Steel-making slag is largely used today in road construction and other applications, but significant volumes are landfilled and cannot be recycled for excessive contents in hazardous metals, such as chromium or vanadium. The long-term behaviour of this material is still little known, and the characterisation of large volume slag dumps remains an environmental challenge. In this study various analytical techniques are used to characterise Electric Arc Furnace (EAF) slag landfilled for several decades and exposed to chemical weathering and erosion. Coupling chemical, mineralogical and magnetic techniques helps to understand the relations between hazardous metals and mineral phases. A special interest is given to Fe-bearing minerals microstructure so as to link the magnetic properties of the material to its mineralogical composition. The studied slag presents high amounts of chromium (between 1 and 3 wt. %) and very high magnetic susceptibility values (near 60 × 10⁻⁶ m³/kg), explained by the presence of magnetite and a spinel solid solution. Some correlations are found between magnetic susceptibility and potentially hazardous metals, providing new perspectives for future environmental investigations.

Mine optimisation and anticipation of ore behaviour in the mineral processing and separation circuits are major economic drivers for all mining operations. Recent methodological developments with the inception of geometallurgy across multiple commodities have highlighted the importance of mineralogy in addition to elemental grades. In the last few decades, many quantitative tools have been developed, mostly SEM-based such as QEMSCAN^®, and used to provide the quantitative mineralogical compositions of samples. Their main drawback is the time and cost associated with sample preparation, acquisition time, and data QA/QC. The combined XRF-XRD of the SOLSA (Sonic On-Line drilling and Sampling Analysis) analytical solution brings a new methodology able to produce quantitative mineralogical and geochemical data at a speed compatible with a production environment. Its range of applications covers the entire life of a mining operation, from the initial exploration stage to mineral processing control, as well as waste management and environmental monitoring.

Mine optimisation and anticipation of ore behaviour in the mineral processing and separation circuits are major economic drivers for all mining operation. Recent methodological developments with the inception of geometallurgy across multiple commodities has highlighted the importance of mineralogy in addition to grades. Since several decades, many quantitative tools have been developed, mostly SEM-based such as QEMSCAN®, to provide quantitative mineralogical composition and textural properties of ore and gangue samples. We aim to compare the more established SEM-based techniques to the Solsa combined XRD-XRF analyser to highlight their respective potential and limitations depending on the minerals and goals of the mining operators. The combined XRF-XRD of the SOLSA analytical solution brings a new methodology able to produce quantitative mineralogical and geochemical data at a speed compatible with routine data collection, from exploration to quality control on the different streams of minerals in a processing plant.

Grande Côte Operations (GCO), a Senegalese subsidiary of the Eramet Group, specializes in the recovery of ilmenite, rutile, and zircon. The mine and its two processing plants have been in service since 2014. GCO is a major producer of titanium minerals, which are critical raw materials essential to a wide range of industrial ecosystems. Titanium is used in a variety of applications, including aerospace, defense, medical implants, and consumer products. In this study, we focus on the occurrence of relatively sulfur-bearing samples. high “Sulfur is a deleterious element that affects negatively the application in the welding rod industry) The sulfur concentration in one sample was up to 2%, which is much higher than the usual concentration of 0.05%. Automated mineralogy was used to assess the S-bearing mineral concentration, liberation, and texture to test processing means to extract or reduce the sulfur content. The sulfur is concentrated in framboidal pyrite, an iron sulfur mineral. The pyrite is well liberated indicating a potential to physically recover Sulfur. Processing could be done by density or by a combination of roasting and magnetic separation. It is the latter that is discussed here. The pyrite transforms into hematite at 600°C, roasting for an hour resulted in the transformation of all pyrite into hematite, a magnetic iron oxide. S was eliminated during roasting. The micromorphology of pyrite is pseudomorphically replaced by porous hematite displaying circular textures. Microcracks in the hematite particles are abundant and are interpreted as desulfurization channels of the original pyrite. Some of the pores in hematite mimic the original cubic shape of pyrite. The porous texture of hematite particles might lower the ideal density of these hematite particles. Hematite particles could be successfully removed from the samples by magnetic separation. Based on our findings, we suggest heating pyrite at 600°C for an hour and additional magnetic separation as a viable option for eliminating pyrite from the sample. However, further testing and optimization may be required to determine the feasibility of this process at a larger scale. Pyrite could also potentially be removed (together with zircon) at the density fraction >4.5 g/cm3 by dry density or air table separation. Our study demonstrates the power of automated mineralogy in identifying and quantifying deleterious elements and minerals in complex samples originating from mining operations. By adding textural information, potential process options to remove these minerals and elements can be suggested.