2018 Chetty Acid gangue interactions in heap leaching

Heap leaching accounts for a fifth of global copper production, sourced primarily from porphyry ores, yet metal recoveries are often not optimal. Gangue, and its interaction with acid, plays an important role in such processes. Thus, a proper understanding of gangue minerals present in the ore, their textural relationships relative to particle size distribution, reactivity with acid under different conditions, and relationship to lithotypes and geological alteration in the orebody, is necessary to predict ore behaviour in the comminution, agglomeration, curing and heap leach unit operations. Various mineralogical tools, including routine X-ray diffraction and automated scanning electron microscopy, alongside advancements like hyperspectral infrared imaging, are employed for characterisation. Integrated techniques allow assessment of mineral abundance, textural relationships, and mineral chemistry over different particle sizes. Additionally, diagnostic leach results can be improved when correlated with robust mineralogical data. This study emphasizes the significance of ore attributes and metallurgical behaviour linked to gangue-acid reactivity and suggests further investigations into the effects of temperature and fluid dynamics during heap leaching. A refined understanding of gangue mineral reactivity could enhance the outcomes of comminution and leaching processes.