Characterization of mineralogical impurities in a carbonate-rich material using MLA

• MLA enables detailed analysis of mineral impurities in calcite materials. • Low liberation of impurities challenges traditional separation techniques. • Particle shape impacts sedimentation, mobility, and separation stability. • Concentration criterion suggests centrifugal methods for better purification. This study highlights the effectiveness of the Mineral Liberation Analyzer (MLA) in characterizing mineralogical impurities within high-grade calcite material. The paper presents detailed quantitative and qualitative data on mineral composition, liberation, associations, and particle shape indicators such as aspect ratio, circularity, and angularity. These observations allow for the development of more effective processing strategies to improve purity and color, which are key aspects in separation and purification processes. The results reveal that the primary impurities are orthoclase, quartz, plagioclase, biotite, titanite, and iron oxide, which present low levels of liberation, being mostly completely liberated below 100 µm but maintaining strong associations with calcite. Light-colored impurities also cluster with biotite, tend to form binary and ternary particles, while dark minerals, such as iron oxide and titanite, are predominantly found in binary associations with calcite. Minerals such as orthoclase and quartz, which have similar densities to calcite, challenge its separation, unlike iron oxide and titanite, which are more easily separated due to their different densities. Furthermore, particle shape analysis suggests that characteristics such as moderate circularity, slight elongation, and slight angularity would promote rapid sedimentation, enhance particle mobility, and stability in a gravity separation equipment. Finally, the concentration criterion reveals that only iron oxide would meet the criteria for gravity separation, however the MLA results indicate that it would not meet a suitable size for separation; suggesting that no impurities could be separated by a traditional gravity separation method, requiring a new method to achieve mineralogical and color purification of the material.