Defining the acid forming potential during the exploration stages of a mining project is critical for financial modelling and waste management planning. However, at such early stages, there are limited resources for evaluating the geoenvironmental characteristics of future waste materials. Considering this, several new methodologies were developed in 2018. First, continuing to add value to the hyperspectral data collected in the project undertaken with Boliden at the Lil-Laverberget porphyry, Sweden, we developed the new Hy-Gi which enables Hylogger data to be used for the domaining of geoenvironmental risk. These results were published in the Geometallurgy special issue of Minerals. In this special issue we also published the results of a cross-theme collaboration with Matthew Cracknell, whereby we sought to automate the acid rock drainage index. Machine learning algorithms were developed and tested on materials being used in the PhD study currently being undertaken by Laura Jackson.

The international collaboration with the Australian Academy of Technology and Engineering continued with waste materials from three different sites in Africa, Europe and Australia tested. New biokinetic tests and sized automated mineralogy experiments were performed in addition to accelerated static tests at UTAS. The preliminary results were presented at Process Mineralogy 2018 and all data will be evaluated in early 2019 and final recommendation presented to the ASTM Committee by Q2 2019.

Defining the acid forming potential during the exploration stages of a mining project is critical for financial modelling and waste management planning. However, at such early stages, there are limited resources for evaluating the geoenvironmental characteristics of future waste materials. Considering this, a new geoenvironmental logging code was developed and trialled using drill cores from the low-grade Lill-Laverberget (Laver) porphyry copper prospect in Northern Sweden. Four drill holes were targeted with a focus on zones which were marginal or below economic grade. The logging code developed required that for each metre interval, a visual estimate of each sulfide present was recorded. As a conservative approach was adopted, the area (8.5 cm by 5.5 cm, i.e., grain size card dimensions) recognised to contain the most sulfides, was assessed using the acid rock drainage index. A geoenvironmental risk factor was calculated based on acid rock drainage index values scaled to the sulfide mineral abundance over the interval. To enhance the classification, results were screened against sulfur assay values. As corresponding drill core pulps (< 75 μm) were available in this study, they were analysed using the ASTMD492-01(2007) paste pH method.

Collectively, these cost-effective, low-technology methods enabled the identification of high- and low-risk waste zones and will allow the mine planners to start developing robust waste management strategies rightly guided by the deposit’s mineralogy and texture with these results presented at the 9th AMD Workshop, Burnie, Tasmania, in November 2017. In addition, the microtextural controls on oxidation were examined per waste lithology sampled, and free draining column leach kinetic cells for several of these waste lithologies established in mid-2017. Collectively, these results will help the company understand the geoenvironmental characteristics of their waste materials therefore helping them to develop a waste management plan.

This project is looking at aspects of waste classification to better understand and manage current and planned sites.

During the year, Grange Resources proposed a study focused on determining the accuracy of the net acid generation (NAG) pH test. This test is used widely by the mining industry for rapid waste classification, and involves several stages, including length of reaction time, heating temperature, and cooling time before pH measurement. The study scrutinised each stage to determine the effect on the overall test results. Outcomes included the development of a site-specific NAG pH testing protocol (suitable for the waste types encountered at Grange Resources’ Savage River operations), with a journal article also in preparation.

Another element of this project was a review of the Terra portable XRD instrument, manufactured by Olympus. This instrument has the ability to rapidly measure the mineralogy of a dried sample, with full phase identification and quantification capabilities. Testing of the instrument was conducted on various drill core and mine waste materials, with the results summarised in an internal TMVC report.