Investigation of cassiterite and columbite ores: development and optimisation of processing technologies

On behalf of the Federal Institute for Geosciences and Natural Resources and the German Mineral Resources Agency, G.E.O.S. developed an economically more efficient extraction method for the tin mineral cassiterite and the by-products columbite-tantalite for tantalum and niobium extraction as well as other valuable minerals from sedimentary deposits in the Rondônia/Brazil region.

In addition, the radioactively contaminated minerals were identified and an effective strategy for separating them from the sample material was developed. The placers were processed using finely tuned gravimetric and magnetic methods. Adapted technologies were used to achieve the required concentration of valuable minerals and the separation of radioactive minerals. Particular emphasis was placed on the economic efficiency and environmental compatibility of these separation processes.

G.E.O.S. was responsible for sample preparation and sample processing:

• Gravimetric separation of the heavy minerals using heavy liquids
• Enrichment of the valuable minerals by density separation on the wet hearth (semi-technical)
• Mineralogical analysis of the heavy and light fractions by XRD, SEM-EDX
• Optical and mineralogical assessment of the fractions (intergrowths)
• Magnetic separation using various magnetic separation methods (ribbon, Frantz separator into ferro-, para- and diamagnetic fractions)
• Production of various concentrates (cassiterite, columbite-tantalite, monazite, zircon)
• Quantitative and semi-quantitative chemical analysis of all fractions with handheld XRF
• Measurement of radiation intensity as local dose rate, alpha, beta+gamma radiation
• Mineralogical-geochemical identification of the radioactive minerals
• Economic analyses and recommendations for action