Bauxite is a lateritic mineral deposit rich in aluminium and potentially rich in Rare Earth Elements. It has economic significance and provides insights into paleoenvironmental and paleoclimatic conditions. The thesis aims to characterize the mineralogical and geochemical properties of bauxite deposits in Košute and Gljev, once-active bauxite mines in the vicinity of the town of Sinj. In order to determine mineralogical composition, samples are analysed with optical methods and X-ray powder diffraction (XRPD). Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) is employed for chemical analysis and Inductively Coupled Plasma Spectroscopy with mass spectrometry (ICP-MS) is used to determine the bulk chemical composition of the samples. Both karstic bauxite deposits lie on Upper Cretaceous limestones and are covered by Paleogene Promina carbonate beds. Bauxites from Košute are gibbsitic and contain 24% of silica while the bauxites from Gljev are boehmitic to gibbsitic and present the most exploitable bauxites in the vicinity of Sinj. They exhibit a high Al:Si ratio, reaching up to 18:1. The samples from Gljev show total REE abundances up to 1500 ppm with LREE enrichment. Some Gljev samples exhibit elevated concentrations of yttrium, leading to higher concentrations of HREE. The La/Y ratio in Košute suggests alkaline weathering conditions (2.33-2.37) and that in the samples from Gljev to acidic conditions (0.60-0.85). REE-bearing minerals are monazite and zircon but REEs are likely also absorbed on clay minerals.