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 a0 and V0 values, most probably due to the substitution of Fe3+ by Al3+. All samples are further classified 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.

Keywords

• Grebnik
• bauxites
• mineralogical
• crystallographic and chemical characteristics
• diaspore
• boehmite
• Al-hematite