Characterising chalcopyrite liberation and flotation potential: Examples from an IOCG deposit Julie Hunt a,⇑ , Ron Berry b , Dee Bradshaw b a CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Private Bag 79, Hobart, Tasmania 7001, Australia b Julius Kruttschnitt Mineral Research Centre, University of Queensland, Australia article info Article history: Available online 10 May 2011 Keywords: Classification Liberation analysis Mineral processing Simulation Modelling abstract A critical aspect of geometallurgy is quantifying mineralogical and textural relationships that affect min- eral processing (e.g., liberation and recovery) and it is vital that this information is included in the plan- ning process for both mining and mineral processing. However, to date, this has been an expensive and time consuming venture and only minimal amounts of this type of data are available to be included in the planning process. Our research is focused on developing new methods that will produce the required mineralogical and textural data rapidly and inexpensively. These include obtaining quantified textural data, such as the size and distribution of the valuable phase and its association with other minerals, by extracting it directly from mineral maps. In addition, simulated breakage of drill core samples was used as a rapid way of looking at various particle sizes to determine potential liberation behaviour. The predicted liberation parameter compares favourably with results obtained from typical MLA recovery analysis, is spatially coherent and can be used to recognise domains of high and low liberation potential that are expected to affect the grade recovery curve. The flotation response was evaluated and the tech- nique validated using a small scale test being developed at the Julius Kruttschnitt Mineral Research Cen- tre, i.e. the JKMSI (mineral separability indicator). Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Practical geometallurgy requires a database of parameters that predict mineral processing performance. Obtaining this type of information rapidly and inexpensively is vital so that a represen- tative number of measurements can be carried out and the results included in the planning process for both mining and mineral processing. Recent advances in digital photography, particularly in image processing software, have led to a resurgence of interest in optical microscopy mineralogy as a source of rock texture information. Our work suggests that optical techniques have a place in generating medium quality cost-effective microscale mineral maps with direct application to geometallurgy. In the examples presented here we have used mineral maps produced through optical mineralogy and automated mineral identification plus simulated breakage as a rapid way of looking at various particle sizes to determine potential liberation (and flotation) behaviour. This method does not mimic actual breakage but can provide a way of ranking samples in terms of their relative processing behaviour. 2. Methodology 2.1. Image collection Ninety-six 2 m-long samples of half drill core containing copper mineralisation (as chalcopyrite) were chosen from five drill holes to give a cross-section through an iron oxide–copper–gold ore body. Each sample was crushed and a representative (riffle splitter) sample of particles in the size range from 1.18 to +0.6 mm was selected. As this particle size is more than five times the grain size of the Cu minerals it allows the fundamental rock properties to be measured before modification by grinding. The grain mounts typi- cally contain 500 particles and 1000–5000 grains of Cu sulphide. The coarse particles were mounted on a polished thin section and analysed using optical microscope techniques as described in Berry (2008), Berry and McMahon (2008) and Hunt et al. (2010). Image collection for each sample was carried out using a micro- scope with a high precision stage (<1 lm error in reproducibility) to allow the direct tiling of frames and good registration of multi- ple image layers. Transmitted-light plane-polarised, transmitted- light cross-polarised and reflected-light plane-polarised images were collected along with a transmitted-light cross-polarised im- age with a tint plate inserted. All lighting conditions were kept constant for all image acquisition. Exposures were set to avoid any saturated pixels. The images were collected at one third 0892-6875/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2011.04.016 ⇑ Corresponding author. Tel.: +61 3 6226 2782; fax: +61 3 6226 7662. E-mail address: Julie.hunt@utas.edu.au (J. Hunt). Minerals Engineering 24 (2011) 1271–1276 Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng