By-product Metals Research Articles

The world's by-product and critical metal resources part II: A method for quantifying the resources of rarely reported metals

Estimates of the world's mineral resources of numerous by-product metals remain highly uncertain at best, despite the high criticality of many of these elements to society. This stems from the limited reporting of the concentrations of these elements within mineral deposits by the mining industry, meaning that we require methods to estimate the availability of these resources that overcome this limitation. Here, we present a method for quantifying poorly reported mineral resources of by-product metals that builds upon deposit-by-deposit approaches to global resource estimation, arguably the best-practice approach for well-reported commodities, but also adds the use of proxies for by-product grade estimation. This proxy method allows for deposits with known or inferred by-product metals to also be incorporated within global resource estimates and provides a greater basis for assessing future supply potential.We demonstrate the application and verification of this methodology with indium, a critical metal for which <1% of identified zinc, tin, and copper deposits potentially hosting indium mineralisation report grades using CRIRSCO (or equivalent) mineral resource reporting codes. The use of the method outlined in this manuscript will allow the global resources of any metal commodity, especially the often under-reported by- and co-product metals that are becoming increasingly essential to modern life, to be quantified to a significantly greater level of accuracy and precision than is allowed by other approaches.

Byproduct Metal Availability Constrained by Dynamics of Carrier Metal Cycle: The Gallium-Aluminum Example.

Future availability of byproduct metals is not limited by geological stocks, but by the rate of primary production of their carrier metals, which in turn depends on the development of their in-use stocks, the product lifetimes, and the recycling rates. This linkage, while recognized conceptually in past studies, has not been adequately taken into account in resource availability estimates. Here, we determine the global supply potential for gallium up to 2050 based on scenarios for the global aluminum cycle, and compare it with scenarios for gallium demand derived from a dynamic model of the gallium cycle. We found that the gallium supply potential is heavily influenced by the development of the in-use stocks and recycling rates of aluminum. With current applications, a shortage of gallium is unlikely by 2050. However, the gallium industry may need to introduce ambitious recycling- and material efficiency strategies to meet its demand. If in-use stocks of aluminum saturate or decline, a shift to other gallium sources such as zinc or coal fly ash may be required.

The world's by-product and critical metal resources part I: Uncertainties, current reporting practices, implications and grounds for optimism

Many of the metals extracted as by-products and rated as ‘critical’ are vital to important modern technologies but are seldom reported as extractable commodities by the mining industry. This creates numerous uncertainties and challenges in estimating the global resources of these metals; here we outline the current approaches (or lack thereof) used in resource reporting and identify and discuss the uncertainties surrounding critical co- and by-product reporting in detail. We present a review of ore reserve and mineral resource reporting in the mining industry, including the identification of various methods by which resource accounts have been constructed, a discussion of examples and differences between countries, states and organisations that conduct these assessments, and a discussion of the various ways in which these resource data have been interpreted. This is followed by a series of case studies that document and discuss the reporting of selected critical metals that suggest that the lack of reporting is dominantly as a result of the perceived or actual low monetary value of by-products at the mine site rather than as a result of any lack of these metals, indicating that different types of uncertainties can arise in estimating the global resources of these critical commodities.This paper also addresses (and continues in parts II and III) the numerous issues and uncertainties identified in this study by outlining approaches and alternative data sources that can be used to develop more comprehensive assessments of critical metal resources from deposit to global levels. The hybrid methodologies proposed in this paper provide reasons for some optimism in that by-product and critical metal resources can still be identified to a reasonable degree of accuracy, and these resources are likely to be sufficient to meet demand for some decades. However, there is still a strong case for improved reporting of by-products and critical metals in mineral deposits to assist in these efforts and to clarify the true global position in terms of the future security of supply of co- and by-product metals, invariably including the critical or e-tech metals.

Volatility of by-product metal and mineral prices

Prices of by-product metals and minerals are often assumed to be inherently more volatile than prices of main and individual products. Yet there is limited analysis of their relative price volatilities. This paper applies regression analysis to compare the price volatility of by-product metals and minerals to commodities produced primarily or solely as main-products or individual products. This approach allows for estimating whether by-product supply is associated with greater price volatility and provides a framework for further research. By-products are found to have on average about 50% higher price volatility than main and individual products when evaluating annual prices over the last 50 years – although there are exceptions. However, when analyzing monthly prices over the past decade, the evidence that by-products have greater price volatility is mixed.

By-product metals are technologically essential but have problematic supply.

The growth in technological innovation that has occurred over the past decades has, in part, been possible because an increasing number of metals of the periodic table are used to perform specialized functions. However, there have been increasing concerns regarding the reliability of supply of some of these metals. A main contributor to these concerns is the fact that many of these metals are recovered only as by-products from a limited number of geopolitically concentrated ore deposits, rendering their supplies unable to respond to rapid changes in demand. Companionality is the degree to which a metal is obtained largely or entirely as a by-product of one or more host metals from geologic ores. The dependence of companion metal availability on the production of the host metals introduces a new facet of supply risk to modern technology. We evaluated companionality for 62 different metals and metalloids, and show that 61% (38 of 62) have companionality greater than 50%. Eighteen of the 38-including such technologically essential elements as germanium, terbium, and dysprosium-are further characterized as having geopolitically concentrated production and extremely low rates of end-of-life recycling. It is this subset of companion metals-vital in current technologies such as electronics, solar energy, medical imaging, energy-efficient lighting, and other state-of-the-art products-that may be at the greatest risk of supply constraints in the coming decades.

Towards the Recovery of By-Product Metals from Mine Wastes: An X-Ray Absorption Spectroscopy Study on the Binding State of Rhenium in Debris from a Centennial Iberian Pyrite Belt Mine

Rhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on ex- ploring residues resulting from a long-term mining, particularly of sulphide ore deposits. It is therefore noteworthy to assign the presence of rhenium (in a concentration up to 3 ppm) in the waste materials from the old sulphur factory at the abandoned mine of Sao Domingos (Iberian Pyrite Belt, Southeast Portugal), exploited since the Roman occupation of Iberia. Aiming at a potential sustainable recovery of rhenium as a by-product, X-ray near-edge absorption spectroscopy (XANES) was applied to clarify the Re-binding and mode of occurrence by comparing Re L3-edge XANES spectra obtained from mine waste samples (previously fully characterized by X-ray laboratory techniques) with similar spectra collected from Re-rich molybdenites (Mo1-xRexS2) and from Re-O model compounds configuring various valences and coordination environments of rhenium ions. Obtained results are commented, ruling out a possible Re-S binding and rather conforming with the binding of rhenium to oxygen in the analysed mine waste materials.

On the geological availability of germanium

Based on a detailed statistical analysis of chemical data published in the scientific literature, estimates were made of the minimum amounts of recoverable Ge contained within sulphidic zinc ores and coals, given current processing technologies. It is expected that at least 119 kt (∼7 kt in zinc ores and ∼112 kt in coal) of recoverable germanium exist within proven reserves (at present stage of knowledge) at grades in excess of 100 ppm in sphalerite and 200 ppm in coal, while at least 440 kt (∼50 kt in zinc ores and ∼390 kt in coal) should become recoverable in the future, being associated to coal reserves at 8–200 ppm Ge and zinc resources containing in excess of 100 ppm Ge in sphalerite. Mississippi Valley Type (MVT) deposits are expected to be the most important hosts of germanium-rich sphalerite, while both brown and hard coals are expected to be equally important as hosts of germanium. The approach taken in this publication shows that reliable minimum estimates for the availability of by-product metals lacking suitable reserve/resource data may be attained by using robust statistical methods and geochemical data published in the scientific literature

Quantifying the recoverable resources of by-product metals: The case of cobalt

The long-term availability of mineral resources is crucial in underpinning human society, technology and economic activity, and managing anthropogenic environmental impacts. This availability is increasingly true for metals that do not generally form the primary product of mines, such as copper or iron, but instead are recovered as by-products (or sometimes co-products) during the processing of primary ores—also known as ‘companion metals’ (e.g., indium, cobalt, molybdenum, rhenium, selenium). These metals, however, can be of significant economic and technological importance, both to a mine's economics and in downstream applications. It is therefore useful to develop methodologies to estimate the “recoverable resource” for such companion metals, i.e., the amount that could, if desired, be extracted and put into use over the next several decades. Monitoring the supply and demand of these resources is important to enable the identification of any changes that may have significant repercussions for the global economy, technology needs, and the environment. Here, we derive an estimate of the recoverable resource for cobalt (Co), a metal used with increasing frequency and in larger amounts in modern technology that is mainly recovered as a by-product of copper and nickel ore processing and production; Co-only mines are few in number and typically small in size. Our methodology combines the reported size of ore bodies that host Co with measured or estimated Co concentrations in the ores within these bodies. The dominantly by-product nature of Co means that uncertainties exist for some of the Co grades as well as recovery rates; given this, we also split our total recoverable Co resource, using a resource estimate data quality classification, into high, medium and low quality data, depending on factors such as whether statutory resource reporting codes were used during resource reporting. This methodology indicates that a minimum of 26.8Mt Co is present in current global Co resources, with 15.2, 5.6 and 6.0Mt Co in high, medium and low quality resources, respectively. Applying typical recovery rates for different ore types indicates that ~15.9Mt of this Co is recoverable, with ~10.7, ~2.6 and ~2.6Mt Co recoverable in high, medium and low quality resources, respectively. This approach provides a basis for determining similar recoverable resource estimates of other companion metals, such as indium, rhenium, selenium, etc., all of which are of increasing importance in modern day life.

On the Future Availability of the Energy Metals

The routine availability of metals, long assumed by materials scientists to be unworthy of concern, is now a topic of wide interest but one with little clear guidance. This review discusses availability issues from the perspective of the metals utilized in the energy industry. Although the availability of metals is a dynamic characteristic, availability of the widely used base metals appears assured in the immediate future. The same cannot be said for by-product (daughter) metals, which are increasingly vital for many carbon-free energy technologies but are produced only if recovered as part of parent metal processing. Additionally, the direct substitution of one metal for another in short supply is often difficult because the best substitutes tend to have the same availability constraints as did the original metal. Gallium, indium, and neodymium are singled out as elements of particular concern from a long-term-supply standpoint.

Continuous oxygen steelmaking with copper-, tin-, and zinc-contaminated scrap

In the context of a new zero-gas-emission process for continuous oxygen steelmaking, desorption of copper, tin, and zinc from liquid scrap are modeled. Additive diffusional-resistance concepts show that zinc elimination at atmospheric pressure is entirely straightforward. For copper and tin, a reduced pressure (2.5 mbar) and a relatively high temperature (1780 °C) are preferred. Sulfur must be added above the stoichiometric requirements to volatilize tin sulfide. Copper elimination by physical desorption is completely predictable, but with tin, interfacial chemical kinetics may possibly exert an influence. Based on exclusive transport control and the currently available pumping capacity for vacuum degassing steel, the engineering feasibility of refining continuously melted steel scrap is established. Dimensions are estimated for producing 2 Mtpa of steel with a scrap-to-virgin iron ratio of 3 to 1. Electrical conductive heating is required to raise the liquid-scrap temperature toward the limits imposed by current refractories. With the proposed new technology, copper, tin, and zinc are all recovered as by-product metals. Pretreatment of steel scrap is not advocated, other than simple physical segregation at the source.

The Recovery of Values from Non-Ferrous Smelter Slags

AbstractIn a number of cases some form of slag treatment is necessary to recover values that would otherwise be lost.The replacement of traditional smelting processes with new, more energy efficient and environmentally acceptable processes, combined with the need to maximize recoveries, has increased the need for slag treatment. The reasons for this are discussed and various slag treatment processes are compared on the basis of costs, energy consumption, and recovery efficiencies.Several approaches are available on a commercial basis, and the selection of anyone approach will depend on a number of factors. Current methods for cleaning slags from copper, nickel and lead smelters prior to disposal are reviewed. The recovery of both primary and byproduct metals is discussed. In addition, the removal and/or recycle of undesirable impurities is assessed from the point of view of impurity distribution and the effect on other operations within the smelter.Proven slag cleaning processes are described and simplifi...