Rock-to-Metal Ratio: A Foundational Metric for Understanding Mine Wastes

Abstract

The quantity of ore mined and waste rock (i.e., overburden or barren rock) removed to produce a refined unit of a mineral commodity, its rock-to-metal ratio (RMR), is an important metric for understanding mine wastes and environmental burdens. In this analysis, we provide a comprehensive examination of RMRs for 25 commodities for 2018. The results indicate significant variability across commodities. Precious metals like gold have RMRs in the range of 10 5 –10 6 , while iron ore and aluminum are on the order of 10 1 . The results also indicate significant variability across operations for a single commodity. The interquartile range of RMRs for individual cobalt operations, for example, varies from 465 to 2157, with a global RMR of 859. RMR variability is mainly driven by ore grades and revenue contribution. The total attributable ore mined and waste rock removed in the production of these 25 commodities sums to 37.6 billion metric tons, 83% of which is attributable to iron ore, copper, and gold. RMRs provide an additional dimension for evaluating the impact of materials and material choice trade-offs. The results can enhance life cycle inventories and be extended to evaluate areas of surface disturbances, mine tailings, energy requirements, and associated greenhouse gas emissions.

Mass-Balance-Consistent Geological Stock Accounting: A New Approach toward Sustainable Management of Mineral Resources

“…This results in misunderstandings regarding what reported production data refer to (e.g., the total mass with average ore grade, or the total pure metal content of sold products) and allows for “hidden” inconsistencies. Moreover, published industry data generally only cover some selected materials and flows (e.g., omit to report removed waste rock), exclude relevant details (e.g., whole-rock composition including companion or critical metals and deleterious elements; mineralogy; pH; physical product qualities), , and may be preaggregated across projects to company-levels (i.e., not granular, site-scale). Moreover, depending on the jurisdiction, they may remain entirely undisclosed for entities that are not listed on stock exchanges, or that have revenues below a given threshold. , Similarly, government communication is a problem .…”

“…This scope partly explains why quantitative data on unused extraction are absent from national statistics. , Yet, this does not lessen their relevance for sustainability-related discussions. Hidden flows exert various pressures on the environment and can contain both potentially harmful and useful material . For open pit mines, hidden flows are commonly two, and occasionally 30 times bigger than the ore retained (used extraction), and orders of magnitude bigger than final sales quantities. , Globally, the mining industry is the largest “waste” producer, and in 2016 alone the flow of unreported waste rock was estimated to be 72 billion tonnes (Gt) . Altogether, the historical flow of nonsales quantities (hidden flows, reported tailings, and other residues) is estimated to have accumulated a total of several hundred Gt of mine wastes .…”

“…Still, data gaps on mine waste types, volumes, mineralogy, and composition continue to impede resource recovery from growing waste streams (“ mining ” of flows) and historical waste deposits ( remining of legacy stocks ). Similarly, Economy-Wide Material Flow Accounts and indicators for Material Footprints, Total Material Requirements, , Rock-to-Metal Ratios, and project-specific resource efficiency , are all hindered by the poor availability or lack of relevant, robust, and accessible site-scale material stock and flow data.…”

“…The mineral depletion and sustainability debate continues unabated, and while neither the optimistic nor the pessimistic perspective is inherently contradictory or incorrect, neither has offered a unifying solution to reconcile the positions. ,− Notably, both resource optimists and resource pessimists base their claims on the same national and global mineral production statistics and estimates for mineral resources and reserves. − Whether these data are at all suitable for quantifying long-term mineral depletion is questioned by recent studies. ,− Various authors highlight significant uncertainties regarding conceptual methods for estimation, classification, and spatial aggregation of mineral resources and reserves across all data sources, particularly for critical raw materials. − Moreover, the general lack of systematic and standardized granular mine-site-level “bottom-up” information is a key concern for comparing, aggregating, and monitoring mineral resources and mineral reserves. ,, Poor data availability also hampers environmental, social, and governance (ESG) risk assessments, , sustainability analysis, , and raw materials scenario modeling. ,, Notwithstanding, there are few recommendations on how mineral-related data collection may be streamlined and industry-government integration facilitated to address data gaps and fragmentation. Here, we use material flow analysis (MFA) and mass-balance (MB) principles to review current mineral reserve accounting, mine production monitoring, and industry-government data integration.…”

Underground hyperspectral outcrop scanning for automated mine‐face mapping: The lithium deposit of Zinnwald/Cínovec

“…Although hyperspectral imaging (HSI) has been proven to add value to exploration activities in surface mining environments, it has yet to be fully demonstrated in underground settings. The development of these techniques for underground mining is of high relevance for two main reasons: (1) compared with open‐pit mining, in which both low‐ and high‐grade zones of the ore body are typically mined, a more selective mining strategy is favoured in underground mining (Nassar et al, 2022; Nwaila et al, 2022), making the identification of ore versus gangue through geological face mapping critically important; and (2) currently, about 40% of worldwide mining operations are underground (Martino et al, 2021), a number expected to rise over the coming years due to the increasing depth of remaining mineral deposits and as part of the effort to reduce the environmental and societal footprint of mining (e.g., Sahu et al, 2015). However, underground mining operations are comparatively expensive and low volume, accounting for only 12% of global run‐of‐mine productions (Martino et al, 2021).…”