Process mineralogy of rare earths from deeply weathered alkali-carbonatite deposits in Brazil

Abstract

Brazil has the second largest rare earths mineral (REM) resource in the world, mainly associated with the weathered portion of carbonatite complexes. This paper reports process mineralogy studies performed for 10 samples collected from the deeply weathered portion of different relevant Brazilian deposits, having a soil appearance and varied grain sizes with a significant content of natural fines (below 20 μm). The results indicate that REM are mainly composed of light rare earth elements and present a fine-grained nature and intricate associations with gangue minerals. Monazite is by far the most relevant REM; cerianite and bastnaesite are typical of only one of the studied deposits. The complexity of the occurrence of the rare earths challenges the development of mineral processing routes. A scandium phosphate mineral identified as a trace in one of the studied deposits has not yet been reported in the Brazilian alkaline complexes.