Mineralogical and crystallographic characteristics of bauxites from some Grebnik’s (Metohija, Serbia) ore deposits

Abstract

Five typical bauxite samples from three ore deposits from the wider area of Grebnik Mt. (Metohija, Serbia) were examined with the optical microscopic, X-ray powder diffraction (XRPD) and chemical methods. The occurrences in bauxites were studied and described and the presence of major minerals was determined: diaspore, boehmite and hematite; minor minerals: quartz, goethite, rutile, kaolinite and hydro-hematite; as well as anatase, brookite, magnetite and chromite, which occur only sporadically. According to the quantity of main Al-bearers, three types of bauxite ore were recognized: diaspore, boehmite and boehmite-diaspore. Unit cell dimensions of major minerals were determined, mostly with values within reference data. However, all of the studied hematites have smaller a 0 and V 0 values, most probably due to the substitution of Fe 3+ by Al 3+. All samples are further classi ied as iron-rich and ferritic bauxites. It was found that there were changes in origin conditions between major Al-hydroxides minerals and hematite, as well as between the diaspore and boehmite. Determined chemical compositions put this raw material into high-quality raw materials for obtaining the electro corundum and alumina. The synthesis of the obtained data indicate that Grebnik's bauxites have some unique characteristics, more or less different from most of the World's known bauxite ore deposits.

Rietveld crystal structure refinement of a natural rhombohedral grossular-andradite garnet from Serbia

“…At the first sight, it is ob vi ous that the zones stud ied more or less dif fer from each other. Namely, unit cell di men -sions and vol umes (V 0 ), which were in our pre vi ous stud ies were al ready shown as use ful tools for ap prox i mate es ti ma tion of the Al-Fe 3+ sub sti tu tions in the oc ta he dral site (Tanèiae et al, 2012b;Cvetkoviae and Tanèiae, 2019), mostly in crease from zone A (core) to zones C and/or D, and then de crease in zones D and/or E (rim). For ex am ple, in the Ia63d space group there were cal cu lated Al sof's (Al calc ; from 59 to 66 at.%) on the ba sis of the de ter mined V 0 , and ac cord ing to the start ing data for Grs and Adr by Novak and Gibbs (1971).…”

Characterization, axial anisotropy and formation conditions of celestine minerals from the Jabal Eghei (Nuqay) volcanic province (southeastern edge of the Sirt Basin, southern Libya)

“…coe cients of the regression-R 2 (hereinafter correlations-C). These correlations, reported in our previous studies of bauxites and some other sulfate minerals (Cvetković and Tančić 2019;Tančić et al 2021) have proven themselves to be a very useful accessory tool, allowing comparison between various parameters. According to the results, the polynomial variations between the a 0 , c 0 and V 0 parameters are slightly better than the linear (Figure S6 in the ESM), suggesting the deviations from Vegard's law, which is in concordance with results of Goldish (1989) and Antao (2012).…”

“…Finally, the newly calculated unit-cell parameters are characterized on the basis of the apfu's (Table S11 in the ESM) and are presented in Table S15 in the ESM. The correlations between these a 0 , b 0 , c 0 and V 0 values, with those of the XRPD method (Table 4) having 0.884; 0.955; 0.959 and 0.936, respectively [C (14); Figure S22 in the ESM] have, in this case, a considerably good and signi cantly better correlation, than the previous one associated with this problematic [i.e. C (11); Table S9 and Figure S19 in the ESM].…”

Characterisation, axial anisotropy, and formation conditions of celestine minerals from the Jabal Eghei (Nuqay) late Neogene – Pleistocene volcanic province, southeastern edge of the Sirt Basin, southern Libya: Constraints on the mineralogical geothermometer

“…To examine these data and mutual correlations between the UCPs, we used MS Excel to calculate statistical parameters and the coefficients of the regression-R 2 (hereinafter correlations-C). These correlations, reported in our previous studies of different materials (Cvetković and Tančić, 2019;Tančić et al, 2021;Maksimović et al, 2023) are proven useful accessory tools, which allow the comparison between various parameters. According to the results, a polynomial regression between the a 0 , c 0 and V 0 parameters gives slightly better R 2 coefficients than linear regression (Supplementary Fig.…”

“…1e and Supplementary Fig. S1c) that is interconnected spatially with a southern-positioned Neogene to Quaternary segment of the famous Sirt basin; and (2) the Tibesti–Sirt arch or Jebel Eghei area (Rusk 2001; Cvetković et al , 2010, 2022; Kovačević et al , 2013; Radivojević et al , 2015; Elshaafi and Gudmundsson, 2016, 2017). Spatially, the Al Haruj province of Central Libya is in contact with the investigated southern-positioned Jabal Eghei Volcanic Province (Cvetković et al , 2010; Radivojević et al , 2015; Elshaafi and Gudmundsson, 2017; Fig.…”