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Bauxite samples from the three ore deposits from the wide territory of Grebnik Mt. (SW Serbia) were examined with the microscopic, X-ray and chemical methods. Their common characteristics are that they represent massive compact rocks with clear visible oolites and pisolites with size of 0.5-0.8 cm. Besides oolites, there were noticed plenty of small angular fragments of clay material and biggest fragments of the sedimentary bauxites which are of similar structure as the main rock, but with somewhat brightness color. Determined mineral composition by its relative quantity is: boehmite, diaspore, hematite and hydro-hematite which dominate and small quantity of limonite-goethite, quartz, rutile and kaolinite. Three types of the bauxite ore were established: boehmite, diaspore and boehmite-diaspore type. Hematite is mostly in mass shapes which were resulted from the hydro-hematite transformation and also in fine disperse particles which penetrated the whole aluminum-hydroxide basis and simultaneously pigments it. It is also present as oolitic grains which are fresh or transformed into limonite, while small crystals are mostly broken and like this cemented in the bauxite basis. Locally it is present in small accumulations and covered with fine disperse limonite, so it looks like honey-comb and vein structure. Hydro-hematite is mostly present as bespattered and oolite grains with different dimensions. Oolites and pisolites are also cemented in the aluminum-hydroxide basis. Beside fresh hydro-hematite grains, there are also present grains which were transformed into limonite.
In some oolites it is clear zonal exchanging of hydro-hematite with limonite, and somewhere there is present zonal separation of hematite in the big oolite grains of hydro-hematite. Big oolites, macroscopic visible, build from number of little oolites of the hydro-hematite and hematite composition and in fractures of this big oolites aluminum hydroxides are deposited. Limonitization is mostly performed in the central parts of the oolites. A small part appears as mass shapes of different sizes which are most often resulted from transformation of hematite. High content of Al2O3 (45.35-57.60%) and relatively low content of SiO2 (1.98-8.40%), put this material into the high-quality materials for obtaining the electro corundum and alumina. The Fe2O3 content vary from 23.10% to 39.60%; TiO2 from 3.84% to 4.61%; and CaO from 0.07% to 0.26%.
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