Automated mineralogy as a key technology toward zero-waste mining – The EXCEED project

The increasing demand for critical raw materials (CRMs) linked to the energy transition, Europe’s reliance on a few third countries (incl. China) for the supply of these combined with increased ESG issues calls for a new mining paradigm: i.e., responsible, zero-waste, multi-metal/mineral mining. Li-hard rock deposits (pegmatites and rare-metal granites) are perfect candidates for such an approach, where, besides lithium, numerous by-products including industrial minerals (quartz, feldspar, micas) and CRMs (Nb, Ta, and so forth) could be potentially extracted. To assess whether these by-products can be recovered during Li production requires a mineral-centric, integrated geometallurgical approach. Automated mineralogy is a key technology for such an approach. Determining how to utilize the secondary material streams and recovery of the by-products relies on the knowledge of the material, its chemical composition, particle size, crystal structure and texture to grain size, liberation grade and mineral associations. In this study, four European lithium mine projects, two pegmatite projects (Keliber, Finland and Savannah, Portugal) as well as two rare-metal granite (RMG) projects (Beauvoir, France and St Austell, UK), are investigated. Different ore types as well as process samples (concentrates, residues, and tailings) were investigated to assess the by-product potentials of industrial minerals, CRM’s as well as the status and behavior of potentially harmful elements (PHEs) throughout the processing flowsheet. Gathering of all this information is started by the Extended BSE Liberation Analysis (XBSE_STD) and Grain-Based X-ray Mapping (GXMAP) measurements with the FEI Quanta 650F, an automated Scanning Electron Microscope equipped with a field emission gun electron source, two Energy Dispersive X-ray spectrometers (EDX) (Bruker X-Flash 6130), and FEI’s Mineral Liberation Analyzer (MLA) quantitative mineralogy software v. 3.1.4. Additional data is collected with Micro-XRF Bruker M4 Tornado plus with AMICS. Details are further studied with additional methods, such as X-ray powder diffraction, Inductively Coupled Plasma Optical Emission spectroscopy, Electron Probe Micro-Analyses, Laser ablation ICP-MS, and X-ray Fluorescence measurements.  

To define how the ore properties and the PHE/CRM deportment affect the options for usability, a comprehensive geometallurgical assessment will be conducted starting from collecting the basic mineralogical data to creating process flowsheet options and predicting theoretical process performance. These results are then to be tested at the lab and pilot scale according to the produced process protocols to be validated.