Mineralogical and thermal characteristics of low-grade Jinlong bauxite sourced from Guangxi Province, China

Characteristic samples from the No. 1 ore body of the Jinlong bauxite deposit in Guangxi Province, China, were assessed to determine their chemical composition using whole-rock geochemical analysis, their mineral components using X-ray diffraction, their thermal characteristics via differential thermal analysis, thermogravimetry and differential thermogravimetry, and their dissemination characteristics by scanning electron microscopy/energy-dispersive spectrometry. The results show that the average Al2O3 content in the Jinlong bauxite deposit is 41 % and that the Al2O3/SiO2 ratio is approximately 2.17, and thus, the ore may be defined as low-grade bauxite. The main minerals found in the ore were diaspore (20.3-43 %), gibbsite, clays and hematite. In differential thermal analysis results, the bauxite samples exhibit two distinct endothermic peaks, with the dehydration of gibbsite occurring in the 200-260 A degrees C range and the dehydration of diaspore occurring in the 524-550 A degrees C range. Thermogravimetry and differential thermogravimetry indicate four decomposition stages: evaporation of adsorbed water (50-160 A degrees C), gibbsite decomposition (190-280 A degrees C), goethite decomposition (190-280 A degrees C) and diaspore dehydroxylation (460-580 A degrees C). The diaspore belongs to the orthorhombic dipyramidal class and exists primarily in three dissemination forms-euhedral and subhedral grain, bean and oolitic shaped, and aphanitic and microcrystalline aggregates, and is always accompanied by kaolinite and pyrophyllite.