A GEOMETALLURGICAL PERSPECTIVE ON RESOURCE ESTIMATION AT LEGACY MINE SITES

Traditional approaches used to define mineral resources are not directly translatable to legacy mine sites. For example, elemental enrichment relative to crustal abundance provides valuable insight when defining a mineral deposit, but at legacy sites extra caution is necessary because unlike a new mine, the material has already been processed. This processing provides several benefits such as reduced comminution requirements, substantial knowledge from the outset, and the opportunity to perform waste remediation. However, elements previously unrecovered are going to be more difficult to recover than would be expected given equivalent assays at a greenfield operation.

Additional factors must be considered in assessments of the critical mineral potential of legacy sites. Critical elements produced as byproducts, such as In, Te, and V, are not major economic motivators for operations. In these instances, recovery is only economical feasible due to production of the primary commodity. Further, most byproduct recovery is only possible due to concentration during the downstream metallurgical processes applied to the primary commodity. Assaying alone does not address the interdisciplinary relationship between mineralogy and metallurgical processing. Assay based estimates can grossly overestimate the producible critical elements contained at legacy mine sites by including the fraction that would not be enriched into downstream processes.

This presentation examines tellurium production and other examples to highlight and address the challenges in resource estimations for legacy sites. The presentation explores the substantial role historical processing methods have on the recoverability of contained elements, in addition to the potential routes for recovery based on technologies available today and under development.