Reinventing the Wheel: the Environmental Geometallurgy Matrix and its Supporting Tools

The challenge remains for the mining industry to identify the mechanisms by which to cost effectively forecast and manage geoenvironmental risks at the earliest possible stage in a mine’s life. If adequately performed, appropriate allocation of funds and environmental management strategies can be developed and embedded into the mine plan enabling better closure outcomes. Whilst the metalliferous mining industry is cognisant of this, another major challenge is finding the right tools to facilitate early stage waste characterisation. For example, chemical (i.e., static and kinetic) tests have dominated how AMD properties have been measured since the late 1970s, but with AMD remaining an ongoing global issue (even at young mines), there is a necessity for innovation. With an explosion of new tools and technologies for ore characterisation, there has never been a more opportunistic time to follow an environmental geometallurgy matrix approach whereby the geoenvironmental toolbox is used for waste characterisation. The toolkit includes application of hyperspectral technologies to derive geoenvironmental domaining index and automated acid rock drainage index values, improved used of handheld tools and chemical tests, data mining, and finding new applications for µCT and 3D XRF drill core scanners. This paper focusses on demonstrating applications of hyperspectral datasets as the metalliferous mining industry trend is currently towards collecting these data during early life-of-mine stages. As we approach the next decade, the industry has the unique opportunity to adopt the environmental geometallurgy matrix and embed the use of the geoenvironmental toolbox into their operations to improve risk management

Geometallurgical characterization of non-ferrous historical slag in Western Tasmania: Identifying reprocessing options

Pyrometallurgical processing of ore from the Zeehan mineral field was performed intermittently between 1896 and 1948, primarily recovering Pb, Ag and Cu. While Zn recovery was attempted at the time, it was unsuccessful using the available technology. Consequently, Zn reported to the slag during the smelting process. Today, the former smelter site consists of two large slag piles (North and South). Using a range of techniques (including X-ray diffractometry, scanning electron microscopy, laser ablation inductively coupled plasma mass spectrometry, and static testing) the geometallurgical and geo-environmental properties of these slag materials (n = 280) were determined. The South and North piles contain on average 15% and 11% Zn, respectively. A range of complex mineral phases were identified, and are dominated by glass, silicates (i.e., monticellite-kirschsteinite and hardystonite), oxides (gahnite and hercynite) and minor sulfides (sphalerite and wurtzite). Microtextural examinations defined nine mineral phases (Glass A, Silicates A to D, Oxides A and B, Sulfides A and B). Zn was concentrated in Sulfide A (26%), Glass A (24%) and the Silicates (43%), while Pb was concentrated in Oxide B (76%), with Sulfide B host to the highest Ag (45%) and Cu (65%). Considering this, recovery of Zn using conventional hydrometallurgical processes (i.e., sulfuric acid leaching) is suitable, however the application of unconventional biohydrometallurgical techniques could be explored, as well re-smelting. These slag materials are classified geo-environmentally as potentially acid forming, with leachate concentrations of Zn, Pb consistently above ANZECC (2000) aquatic ecosystem 80% protection guideline values, and, for the majority of samples, exceedances of Cu, Ni and Cd were also measured. Considering these findings, reprocessing of these historic slags for Zn extraction may provide an economically feasible management option for rehabilitating this historical site

Prediction of Acid Rock Drainage (ARD) from Calculated Mineralogy

ABSTRACT The acid-forming potential of ore and waste can be calculated based on a detailed knowledge of mineralogy, especially sulphide and carbonate contents. However, most mineralogical techniques (e.g., semi-quantitative X-ray diffraction (qXRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) point counting) are too expensive for routine application. Mineralogy can be calculated from assay data using linear programming (simplex method) which is a mature method with application to real world quantities that cannot be negative. In order to apply this method, a table of mineral compositions is required for all the significant minerals in the study area. Unlike least squares methods, the mineral list can exceed the number of elements included in the assay data. Several carbonate compositions with a range of neutralising potential can be included. To use the linear programming method, a calibration must be established based on known compositions. This calibration can be based on qXRD or SEM/EDS point counting methods. Not all types of assay data are sufficient for calculating mineralogy reliably. The best assay data comes from X-ray fluorescence analysis of major elements, including "loss on ignition" (LOI). Adding measured C content to this analysis provides a robust data set for calculating sulphide and carbonate contents of rocks. The mineralogy can be calculated without measured C, if LOI and SiO2 are included in the analysis. However, typical mine databases contain multi-element assays based on a four-acid digestion method. In this case SiO2 is not analysed and there is no "LOI" or total C. With typical four acid digestion data it is not possible to estimate the original carbonate content even when the mineralogy is simple. In rocks with complex mineralogy, mixed carbonates and/or multiple sulphides, qXRD and full chemical analyses are required to calculated acid rock drainage potential from mineralogy

Evolution of sulfidic legacy mine tailings: A review of the Wheal Maid site, UK

This is the final version. Available from MDPI via the DOI in this record.Data Availability Statement: Original data contained within the article and supplementary material are openly available in Mendeley Data at http://dx.doi.org/10.17632/hrw4vksyyk.1 (accessed on 20 June 2021).Historic tailings dams and their associated mine waste can pose a significant risk to human and environmental health. The Wheal Maid mine site, Cornwall, UK, serves as an example of the temporal evolution of a tailings storage facility after mining has ceased and the acid‐generating waste subjected to surficial processes. This paper discusses its designation as a contaminated land site and reviews our current understanding of the geochemistry, mineralogy, and microbiology of the Wheal Maid tailings, from both peer‐reviewed journal articles and unpublished literature. We also present new data on waste characterisation and detailed mineral chemistry and data from laboratory oxidation experiments. Particularly of interest at Wheal Maid is the presence of pyrite-bearing “Grey Tailings”, which, under typical environmental conditions at the Earth’s surface, would be expected to have undergone oxidation and subsequently formed acidic and metalliferous mine drainage (AMD). The results identified a number of mechanisms that could explain the lack of pyrite oxidation in the Grey Tailings, including a lack of nutrients inhibiting microbial Fe(II) ox-idation, passivation of pyrite mineral surfaces with tailings processing chemicals, and an abundance of euhedral pyrite grains. Such research areas need further scrutiny in order to inform the design of future tailings facilities and associated AMD management protocols.Natural Environment Research CouncilNatural Environment Research CouncilNatural Environment Research Counci

Cobalt and other critical metals in tailings of major mineral deposits in north Queensland: Progress update- Interim Report 2 for the Department of Natural Resources, Mines and Energy

The mine waste features at 9 sites in Queensland (Lady Annie, Capricorn Copper, Century, Osborne, Selwyn, Baal Gammon, Wolfram Camp, Mt Oxide, Pindora) have been sampled for new economy metal exploration funded by the GSQ. Preliminary assay data for these samples has been collected (NB. some samples require additional analysis) so only limited interpretations are presented in this interim report. Samples were collected from 6 sites in January-February 2020, with tailings samples also provided from the New Century, Osborne and Chinova sample stores)

Reinventing the wheel

New approaches to predicting the outflow of acidic water from mines are needed to reduce the significant management costs of this environmental hazard. The geochemistry-mineralogy-texture (GMT) approach is one of such kind, which comprises of three stages. Stage one is a mandatory pre-screening stage, which focuses on using small scale, inexpensive geochemical and mineralogy tests as well as textural evaluations. At stage two, the acid forming, or neutralizing potential is quantified using standard geochemical tests. At stage three, the controls on sulphide oxidation are realized using advanced analytical techniques. Through understanding the controls, detailed acid rock drainage (ARD) predictive models can be developed and their long-term geochemical behavior understood