Liberation Analysis Research Articles

Nanoscale mechanical property variations concerning mineral composition and contact of marine shale

Mechanical properties of shales are key parameters influencing hydrocarbon production – impacting borehole stability, hydraulic fracture extension and microscale variations in in situ stress. We use Ordovician shale (Sichuan Basin, China) as a type-example to characterize variations in mineral particle properties at microscale including particle morphology, form of contact and spatial distribution via mineral liberation analysis (MLA) and scanning electron microscopy (SEM). Deformation-based constitutive models are then built using finite element methods to define the impact of various architectures of fracture and mineral distributions at nanometer scale on the deformation characteristics at macroscale. Relative compositions of siliceous, calcareous and clay mineral particles are shown to be the key factors influencing brittleness. Shales with similar mineral composition show a spectrum of equivalent medium mechanical properties due to differing particle morphology and mineral heterogeneity. The predominance of small particles and/or point-point contacts are conducive to brittle failure, in general, and especially so when quartz-rich. Fracture morphology, length and extent of filling all influence shale deformability. High aspect-ratio fractures concentrate stress at fracture tips and are conducive to extension, as when part-filled by carbonate minerals. As fracture spacing increases, stress transfer between adjacent fractures weakens, stress concentrations are amplified and fracture extension is favored. The higher the fractal dimension of the fracture and heterogeneity of the host the more pervasive the fractures. Moreover, when fractures extend, their potential for intersection and interconnection contributes to a reduction in strength and the promotion of brittle failure. Thus, these results provide important theoretical insights into the role of heterogeneity on the deformability and strength of shale reservoirs with practical implications for their stimulation and in the recovery of hydrocarbons from them.

Conventional versus microwave-assisted roasting of sulfidic tailings: Mineralogical transformation and metal leaching behavior

Roasting is often required to convert sulfidic minerals into their sulfate and/or oxide forms with the aim to increase the extractability of targeted metals. In this study, sulfidic tailings of Neves Corvo Cu-Zn-Pb-mine (Portugal) underwent conventional roasting (CR) and microwave-assisted roasting (MR) to compare the effect of both heating technologies on the roasting behavior. Upon roasting in air, transformations of mineral phases in the tailings were studied by different techniques using quantitative X-ray diffraction, mineral liberation analysis, Raman spectroscopy and thermogravimetry-differential scanning calorimetry coupled to mass spectrometry. Also, the leaching behavior of elements from the roasted tailings was assessed in water. It was shown that CR and MR induce different reaction pathways for mineral transformations during roasting. While CR led to indirect pyrite oxidation through intermediate sulfate formation, direct pyrite oxidation was the main transformation pathway during MR. This change in reaction pathway can be attributed to the mineral-selective heating induced by microwaves, which in particular accelerates the oxidation rate of pyrite. In agreement with the proposed roasting mechanism, the leaching behavior in water showed that CR resulted in a higher extraction of Cu, Zn, Pb, As and Fe from the tailings – since their sulfate phases are more abundant – compared to MR at the same roasting temperature. Overall, tailings treated by CR and MR within the temperature ranges of 500 °C to 550 °C for 1 h gave optimal leaching efficiencies of the studied metals (water leaching at room temperature for 30 min; stirring speed of 600 rpm; solid-to-liquid ratio of 10 mL · g−1). Furthermore, thermodynamic equilibrium calculations showed that hydrolysis of soluble Fe(III) species strongly controls the pH of the leachates. In comparison to MR tailings, more acidic leachates were generated for CR tailings because of a more pronounced formation of ferric sulfate.

Deep convolutional neural network for 3D mineral identification and liberation analysis

Mineral liberation analysis (MLA) is an automated mineral analysis system that identifies minerals in polished two-dimensional (2D) sections of drill or lump cores or particulate mineral matter. MLA allows a wide range of mineral characteristics to be investigated, including fragment size, mineral abundance, and liberation. To date, this analysis has been primarily limited to two-dimensional (2D) section information. In this study, we describe an MLA workflow that enables the extension of MLA into 3D via the utilization of 3D X-ray microcomputed tomography and convolutional neural network (CNN) guided by M4-Tornado micro-X-ray fluorescence (micro-XRF) data. With the combination of 3D greyscale micro-CT data with several 2D identified element mappings, the state-of-the-art CNN architecture called EfficientU-Net-b3 is trained and tested for multimineral segmentation on both an intact complex iron ore sample and the corresponding crushed fragments. Compared to traditional manual segmentation methods, where only greyscale thresholds are selected by humans, CNN-based segmentation takes the information from unbiased microXRF and extracts not only the greyscale values but also the texture features from the image. After the segmentation of the 3D micro-CT datasets, several mineral liberation analyses are performed in the 3D domain, as well as 2D slices that are uniformly selected from the 3D segmented fragments data. The results from 2D and 3D MLA demonstrate that the 2D analysis results are heterogeneous and significantly different (up to a 14 % difference in the association indicator matrix) from the 3D analysis results. The loss of mineral information from 2D could influence ore body characterization and the proposed mineral processing procedure. Overall, the proposed workflow provides a digital mineral framework for 3D MLA for future ore characterization applications.

Quaternary ironstones in the Xingu River, eastern Amazonia (Brazil)

AbstractUsing a multimethod approach, including polarized light microscopy (PLM), scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS), SEM with mineral liberation analyzer (MLA), X-ray diffraction (XRD), and Raman spectroscopy, we examined sub-recent ferruginous crusts in the Xingu River in the Amazon Basin that have formed since the Early Pleistocene (<1.2 Ma), as indicated by (U-Th)/He dating of goethite. Although now preserved as goethite, the size and form of the smallest components of the ironstone (nanorods) and the nature of isomorphic substitution in the goethite point to very early transformation of the original precipitate, an unstable hydrous ferrous oxide (HFO) mineral, into goethite. The fine, multiply undulating laminae of the ironstone contain abundant filamentous microbial molds and casts that together support identification of the crusts as ferruginous microbialites and suggest a role of bioinduction/bioinfluence in ironstone precipitation, although inorganic precipitation is also evident. The Xingu Quaternary ironstones are the first evidence of ferruginous microbialite in a modern freshwater system in South America and may hold clues to the recent history of the Xingu River.

Physicochemical and environmental characteristics of alkali leaching residue of wolframite and process for valuable metals recovery

Physicochemical and mineralogical characteristics of an alkali leaching residue of wolframite were studied by XRD, SEM−EDS, chemical phase analysis, mineral liberation analyzer (MLA), and TG−DSC methods. Batch leaching tests, toxicity characteristic leaching procedure (TCLP) tests and Chinese standard leaching tests (CSLT) were conducted to determine the environmental mobility of toxic elements. The results show that, due to the high contents of W, Fe, Mn, Sn, and Nb, the residue is with high resource value, but the content of a toxic element, As, is also high. The existing minerals of the investigated elements mainly occur as monomer particles, but it is difficult to extract these valuable metals by conventional acid leaching due to their mineral properties. The release of As increases over time in acidic environment. The leaching concentration of all investigated harmful elements through TCLP is within the limiting value, while the leaching concentration of As through CSLT exceeds the limiting value by more than 4 times, so the residue is classified as hazardous solid waste based on the Chinese standard. A process for valuable metals recovery from this residue was proposed. Preliminary experimental results indicated that the main valuable metals could be extracted effectively.

Mineralogical Characteristics of Pegmatite Tailings and Beneficiation Assessment of Pollucite in Recovering Cesium

The technological mineralogical characteristics of cesium-containing minerals in tailings were examined by means of chemical analysis, the energy spectrum analysis method, and MLA (mineral liberation analyzer) to determine the element content, phase analysis, associated mineral components, degree of liberation, particle size, etc. The results showed that the samples mainly contained spodumene, quartz, feldspar, mica, and other minerals. Pollucite was the main cesium-containing mineral in the sample, which had a cesium oxide content that was as high as 34.58%. The mineral content of pollucite in the sample was relatively low—only 1.23%. The pollucite monomer content and the amount of rich intergrowth was 85.25%, and the metal distribution of cesium in the +0.074 mm sample was as high as 87.06%. Spodumene was the main mineral associated with pollucite. The beneficiation evaluation of this tailing sample was conducted using a combined process that integrated desliming, magnetic separation, and froth flotation, and a pollucite concentrate containing 4.45% Cs2O was obtained with a 63.71 recovery rate. This indicates that little pollucite was removed by means of desliming and magnetic separation before froth flotation recovery, but during the froth flotation stage in spodumene and feldspar, a large pollucite loss was observed. Therefore, to improve pollucite recovery, a pollucite-specific adsorption reagent should be synthesized.

Deep Insight on the Occurrence Feature of Iron Minerals in a Cyanide Leaching Residue and Its Effective Recovery with Magnetic Separation

The occurrence features of ultrafine iron minerals in a cyanide leaching residue produced from a superlarge gold mining company in Yunnan Province were determined with chemical composition analysis, iron phase analysis, and mineral liberation analysis (MLA). The results show that the residue contains 26.74% iron, mainly occurring in the form of magnetite (26.33%) and limonite (69.41%), in which 67.40% magnetite and 73.00% limonite particles are fully liberated with particle sizes ranging from 9.6 µm to 75.0 µm. The rest are adjacent and wrapped intergrowths. Low-intensity magnetic separation and pulsating high-gradient magnetic separation were, respectively, proposed to recover magnetite and limonite from the residue, and under the optimized conditions, a high-grade magnetite concentrate assaying 64.05% Fe with 85.59% magnetite recovery and a qualified limonite concentrate assaying 50.94% Fe with 54.33% limonite recovery were, respectively, produced. The iron recovery for −30 µm fraction in the magnetite and limonite concentrates reached as high as 51.46%. It was found that the iron recovery for −30µm ultrafine fraction is lower than those of coarser fractions, as a result of the relatively enhanced hydrodynamic drag acting onto the particles, compared with the magnetic force. Entrainment occurs between the ultrafine iron minerals and gangues, thereby reducing the iron grade for the ultrafine fraction. This research outcome would provide a valuable reference for the economic and effective utilization of iron resources from such residues.

Prediction of iron ore mineral liberation behavior using the Andrews–Mika diagram and beta distribution

A combined grinding and liberation model was studied to predict the liberation characteristics of iron ore comminuted by a ball mill. Comminution characteristics were obtained using the one-size-fraction method; then, the iron ore samples were crushed and separated into several narrow-size fractions by screening. The size fractions were further divided into three classes by magnetic separation, namely concentrate, middling, and tailings. Subsequently, various size classes were subjected to ball milling, and the results were analyzed in the kinetic grinding model. The mineralogical textures of the ground products were analyzed using mineral liberation analysis. The beta distribution and Andrews–Mika diagram characterized the distribution of the iron content within the size fractions. The breakage characteristics of the iron ore samples varied slightly with the iron content. However, the liberation characteristics were well-described by adjusting the four parameters of the beta distribution. The variation in grinding kinetics with composition and liberation model parameters was used in the combined liberation–comminution model to predict the evolution of the size–composition matrix as grinding proceeded. The predicted results align with the experimental results. The developed model can construct a yield–recovery graph and calculate the liberation efficiency to determine the size reduction threshold for efficient separation.

Mineralogical Characteristic and Beneficiation Evaluation of a Ta-Nb-Li-Rb Deposit

In order to rationally develop and utilize a Ta–Nb–Li–Rb rare metal deposit in Jiangxi Province, the mineralogical characteristics of the ore, such as chemical composition, mineral composition, modes of occurrence of major elements, and dissemination characteristics of major minerals, were investigated in detail based on optical microscopy analysis, chemical analysis, X-ray diffraction analysis, artificial panning, mineral liberation analysis, and electron probe microanalysis. The results reveal that the main useful elements in the ore are tantalum, niobium, lithium, and rubidium. Niobium and tantalum are mainly found in the mineral form of columbite. Columbite has particle sizes ranging from 0.5 mm to 0.012 mm, with the most common sizes being 0.3 to 0.044 mm. Intergranular dispersion accounts for 73.92% of the embedding in columbite, whereas inclusions account for 26.08%. Lithium is found mostly in zinnwaldite, while rubidium is found primarily in feldspar and zinnwaldite, both in a homogenous distribution. The beneficiation evaluation of this ore was conducted based on the mineralogical characteristic, and it indicates that the tantalum-niobium–lithium–rubidium rare metal resources, as well as the feldspar and quartz non-metallic resources in the ore, can be effectively and comprehensively recovered using gravity, magnetic, and flotation separation methods. A staged grinding and separating process was adopted which could produce tantalum–niobium mineral concentrates (18.34% Ta2O5 at a recovery of 47.65% and 41.33% Nb2O5 at a recovery of 69.96%), zinnwaldite concentrate (2.41% Li2O and 0.80% Rb2O at a recovery of 81.82%) and other concentrates such as cassiterite, topaz, galena, sphalerite, and feldspar. This study provides suggestions for the rational development and utilization of the deposit and provides a reasonable level of recovery prediction.

A typical case study from smelter-contaminated soil: new insights into the environmental availability of heavy metals using an integrated mineralogy characterization.

Mineralogy was an important driver for the environmental release of heavy metals. Therefore, the present work was conducted by coupling mineral liberation analyzer (MLA) with complementary geochemical tests to evaluate the geochemical behaviors and their potential environmental risks of heavy metals in the smeltercontaminated soil. MLA analysis showed that the soil contained 34.0% of quartz, 17.15% of biotite, 1.36% of metal sulfides, 19.48% of metal oxides, and 0.04% of gypsum. Moreover, As, Pb, and Zn were primarily hosted by arsenopyrite (29.29%), galena (88.41%), and limonite (24.15%), respectively. The integrated geochemical results indicated that among the studied metals, Cd, Cu, Mn, Pb, and Zn were found to bemore bioavailable, bioaccessible, and mobile. Based on the combined mineralogical and geochemical results, the environmental release of smelter-driven elements such as Cd, Cu, Mn, Pb, and Zn were mainly controlled by the acidic dissolution of minerals with neutralizing potential, the reductive dissolution of Fe/Mn oxides, and the partial oxidation of metal sulfide minerals. The present study results have confirmed the great importance of mineralogy analysis and geochemical approaches to explain the contribution of smelting activities to soil pollution risks.

The Analysis of Trade Liberalization and Nutrition Intake for Improving Food Security across Districts in Indonesia

The debate on the effect of trade liberalization on food security poses solid arguments, both in favor as well as against the issue. This study aims to analyze the linkages between trade liberalization (measured using food import tariff exposure) and food security (measured using nutrition intake) in the case of Indonesia. The national food import tariff is decomposed into district-level import tariff exposure and is analyzed based on sectoral tariffs such as agriculture tariffs and food manufacture import tariffs. The analysis employs panel data of 496 Indonesian districts and postulates an association between trade and food security by using fixed-effect regression. By analyzing the effects of tariff exposure towards food consumption in all districts and grouping the districts into 5 (five) islands, we can contribute to the literature on trade liberalization and food security. First, it is found that import tariff exposure is negatively impacting nutrition intake and each sector has a different effect on each nutrition intake. Furthermore, the impact of manufacturing tariffs on calorie and protein intake is slightly higher than that of agriculture tariffs. Second, it is shown that both sectoral import tariffs’ effects vary across islands in Indonesia. Furthermore, the research is expected to contribute to and become a reference for the government in regulating tariffs and other trade liberalization schemes to support households to be food secure.

MLA and optical microscopy as complementary techniques to the iron ore geometallurgical studies

Mineral liberation is an important variable to be considered in the iron ore geometallurgical studies, especially since it provides information leading to the understanding of the ore’s behaviour in the beneficiation process, mainly when harder ores are concerned. Nowadays, the professionals and researchers in the mineral industry have been using complementary techniques for mineralogical characterization. In this way, Mineral Liberation Analyser (MLA) and optical microscopy are amongst the most efficient and important tools in these studies. Together, these techniques can provide information leading to the development of geometallurgical models, including the degree of quartz liberation, mineral modal composition, mineralogical association and particle and mineral size distribution, as well as the spectrum of mineral liberation either by free surface or particle composition. The purpose of this study is to compare the degree of quartz liberation in four different iron ore types observed in optical microscopy and MLA. It also assesses the influence of mineral liberation in the quality of the resulting concentrate, according to the SiO2 content. All the results of the various quartz liberation degrees, determined by both MLA and optical microscopy were very close, as well as the correlation between the mineral liberation and the ore’s response in the flotation process. The investigation provided evidence that the mineral liberation study is an important tool in the prediction of the ore’s behaviour in the beneficiation process.

Comparative Analysis of Trade Liberalization, CO2 Emissions, Energy Consumption and Economic Growth in Southeast Asian and Latin American Regions: A Structural Equation Modeling Approach

This study compares the nexus among trade liberalization, CO2 emissions, energy consumption, and economic growth in Southeast Asian and Latin American countries. We apply the structural equation modeling approach for estimation analysis of the data from 1991 to 2018. The empirical findings of this study validate that trade has a positive and statistically significant effect on energy consumption, CO2 emissions, and gross domestic product (GDP) in Southeast Asian countries. Whereas in Latin American countries, trade shows a positive insignificant impact on energy consumption, but the coefficients for both CO2 emissions and GDP are positive and statistically significant. Energy consumption also exhibits a positive significant effect on CO2 emissions and a positive statistically insignificant effect on GDP in the Southeast Asian region. However, in Latin American countries, energy consumption predicts a positive and statistically significant impact on both CO2 emissions and GDP. Whereas, CO2 emissions indicate a positive significant effect on GDP in both regions. Therefore, each country’s government in both areas should formulate appropriate policies to promote green technologies in the production and exports, which could help economies to achieve a clean environment and sustainable long-term development.

Process Mineralogy of the Tailings from Llallagua: Towards a Sustainable Activity

There are significant tin reserves in the dumps and tailings from Llallagua. Currently, this waste is being processed using gravity concentration or a combination of gravity concentration with a final stage of froth flotation. A process mineralogy study of the tailings and their products after processing in Llallagua was carried out to determine the failings of the processing system in order to contribute to designing an improved new processing scheme. The mineralogy of the feed tailings, concentrate, and final tailings was determined by X-ray diffraction, scanning electron microscopy, and mineral liberation analysis. The tailings were composed of quartz, tourmaline, illite, K-feldspar, plagioclase, cassiterite, rutile, zircon, and monazite. The concentrate essentially contains cassiterite (57.4 wt.%), tourmaline, quartz, hematite, rutile and rare earth minerals, mainly monazite and minor amounts of xenotime and florencite. The concentrate contained 52–60 wt.% of SnO2 and 0.9–1.3 wt.% REE. The final tailings contained 0.23–0.37 wt.% SnO2 and 0.02 wt.% of Rare Earth Elements (REE). Only 57.6 wt.% of cassiterite from the concentrate was liberated. The non-liberated cassiterite was mainly associated with quartz, tourmaline, and rutile. The average grain size of monazite was 45 µm and 57.5 wt.% of this was liberated. In other cases, it occurs in mixed particles associated with tourmaline, quartz, cassiterite, and muscovite. To improve the sustainability of this mining activity, the concentrate grade and the metal recovery must be improved. Reducing the particle size reduction of the processed tailings would increase the beneficiation process rates. In addition, the recovery of the REE present in the concentrate as a by-product should be investigated.

Investigation of Sensor-Based sorting and selective comminution for pre-concentration of an unusual parisite-rich REE ore, South Namxe, Vietnam

The South Namxe deposit in Vietnam contains unusually high quantities of parisite, in addition to minor quantities of other fluorocarbonates, such as synchysite and bastnaesite. Together these minerals constitute the main REE-bearing minerals. This carbonatite-related deposit presents tabular (dykes) or lens-form ore bodies, up to several tens of meters wide and tens to hundreds of meters in length, that are hosted in Permian limestone and Triassic basalts. The main gangue minerals in the ore bodies are from the barite-celestine solid solution series, ankerite and calcite. It was considered necessary to assess the different grain characteristics presented by the presence of parisite intergrowths and its association with minerals of the barite-celestine solid solution series to structure a probable initial beneficiation strategy. Mineral liberation analysis revealed that an optimal liberation particle size between 45 µm and 90 µm could be achieved without overgrinding the material. Additionally, it showed a strong mineral association between fluorocarbonates, baryto-celestine, and calcite. Grinding below 100 µm is necessary. One substantial energy saving potential is removing the host rock prior to grinding. The potential for pre-concentration with sensor-based sorting and selective comminution is investigated in a pre-study. Sensor-based sorting using X-ray transmission resulted in an enrichment of REE by a factor of 4, a reduction of the mass stream down to approximately 30%, and a loss of rare earths below 2%. Selective comminution using a pin mill, at a circumferential speed of 20 m/s, yielded a recovery of 96.5% of REE minerals and allowed rejection of 27% of barren material. This shows that both selective comminution and sensor-based sorting can be considered as complementary beneficiation steps when processing these REE ores.

Upgrading of Low-Grade Colombian Coals via Low-Cost and Sustainable Calcium Nitrate Dense Media Separation.

Wet coal beneficiation in Colombia is prohibitive due to the high cost and scarcity of commonly used dense media. The practical value of this study is that it demonstrates for the first time that a common fertilizer, calcium nitrate, can be used in the beneficiation of low-grade Colombian coals. Three high-ash low-grade Colombian coals (Valle, Cundinamarca, and Antioquia) commonly used in Colombian sugar mill stoker furnaces were tested. Coal mineralogy and prevalence were analyzed before and after washing using mineral liberation analysis. The swelling potential of the coals was assessed using a novel application of thermal mechanical analysis (TMA) and an ash fusion oven (AFO). Calcium nitrate reduced ash levels across all size fractions, even for high-ash coals like Valle (29% to below 7%) to acceptable levels for coke manufacturing or pulverized fuel combustion. The novel use of TMA and AFO to analyze coal swelling demonstrated that swelling varies under constrained and unconstrained conditions and the small sample size allows for rapid testing of coal swelling. This study has demonstrated that the use of common fertilizers can allow beneficiation to become a processing option for low-grade coals in Official Development Assistance countries where conventional dense media is prohibitively expensive.

2D-3D Divergence in Liberation Analysis of Ore Particles

2D-3D Divergence in Liberation Analysis of Ore Particles

A simulation-based stereological correction method for assessment of volumetric liberation and surface exposure of ore particles

• A simulation-based stereological correction method was developed. • First, a database of liberation distributions is established by simulation. • Then, 3D liberation is estimated from 2D liberation, with reference to the database. • Volumetric liberation and surface exposure bias can be corrected. In assessment of the volumetric liberation and surface exposure of ore particles, two-dimensional (2D) analysis, such as the widely used scanning electron microscope and energy dispersive X-ray (SEM/EDX)-based analysis, results in stereological bias with respect to the three-dimensional (3D) reality. Thus, a simulation-based stereological correction method for accurate assessment of volumetric liberation and surface exposure was developed. The method utilizes a pre-established database of numerically simulated binary particles to estimate 3D composition (or exposure) distributions only from measurable 2D composition (or exposure) distributions. Among the notable features of the method are the relatively small amount of 2D-distribution input data required, and the rapidity of the analysis. Experimental validation, and ex-post analysis of previously published research results, showed high estimation accuracy for various types of particles (including actual ore samples) examined in previous studies. In addition, the method is suitable for post analysis of SEM/EDX-based particle sectional liberation analysis.

The spatial association of accessory minerals with biotite in granitic rocks from the South Mountain Batholith, Nova Scotia, Canada

Abstract We use mineral liberation analysis (MLA) to quantify the spatial association of 15,118 grains of accessory apatite, monazite, xenotime, and zircon with essential biotite, and clustered with themselves, in a peraluminous biotite granodiorite from the South Mountain Batholith in Nova Scotia (Canada). A random distribution of accessory minerals demands that the proportion of accessory minerals in contact with biotite is identical to the proportion of biotite in the rock, and the binary touching factor (percentage of accessory mineral touching biotite divided by modal proportion of biotite) would be ~1.00. Instead, the mean binary touching factors for the four accessory minerals in relation to biotite are: apatite (5.06 for 11,168 grains), monazite (4.68 for 857 grains), xenotime (4.36 for 217 grains), and zircon (5.05 for 2876 grains). Shared perimeter factors give similar values. Accessory mineral grains that straddle biotite grain boundaries are larger than completely locked, or completely liberated, accessory grains. Only apatite-monazite clusters are significantly more abundant than expected for random distribution. The high, and statistically significant, binary touching factors and shared perimeter factors suggest a strong physical or chemical control on their spatial association. We evaluate random collisions in magma (synneusis), heterogeneous nucleation processes, induced nucleation in passively enriched boundary layers, and induced nucleation in actively enriched boundary layers to explain the significant touching factors. All processes operate during the crystallization history of the magma, but induced nucleation in passively and actively enriched boundary layers are most likely to explain the strong spatial association of phosphate accessories and zircon with biotite. In addition, at least some of the apatite and zircon may also enter the granitic magma as inclusions in grains of Ostwald-ripened xenocrystic biotite.

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.