Mineralogy and crystallographic properties of heu-type zeolitic tuff from the novakovic deposit, Bosnia and Herzegovina

This paper presents mineralogical and crystallographic characterization of the zeolitic tuff from the Novakovic deposit, Republic of Bosnia and Herzegovina. The zeolitic tuff is of a whitish color composed of Ca-clinoptilolite and an amorphous phase (volcanic glass and amorphous SiO 2 ). The zeolitic tuff was analyzed by X-ray diffraction of the polycrystalline sample (XRPD), scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), and differential thermal and thermogravimetric (DTA/DTG) methods. According to the results obtained, it can be concluded that the studied zeolitic tuff is composed of Heu-type minerals. Based on the chemical analysis, thermal treatment and XRPD analysis it was determined that this is a mineral Ca-clinoptilolite. Thermal analysis in the temperature range from 300 up to 700°C showed that the examined zeolite minerals from the Novaković deposit are stable up to the temperature of 600°C. The crystal structure of Ca-clinoptilolite has been refined in the centrosymmetric space group C2/m (S.G. 12) with disordered distribution of Al and Si in the tetrahedral framework. The unit-cell parameters are as follows: a = 17.662 Å, b = 17.874 Å, c = 7.402 Å, β = 116.32° and V = 2122.73 Å 3 . The basic structural motif is represented by four channels. Three channels are composed of eight-membered rings, and one of ten-membered rings. The ten-membered (channel A) and one eight-membered channel (B) are parallel to the crystallographic axis c, and the other eight-membered channel is parallel to the a-axis. Ca-clinoptilolite comprises approximately 90 % of the studied zeolite tuff while the rest 10 % is the amorphous phase. The overall cation exchange capacity (CEC) amounts to 187 mmolM + / 100 g, and calcium represents the most abundant cation in the studied sample. The atomic ratios of Si/Al, Na + /(Na + +K + ), and Ca 2+ /(Ca 2+ +Mg 2+ ) are as follows: 4.36, 0.14, and 0.55, respectively. The zeolite tuff is both thermally and structurally stable and has applications in various areas of industry and agriculture. © 2018, Association of Chemists and Chemical Engineers of Serbia. All rights reserved

Mineralogy and crystallochemical characteristics of HEU-type minerals from zeolitic tuff deposits of Serbia

The results of perennial research of several Serbian zeolitic tuffs enriched with HEU-type minerals are presented in this paper. There are several recognized zeolitic tuff deposits containing HEU-type minerals: Zlatokop, Igroš, Beočin, Toponica, Slanci, but their comparative mineralogical and crystallochemical features have not been studied in detail so far. These zeolitic tuff deposits are spatially and genetically connected to volcanic and pyroclastic rocks of marine and lake environments of Senonian and Eocene, and Neogene age, respectively. As a result of devitrification and diagenesis process of volcanic glass within zeolitic tuffs hypocrystalline porphiry and vitroclastic textures occur. The studied zeolitic tuffs are mainly composed of heulandite occuring in a form of needle- to plate-like crystals of 0,1 do 100 μm in length, associated with other silicates. Depending on the type and content of exchangeable cations as well as the thermal stability of these raw materials, 24 clinoptilolite-Ca and heulandite-Ca can be distinguished. The values of cation exchange capacity and surface area capacity range from 96 to 166 meq/100 g, and from 8,0 to 10,5 meq/100 g, respectively. HEU-type minerals can be distinguished either by a Si/Al ratio or arrangement of extra framework cations within the crystal structure of these minerals. [Projekat Ministarstva nauke Republike Srbije, br. TR 34013: Osvajanje tehnoloških postupaka dobijanja ekoloških materijala na bazi nemetaličnih mineralnih sirovina i br. 45012: Sinteza, procesiranje i karakterizacija nano strukturnih materijala za primenu u oblasti energije, mehaničkog inţenjerstva, zaštite životne sredine i biomedicine

THE CRYSTALLIZATION OF POTASSIUM GERMANATE GLASS WITH HIGH CONTENT OF NIOBIUM OXIDE

Potassium germanate glass with molar ratio [GeO2]/[K2O] = 1.2 and Nb2O5 content of 34 mol% have been synthesized by a melt-quenching method. The crystallization behavior under non-isothermal and isothermal crystallization conditions was investigated. The results showed that this glass exposed complex primary crystallization. In the temperature range 800 °C. K10Nb22Ge4O68 and metastable KNbO3 and K4Nb6O17 were formed as secondary phases. The crystallization commenced at T > 640 °C with high homogeneous nucleation rate and spherulite crystal growth morphology. DTA curves recorded for powder samples particle size 0.1 mm showed two exothermic peaks and two endothermic peaks within temperature range of T = 640-1020 °C. The analysis of the dominant crystallization mechanism of powder glass sample and kinetics of crystallization is presented

A review of Pb-Sb(As)-S, Cu(Ag)-Fe(Zn)-Sb(As)-S, Ag(Pb)-Bi(Sb)-S and Pb-Bi-S(Te) sulfosalt systems from the Boranja orefield, West Serbia

Recent mineralogical, chemical, physical, and crystallographic investigations of the Boranja orefield showed very complex mineral associations and assemblages where sulfosalts have significant role. The sulfosalts of the Boranja orefield can be divided in four main groups: (i) Pb-Sb(As)-S system with ±Fe and ±Cu; (ii) Cu(Ag)-Fe(Zn)-Sb(As)-S system; (iii) Ag(Pb)-Bi(Sb)-S; (iv) and Pb-Bi-S(Te) system. Spatially, these sulfosalts are widely spread, however, they are the most abundant in the following polymetallic deposits and ore zones: Cu(Bi)-FeS Kram-Mlakva; Pb(Ag)-Zn-FeS2 Veliki Majdan (Kolarica-Centralni revir-Kojići); Sb-Zn-Pb-As Rujevac; and Pb-Zn-FeS2-BaSO4 Bobija. The multi stage formation of minerals, from skarnhydrothermal to complex hydrothermal with various stages and sub-stages has been determined. All hydrothermal stages and sub-stages of various polymetallic deposits and ore zones within the Boranja orefield are followed by a variety of sulfosalts. [Projekat Ministarstva nauke Republike Srbije, br. OI-176016: Magmatism and geodynamics of the Balkan Peninsula from Mesozoic to present day: Significance for the formation of metallic and non-metallic mineral deposits

Badanie możliwości otrzymywania koncentratu poflotacyjnego zawierającego mikę ze skaolinizowanego granitu

This study shows the results of flotation concentration of mica minerals from kaolinised granite taken from the "Bašića bare" deposit – Kobaš, Srbac, The Republic of Srpska (B&H). Mineralogical composition of kaolinised granite is as follows: kaolinite, feldspar, quartz, and mica. After separating >0.630 mm, and 0.630 mm i <0.043 mm, zawierających największe ilości kaolinitu, pozostały produkt stanowi klasa ziaren o wymiarach –0.630+0.043, zawierających kwarc, skaleń oraz mikę. Koncentrat zawierający mikę otrzymano z koncentratu poflotacyjnego, skaleń i kwarc zebrano w produkcie dolnym procesu flotacji. W oparciu o analizy składu mineralogicznego stwierdzono, że minerałami występującymi w największych ilościach są mika oraz chloryty/iły, kwarc oraz skalenie wy-stępują w znacznie mniejszych ilościach podczas gdy pozostałe minerały występują jedynie w ilościach śladowych. Przeprowadzona analiza mineralogiczna koncentratu miki w ujęciu ilościowym w oparciu o wyniki rentgenowskiej dyfraktometrii proszkowej (X-ray powder diffraction – XRPD) ujawniła że skład jego jest następujący: mika ≈55%; chloryty/iły ≈35 %; kwarc ≈5%; skalenie (łącznie plagioklazy i skalenie potasowe) ≈5%

Preparation of glass-ceramic in Li2O-Al2O3-GeO2-P2O5 system

The results of preparation and structural characterization of glass-ceramics from the system Li2O-Al2O3-GeO2-P2O5 are shown in this paper. The crystallization behaviour of the selected glass was examined under non-isothermal and isothermal crystallization conditions. DTA, XRD and SEM methods were employed for analyses. It was confirmed that this glass crystallizes by the volume crystallization mechanism. The results also showed that the glass crystallize by primary crystallization. As a primary phase the LiGe2(PO4)3 is formed and the traces of GeO2 as a secondary one is present. The crystallization process occurred at a high homogeneous nucleation rate and the spherical morphology of crystal growth. By applying the Kissinger relation the activation energy of crystal growth Ea = 462 kJ/mol was determined

Crystallization behaviour of Li2O·Nb2O5·SiO2 glass containing TiO2

This paper deals with the crystallization of glass 30Li2O·15Nb2O5·50SiO2·5TiO2 (mol%). The crystallization behaviour was studied under isothermal and non-isothermal conditions. XRD and SEM methods were employed for determination of phase composition and microstructure of crystallized glass. It was detected that this glass crystallizes by the surface crystallization mechanism. SEM micrographs of the crystallized samples revealed that the crystals grow in the form of dendrites. The glass-ceramics with complex phase composition was obtained. Three crystalline phases were detected where LiNbO3grown as primary phase and a secondary ones Li2Si2O5 and SiO2 appeared. The calculated average crystallite sizes are: 27 nm for LiNbO3, 115 nm for Li2Si2O5 and 45 nm for SiO2. From the experimental data an activation energy of crystals growth, calculated using the Kissinger relation, is Ea = 275 ±10 KJ / mol

Crystal growth of la(2)srb(10)o(19)from undercooled melt

The crystal growth rate of La(2)SrB(10)O(19)in an undercooled melt of stoichiometric composition was studied. The crystallization of the bulk samples was performed in a single-stage regime under isothermal conditions at the selected temperatures for the different time periods. The surface crystallization was observed and in all crystallized samples, the La(2)SrB(10)O(19)crystalline phase was identified. Based on the dependence of the crystalline layer thickness on treatment time at selected temperature, crystal growth rate was obtained. The crystal growth rates were from 1.65 x 10(-8)to 2.77 x 10(-7)m s(-1)in the temperature interval (700-780 degrees C). The experimental values were compared to the calculated values using theoretical model of the crystal growth. The experimental growth rate followed the same trend as the calculated growth rate, but the experimental values were higher than the calculated

Investigation of thermally induced processes in corundum refractory concretes with addition of fly ash

The effects that the fly ash addition has on the behavior of thermally resistant corundum concrete were discussed. Experimental program implied production of two refractory composites: "referent" concrete from 20 % of high-aluminate cement and 80 % of corundum aggregate, "recycled" concrete from 10 % of high-aluminate cement, 20 % of lignite coal ash, and 70 % of corundum aggregate. The fly ash was mechanically activated by a vibratory disk mill. In the concrete matrix, the ash had a role of cement partial replacement and microfiller. The mechanical and thermal properties of the concretes were studied at temperatures ranging from ambient to 1,400 A degrees C as adopted maximum. Mechanisms of thermally induced processes were observed by differential thermal analysis at 10, 20, and 30 A degrees C min(-1) heating rates. Referent and recycled concretes showed differences in calculated activation energies. The variations in refractory concretes performances were discussed with support of scanning electron microscope imagining and X-ray diffraction results. The recycled ash concrete exhibited properties that met the requirements for the castables, which proves it suitable for use in severe conditions at high temperature and highlights the reusing principle and possibility of cleaner and economically sustainable production