The critical importance of mine waste- an Australian Perspective

Australia, whilst host to many greenfield exploration and new mining activities, also contains at least 50,000 abandoned or historic mine sites. These may not necessarily present immediate or long-term environmental risks (e.g., noxious dust or acid and metalliferous drainage (AMD) formation), but may still contain mine waste (e.g., tailings, waste rock, slag) ultimately requiring rehabilitation. Who is ultimately required to fund and complete rehabilitation may be controversial and/or contentious depending on the circumstances of mine closure. However, across Australia, there is a growing recognition that these sites may contain critical raw materials (CRMs), particularly those required for the energy transition leading to the birth of several research programs to investigate the secondary prospectivity of mine waste. In addition to individual mining companies, Geoscience Australia and the Queensland, New South Wales, Northern Territory and South Australian Governments have commissioned research to investigate the tenor and deportment of critical metals (as identified by the Australian Government) including cobalt, rare earth elements (REE), vanadium, indium, gallium, germanium, selenium, antimony, bismuth and manganese. Currently, over 40 sites have been sampled (targeting tailings, waste rock and metallurgical wastes including slag, phosphogypsum slimes, spent heap leach and coal combustion products) and assessed using an integrated geometallurgical testing program.

Early results have identified REEs (lanthanum and cerium) in tailings and waste rock at the Mary Kathleen mine, Queensland. New metallurgical extraction methods are being developed to enable ‘greener’ recovery. In addition, cobalt has been identified in the waste associated with iron-oxide copper gold (IOCG) and sedimentary hosted copper deposits in the North West Minerals Province, Queensland encouraging operational mines to consider mineral processing plant modifications to recovery this battery metal. Distinct manganese enrichment has been observed in wastes associated with Broken Hill type deposits, whilst indium is associated with volcanic hosted-massive sulphide (VHMS) and greisen deposits. Ongoing research is focused on developing business cases for CRM extraction at fertile sites. Post extraction, additional valorisation opportunities are being sought (e.g., aggregates, sulphuric acid production, ore sands) for the residual waste, and those barren (in CRM terms). By considering mine waste in these terms, Australia has an opportunity to significantly establish and grow their circular economy and take steps towards meeting their ambitious economic targets (AUD $26 Billion by 2025).