Mineralogical, geochemical, and spectral characteristics of low-high grade bauxite deposits of the southern bauxite zone at Al Ba’itha mine, Az Zabirah, Saudi Arabia

Abstract

Bauxite, the primary economic raw material for aluminum production, is extensively used due to its affordability. The Al Ba’itha mine in Az Zabirah, Saudi Arabia, contains bauxite deposits with varying textures, including pisolitic, oolitic, and oolitic-conglomeratic forms. Predominant minerals within these deposits include gibbsite, boehmite, and diaspore. These deposits have elevated concentrations of Al₂O₃ and Fe₂O₃, with average values standing at 53.59 wt% and 12.12 wt%, respectively. Minor constituents such as goethite, hematite, and boehmite contribute to these compositions. The presence of SiO₂ (average: 7.59 wt%) and TiO₂ (average: 2.94 wt%) suggests the existence of rutile, anatase, and kaolinite. To assess the grade and mineralogical composition of bauxite, spectra were obtained using the GER 3700 spectroradiometer across low, medium, and high-grade samples. Notable features in the spectra include strong Al–OH vibrations at wavelengths approximately 1.5, 2.2, and 2.3 µm, indicative of bauxite’s presence. The presence of hematite, goethite, and gibbsite is discerned through absorption features at 0.48 and 0.88 µm. Furthermore, absorption properties near 2.3 µm suggest the existence of calcite, attributed to the CO₃ molecule. Analysis of the Fourier-transform infrared (FTIR) spectrum of bauxite reveals absorption bands associated with kaolinite, hematite, quartz, and gibbsite. Integration of X-ray diffraction (XRD), FTIR, and reflectance spectroscopy was useful in determining bauxite grade and mineralogical composition. These methods serve as efficient tools in the exploration and characterization of bauxite deposits, facilitating informed decision-making in aluminum production processes.