Development of a methodology to characterize samples containing gold and tellurium to better identify and assess the deportment of these elements between bearing phases :a case study (Macassa processing plant) (ULiège)

Abstract

The investigation of mineral components is a vital factor in the study of orebodies within mining industry. In gold industry the mineral characterisation of the ore is important to evaluate possible challenges in extraction but also possible byproducts opportunities. This thesis evaluates the effectiveness of the methodology for gold and tellurium deportment of primary resources testing it on the Macassa gold and tellurium bearing ore. The Macassa operation is an ideal case study due to its high grades of gold and tellurium present in the form of tellurides. The study was conducted applying several techniques based on a literature review on gold deportment methodology. Hence, it included a comprehensive assay for multiple elements, sample pre-concentration, SEM mineralogical analysis and diagnostic leaching test. Three different pre-concentration methods were employed and compared. The significance of the procedure proposed by the authors Zhou and Cabri (2004) was proved, nonetheless some limitations were highlighted. Specifically the gold and tellurium quantitative mineralogical balance manifested notable challenges. These minerals have been characterised in different plant streams and therefore the fraction of gold and tellurium carried by each mineral was computed. In the run of mine, gold was detected with a grade of 14.25 ppm distributed among the mineral phases native gold (accounting for approximately 50% of gold) and calaverite (accounting for the almost all remaining percentage) with just a smaller amount (2%) in petzite. Moreover, the analysis suggests that in the leach feed stream the gold deportment is consistently shifted toward the calaverite with only a small amount (that was computed to be 5%) present as native gold. At the grinding target size (P80 = 20 μm) it is possible to say that at least up to 96.55 % of gold is not locked, hence potentially recoverable by cyanidation. Tellurium was detected in the run of mine at 21 ppm distributed in the mineral altaite and calaverite with only a small amount in the mineral petzite. At Macassa, tellurium is lost to the tailings but the tailings assessment emerged to be particularly challenging. However, some encouraging findings suggest that further study might demonstrate the feasibility of producing tellurium as a byproduct. Eventually the results have been commented regarding their representativeness and accuracy with the aim to improve the systematics for the study of gold and tellurium by not only identifying the element’ forms but also quantifying them.