in three different cationic sites. In the photoluminescence spectra of Eu 2+ , emission bands at 530 and 620 nm can be seen that originate from two different cationic sites. In addition, it is demonstrated that an energy transfer occurs between Ce 3+ and Eu 2+ ions situated in those cationic sites where the force of the crystallic field is weakest. The photoluminescence spectra were obtained for a thin section sample with low contents of these two elements (41.2 ppm Ce, 2.11 ppm Eu).