Physico-Chemical Characteristics of Spodumene Concentrate and Its Thermal Transformations

Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 microns and the degree of liberation of major minerals was found to be more than 90%. The thermal behavior of spodumene and the concentration of its polymorphs were studied by heat treatments in the range of 900 to 1050 °C. All three polymorphs of the mineral (α, γ and β) were identified. Full transformation of the α-phase was achieved at 975 °C and 1000 °C after 240 and 60 min treatments, respectively. SEM images of thermally treated concentrate revealed fracturing of spodumene grains, producing minor cracks initially which became more prominent with increasing temperature. Material disintegration, melting and agglomeration with gangue minerals were also observed at higher temperatures. The metastable γ-phase achieved a peak concentration of 23% after 120 min at 975 °C. We suggest 1050 °C to be the threshold temperature for the process where even a short residence time causes appreciable transformation, however, 1000 °C may be the ideal temperature for processing the concentrate due to the degree of material disintegration and α-phase transformation observed. The application of a first-order kinetic model yields kinetic parameters which fit the experimental data well. The resultant apparent activation energies of 655 and 731 kJ mol−1 obtained for α- and γ-decay, respectively, confirm the strong temperature dependence for the spodumene polymorph transformations.

Characterization of amalgamation tailings from ASGM in Sekotong area, West Nusa Tenggara, Indonesia, and its potential added value

Artisanal and small-scale gold mining (ASGM) in Indonesia still uses mercury in amalgamation process to extract gold form the ores. The process easily produces gold but at the same time produces very dangerous mercury waste. In this study, a comprehensive series of tests were carried out on amalgamation tailings from the ASGM in Sekotong area, West Nusa Tenggara. The tailings contain mercury up to 150 ppm, above the safe threshold, and gold up to 20 ppm which is intended to be recovered. Furthermore, mineral liberation analysis (MLA) and gravity recoverable gold (GRG) test were performed to determine the feasibility of recovering gold from the tailings. The liberation degree of the gold started from particle size of 37 \xm causes challenging to recover it. However, the GRG test confirmed that the gold was still feasible to be recovered by gravity concentration.

Mineralogical Prediction on the Flotation Behavior of Copper and Molybdenum Minerals from Blended Cu–Mo Ores in Seawater

The copper ore in Chilean copper porphyry deposits is often associated with molybdenum minerals. This copper–molybdenum (Cu–Mo) sulfide ore is generally mined from various locations in the mining site; thus, the mineral composition, oxidation degree, mineral particle size, and grade vary. Therefore, in the mining operation, it is common to blend the ores mined from various spots and then process them using flotation. In this study, the floatability of five types of Cu–Mo ores and the blending of these ores in seawater was investigated. The oxidation degree of these Cu–Mo ores was evaluated, and the correlation between flotation recovery and oxidation degree is presented. Furthermore, the flotation kinetics of each Cu–Mo ore were calculated based on a mineralogical analysis using mineral liberation analysis (MLA). A mineralogical prediction model was proposed to estimate the flotation behavior of blended Cu–Mo ore as a function of the flotation behavior of each Cu–Mo ore. The flotation results show that the recovery of copper and molybdenum decreased with the increasing copper oxidization degree. In addition, the recovery of blended ore can be predicted via the flotation rate equation, using the maximum recovery (Rmax) and flotation rate coefficient (k) determined from the flotation rate analysis of each ore before blending. It was found that Rmax and k of the respective minerals slightly decreased with increasing the degree of copper oxidation. Moreover, Rmax varied greatly depending on the mineral species. The total copper and molybdenum recovery were strongly affected by the degree of copper oxidation as the mineral fraction in the ore varied greatly depending upon the degree of oxidation.

Application of SEM Imaging and MLA Mapping Method as a Tool for Wettability Restoration in Reservoir Core Samples for SCAL Experiments

In reservoir engineering, special core analysis experiments (SCAL) are performed in the lab to evaluate the production capabilities of an oil reservoir. A critical component of SCAL experiments is core wettability restoration to its original wettability, i.e., oil wet condition. Typically, aging is performed by saturating the core with oil and aging at reservoir temperature where time is the variable in question dictating whether the resulting restored core is strongly or weakly oil-wet. In the lab, core wettability is often experimentally validated using contact angle measurements or USBM (United States Bureau of Mines) wettability tests, which are often time consuming, expensive and prone to error. In this study we developed a novel method by using Scanning Electron Microscope (SEM) and mineral liberation analysis (MLA) imaging (at low vacuum conditions) to determine the wettability of rocks saturated with reservoir fluids such as oil and brine. For this work a systematic approach was applied with comparing the SEM-MLA method against conventional methods to quantify the degree of uncertainty linked to a) wettability estimation and b) the aging time. We have used a comprehensive suite of core samples such as Berea, Silurian Dolomite and Chalk to represent the bulk of oil reservoirs in the world.

Automated Indicator Mineral Analysis of Fine-Grained Till Associated with the Sisson W-Mo Deposit, New Brunswick, Canada

Exploration under thick glacial sediment cover is an important facet of modern mineral exploration in Canada and northern Europe. Till heavy mineral concentrate (HMC) indicator mineral methods are well established in exploration for diamonds, gold, and base metals in glaciated terrain. Traditional methods rely on visual examination of >250 µm HMC material. This study applies mineral liberation analysis (MLA) to investigate the finer (<250 µm) fraction of till HMC. Automated mineralogy (e.g., MLA) of finer material allows for the rapid collection of precise compositional and morphological data from a large number (10,000–100,000) of heavy mineral grains in a single sample. The Sisson W-Mo deposit has a previously documented dispersal train containing the ore minerals scheelite, wolframite, and molybdenite, along with sulfide and other accessory minerals, and was used as a test site for this study. Wolframite is identified in till samples up to 10 km down ice, whereas in previous work on the coarse fraction of till it was only identified directly overlying mineralization. Chalcopyrite and pyrite are found up to 10 km down ice, an increase over 2.5 and 5 km, respectively, achieved in previous work on the coarse fraction of the same HMC. Galena, sphalerite, arsenopyrite, and pyrrhotite are also found up to 10 km down ice after only being identified immediately overlying mineralization using the >250 µm fraction of HMC. Many of these sulfide grains are present only as inclusions in more chemically and robust minerals and would not be identified using optical methods. The extension of the wolframite dispersal train highlights the ability of MLA to identify minerals that lack distinguishing physical characteristics to aid visual identification.

Potential Benefits in Copper Sulphides Liberation through Application of HRC Device in Ore Comminution Circuits

The article presents results of investigations on a high-pressure comminution process carried out in the roller press device, aiming at potential improvement of effectiveness of downstream beneficiation operations. The major point of interest of the paper concerned an assessment of the useful mineral liberation in relation to the volume of operating pressing force in the press device. Obtained results of mineral liberation were compared to flotation effects and downstream grinding process in a ball mill. Environmental influence in terms of dust emission was also analysed. The feed material was crushed in the high-pressure roller crusher (HRC) device under four different values of pressing force (Fsp): 3.0, 3.5, 4.0 and 4.5 N/mm2. Each product then underwent the liberation analysis, together with determination the energy savings through calculation of Bond’s working index, flotation recoveries and grinding kinetics. Results of investigations showed that both the most favourable crushing results and mineral liberation level were achieved for the highest values of operational pressing force. Nevertheless, the observed effects were less than linear together with further increasing of Fsp in HRC device. However, the obtained results of investigation unambiguously showed that pressing force affects the obtained crushing results: comminution degrees and flotation recoveries were higher while the duration of downstream grinding operation and grinding energy consumption were lower.

MULTI-LABEL CLASSIFICATION FOR DRILL-CORE HYPERSPECTRAL MINERAL MAPPING

A multi-label classification concept is introduced for the mineral mapping task in drill-core hyperspectral data analysis. As opposed to traditional classification methods, this approach has the advantage of considering the different mineral mixtures present in each pixel. For the multi-label classification, the well-known Classifier Chain method (CC) is implemented using the Random Forest (RF) algorithm as the base classifier. High-resolution mineralogical data obtained from Scanning Electron Microscopy (SEM) instrument equipped with the Mineral Liberation Analysis (MLA) software are used for generating the training data set. The drill-core hyperspectral data used in this paper cover the visible-near infrared (VNIR) and the short-wave infrared (SWIR) range of the electromagnetic spectrum. The quantitative and qualitative analysis of the obtained results shows that the multi-label classification approach provides meaningful and descriptive mineral maps and outperforms the single-label RF classification for the mineral mapping task.