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The elastic and structural behaviour of the synthetic zeolite CsAlSi 5 O 12 (a = 16.753(4), b = 13.797(3) and c = 5.0235(17) A ˚, space group Ama2, Z = 2) were investigated up to 8.5 GPa by in situ single-crystal X-ray diffraction with a diamond anvil cell under hydrostatic conditions. No phase-transition occurs within the P-range investigated. Fitting the volume data with a third-order Birch-Murnaghan equation-of-state gives: V 0 = 1,155(4) A ˚3, K T0 = 20(1) GPa and K 0 = 6.5(7). The ''axial moduli'' were calculated with a third-order ''linearized'' BM-EoS, substituting the cube of the individual lattice parameter (a 3 , b 3 , c 3 ) for the volume. The refined axial-EoS parameters are: a 0 = 16.701(44) A ˚, K T0a = 14(2) GPa (b a = 0.024(3) GPa -1 ), K 0 a = 6.2(8) for the a-axis; b 0 = 13.778(20) A ˚, K T0b = 21(3) GPa (b b = 0.016(2) GPa -1 ), K 0 b = 10(2) for the b-axis; c 0 = 5.018(7) A ˚, K T0c = 33(3) GPa (b c = 0.010(1) GPa -1 ), K 0 c = 3.2(8) for the c-axis (K T0a :K T0b :K T0c = 1:1.50:2.36). The HP-crystal structure evolution was studied on the basis of several structural refinements at different pressures: 0.0001 GPa (with crystal in DAC without any pressure medium), 1.58(3), 1.75(4), 1.94(6), 3.25(4), 4.69(5), 7.36(6), 8.45(5) and 0.0001 GPa (after decompression). The main deformation mechanisms at high-pressure are basically driven by tetrahedral tilting, the tetrahedra behaving as rigid-units. A change in the compressional mechanisms was observed at P B 2 GPa. The P-induced structural rearrangement up to 8.5 GPa is completely reversible. The high thermo-elastic stability of CsAlSi 5 O 12, the immobility of Cs at HT/HP-conditions, the preservation of crystallinity at least up to 8.5 GPa and 1,000°C in elastic regime and the extremely low leaching rate of Cs from CsAlSi 5 O 12 allow to consider this openframework silicate as functional material potentially usable for fixation and deposition of Cs radioisotopes.

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The economic significance of pegmatites as a source of strategic rare metals for high-tech products and green energy motivated the present study on Ta–Nb oxides from Vishteritsa rare-element beryl–columbite LCT pegmatites of the Rila–West Rhodopes Batholith in the Western Rhodopes, Bulgaria. Here, we present the first U/Pb age data from columbite with application of the LA–ICP–MS U–Pb technique and a new X36 columbite standard reference material. The obtained Concordia age of 47.57 ± 0.32 Ma with a small spread of the individual 206Pb/238U ages between 45 and 51.3 Ma argues for Early Eocene magmatism and pegmatite formation. The host granite of the rare-element pegmatites is dated 51.94 ± 0.61 Ma with LA–ICP–MS U–Pb technique on zircon and suggests a fertile Early Eocene magmatic period in the Western Rhodopes. EPMA data for the composition of the columbite is used to refine the formula of the mineral (Mn0.554Fe0.427U0.006)0.987(Nb1.826Ta0.085Ti0.116)2.03O6 and define it as columbite-(Mn). Application of the in-situ LA–ICP–MS data technique establishes a series of typical trace elements (Ti, U, Zr, Hf, Y, W, and Zn) that are usually found in content above 500 ppm. The studied columbite is enriched in heavy rare earth elements (HREE sum: 306–697 ppm) and depleted in light REE and Eu. These geochemical characteristics are collectively interpreted as evidence for crystallization from highly fractionated fluid-rich magma. High UO2 content reaching 0.89 wt. % is characteristic for the Vishteritsa columbite. The decrease of U proximal to cracks and in outer crystal zones documents U-mobility during overprinting hydrothermal processes.

Samples of scapolite from the marble quarry from the Samurski Dol locality, situated nearby Chepelare, Central Rhodopes, Bulgaria have been subjected to chemical analyses and single crystal X-ray diffraction studies. The obtained values for the meionite component (Me) range between 70 and 75. The crystal structure of the studied sample has been solved in both I4/m and P42/n space groups, traditionally assigned to scapolite members. The paper provides new insight on the choice of correct space group for description of scapolites crystal structures, with a view of the preferred positions by silicon and aluminum ions and their framework ordering.

The current study presents the electron beam melting (EBM) efficiency of copper technogenic material with high impurity content (Se, Te, Pb, Bi, Sn, As, Sb, Zn, Ni, Ag, etc.) by means of thermodynamic analysis and experimental tests. On the basis of the calculated values of Gibbs free energy and the physical state of the impurity (liquid and gaseous), a thermodynamic assessment of the possible chemical interactions occurring in the Cu-Cu2O-Mex system in vacuum in the temperature range 1460–1800 K was made. The impact of the kinetic parameters (temperature and refining time) on the behaviour and the degree of removal of impurities was evaluated. Chemical and metallographic analysis of the obtained ingots is also discussed.

Fully exchanged Ag-clinoptilolite prepared at 100°C using 1 M solution of AgNO3 was studied. The initial sample (Beli Plast deposit, Bulgaria) was enriched in clinoptilolite by a sequence of treatments – crushing, sieving, sedimentation, and separation with heavy liquids to obtain a content of about 93 wt.% of clinoptilolite intergrown with opal-C. Opal-C was subsequently removed by chemical treatment. Maximum cation exchange was reached on the seventh day (4.86(4) Ag atoms per formula unit). Rietveld structural refinement was then carried out on the Ag-exchanged clinoptilolite, and three independent Ag sites were localated in the channels of the clinoptilolite structure. Seven water sites, coordinating the Ag sites, were located. Ag-clinoptilolite is, potentially, a promising low-cost antibacterial material.