Chile is recognized as the producer of 28.5% of the world’s copper, around 5.7 million metric tons, and 22% of lithium, around 18 thousand metric tons. However, Chilean mineral deposits offer much more, and efforts have begun to focus on other metals and minerals in the primary and secondary resources. Chile’s long mining history includes copper, iron, gold, and molybdenum, mainly. This has meant that, according to the August 2020 update of the Tailings Deposits Registry of Sernageomin (Chilean National Geology and Mining Service), currently Chile hosts a total of 757 tailings deposits, of which 112 are active, 467 are inactive, 173 are abandoned, and 5 are under construction. Both industry and society are aware of the potential risks that tailings deposits can present, and that they require ongoing management. Nonetheless, they are also potential resources for helping supplement the demand for critical metals. Currently, the challenge in Chile is to acquire knowledge and apply it to critical metals recovery through a sustainable mining point of view.
What are critical metals?
It is generally agreed that critical metals are a formally defined term for metals that are economically important but have a high potential for supply disruption, often because one or two mines, or one country dominates the supply. Each geographical region considers different raw materials to be critical. For this reason, there are different lists of critical metals from the European Union, the United States and Australia. Some of the critical metals that have been declared by these countries include cobalt (Co), vanadium (V), gallium (Ga), germanium (Ge), and Rare Earth Elements (REE). Likewise, the list of critical metals changes with time as new manufacturing processes or new mines change the demand and supply situation.
Critical metals are essential components in the manufacturing of green technology, such as electromobility, wind turbines and solar panels, which are needed for the global transition to low-carbon emissions. The clean energy transition and growing availability of high-tech devices establishes a mineral intensive demand for critical metals, which provides enormous opportunities for mining operations (both small- and large-scale) from primary to secondary resources. Consequently, critical metals play a crucial role in ensuring compliance with the United Nations’ Sustainable Development Goals (SDGs), moving from “affordable and clean energy” to “responsible consumption and production”. According to “Risks and Opportunities of the Mining Industry” by EY in 2021, the radar -Decarbonization and green agenda- has been declared fourth as of 2020, which reflects the high challenge of industrial mining to turn to green energies and the introduction of greenhouse gas regulations in their operations. Undoubtedly, this new challenge must be tackled from a responsible perspective, continuing the strong commitment to environmental, social and governance sustainability. That being said, although critical metals have a huge demand worldwide, they remain greatly understudied from a geometallurgical point of view.
A vital step is understanding the controls on the distribution of critical metals, in terms of the tenor and deportment of them into ore and gangue minerals within different mineralization systems and, therefore, whether these critical metals can be processed and extracted at a profit. The use of advanced microanalytical techniques such as EPMA, LA-ICP-MS (Photo 1) among others and supported with advanced mineralogical techniques (a bulk mineralogy point of view) is imperative. If these are applied to secondary resources (e.g., tailings, waste rock, slag) characterization, it is a key step towards a revalorization of mine waste as a circular economy principle, an important approach to economic growth that is aligned with sustainable development.
Element distribution maps in pyrite, generated with LA-ICP-MS. Photo by Javier Quevedo, 2020.
In the mining industry, the circular economy is primarily related to the potential that exists in the reprocessing of tailings. However, recovery of other elements and minerals (beyond critical metals) may require consideration of a holistic innovative approach. This could provide secondary products for mining companies, which may choose to boost local markets by providing a regional entrepreneur with the opportunity to receive and manage material based on the exploitation of tailings, being a viable option for the development of economic, organizational, technological, environmental and social of the community.
Joaquín González, a student of geology at Universidad de Chile, did his internship program at SMI-ICE-Chile, specifically with the Geology Research Area (Photo 2) focused on critical metals in several minerals hosted in Chilean ore deposits. Through a literature review, Joaquín created a database (n= 585 data values) where the critical metals evaluated were Co, Ni, Ga, Te, Ti, V -across different microanalytical techniques- in pyrite, chalcopyrite, bornite, chalcocite and magnetite hosted in IOA, IOCG, porphyry copper, epithermal and stratabound deposits.
Pyrite is the mineral that shows a highly enriched concentration of cobalt. For instance, (Co)-rich pyrites hosted in IOA deposit up to 40,000 ppm of Co, in IOCG deposit up to 25,000 ppm, in porphyry copper deposit up to 24,050 ppm, in epithermal deposit up to 3,000 ppm, and in stratabound deposit up to 400 ppm. Therefore, as a mining country, Chile has the opportunity to deeper evaluate the recovery of critical metals as by-products with promising returns.
Geology researchers at SMI-ICE-Chile and geology intern from Universidad de Chile
A Collaborative Team
The Geology and Mineral Processing’s Research Area at SMI-ICE-Chile has gained valuable experience about critical metals in recent years through studies applied to cobalt hosted in IOCG primary deposits through projects with major mining companies, research thesis and internships, as well as research carried out in-house. These projects have included exploratory analysis data (EDA) through sample results that have been subjected to geochemistry analysis, mineralogical assessments (XRD, SEM, MLA-SEM), mineral chemistry assessments (LA-ICPMS), and metallurgical testing (grinding and flotation tests). Due to the demand, critical metals are set to expand worldwide over the coming decades, it is important to encourage the understanding, knowledge, and applicability of critical metals recovery from primary and secondary Chilean deposits, bringing new opportunities for commodities beyond copper. SMI-ICE-Chile with the collaborative support of SMI-UQ are evaluating projects focused on the potential for critical metals extraction as a by-product from existing and new mines.
 Iron oxide ± apatite (IOA), and iron oxide-copper-gold (IOCG) type mineral deposits.
Quevedo, Javier (2020) “Concentración y distribución de cobalto en piritas del depósito IOCG La Estrella, Región de Atacama, Chile”. Degree thesis, Universidad Mayor, Santiago, Chile http://repositorio.umayor.cl/xmlui/handle/sibum/6875
Mejías, Olivia (2020) “Geochemical assessment of critical metals: A geometallurgical guideline for the evaluation of by-products of an IOCG type deposit, Chile”. Procemin-Geomet conference proceedings, Santiago, Chile http://www.gecaminpublications.com/procemin-geomet2020/