Hematite Particles Research Articles

Reduction Mechanism of Fine Hematite Ore Particles in Suspension

In order to understand the pre-reduction behaviour of fine hematite particles in the HIsarna process, change of morphology, phase and crystallography during the reduction were investigated in the high temperature drop tube furnace. Polycrystalline magnetite shell formed within 200 ms during the reduction. The grain size of the magnetite is in the order of magnitude of 10 µm. Lath magnetite was observed in the partly reduced samples. The grain boundary of magnetite was reduced to molten FeO firstly, and then the particle turned to be a droplet. The Johnson-Mehl-Avrami-Kolmogorov model is proposed to describe the kinetics of the reduction process. Both bulk and surface nucleation occurred during the reduction, which leads to the effect of size on the reduction rate in the nucleation and growth process. As a result, the reduction rate constant of hematite particles increases with the increasing particle size until 85 µm. It then decreases with a reciprocal relationship of the particle size above 85 µm.

Sunlight-triggered synergy of hematite and Shewanella oneidensis MR-1 in Cr(VI) removal

Hematite is usually considered as a terminal electron acceptor for dissimilatory metal-reducing bacteria (DMRB), such as Shewanella oneidensis MR-1. However, hematite is also a semiconductor with visible light response. How the photocatalytic activity of hematite affects its electrical interplay with DMRB, as well as its role in relevant biogeochemical processes under sunlight, is still unclear. In this study, we investigated the effect of hematite on Cr(VI) removal by S. oneidensis MR-1 in the dark versus under stimulated sunlight using both batch experiments and photoelectrochemical analysis in a solar-assisted microbial photoelectrochemical system with a hematite photoanode covered by S. oneidensis MR-1. Under the dark conditions, hematite at low mineral-to-cell ratios can promote Cr(VI) removal through adsorbing both Cr(VI) and bacteria on/near hematite surface, which facilitates Cr(VI) bio-reduction and also alleviates self-poisoning processes of cells with time. However, as mineral-to-cell ratios reach a high level, hematite particles may cover cell surface and impact Cr(VI) bio-reduction, leading to the decreased Cr(VI) removal with increasing hematite particles. Under simulated sunlight, S. oneidensis MR-1 generates electrons from lactate metabolism and utilizes them to fill photoexcited holes in hematite, generating photoexcited electrons to reduce Cr(VI). Thus, in addition to directly enzymatic reduction of Cr(VI), the new light-triggered electron transfer pathway: lactate → S. oneidensis MR-1 → hematite → Cr(VI) further increases Cr(VI) removal and lactate metabolism. Also, the time-dependent cell survival is increased by the presence of hematite under the simulated sunlight, probably owing to the promoted Cr(VI) reduction and accumulation of Cr(III)-products on hematite surface. Moreover, organic hole scavenger, such as Ethylenediaminetetraacetic acid (EDTA), can further enhance Cr(VI) removal by hematite and S. oneidensis MR-1 under light irradiation. The photoelectrochemical results confirm that the light-triggered electron transfer pathway can be promptly and repeatedly produced upon illumination, and the rapid decrease of photocurrents after spiking Cr(VI) indicates Cr(VI) reduction by the photogenerated electrons from hematite. These findings suggest that semiconducting minerals, like hematite, can harvest solar energy to boost microbial metabolism and contaminant transformation by non-phototrophic, electroactive bacteria, which in turn increases bacterial tolerance toward toxic compounds in surrounding environments.

Tannin: An eco-friendly depressant for the green flotation separation of hematite from quartz

Reverse cationic flotation is the most known beneficiation method for the separation of fine hematite particles from silicates. In this process, the depression of the hematite surface is an essential factor. Thus, the development of environmentally friendly depressants plays a critical role. Tannin (TA) as a natural and eco-friendly organicreagent has not yet been considered for such a purpose. Through the reverse cationic flotation, the depression effect of TA was investigated by single and mixture of minerals. Micro-flotation tests and wettability analysis based on contact angle measurements by the captive bubble method (CBM) were conducted. The surface adsorption mechanism of TA on the hematite and quartz was explored through turbidity, zeta-potential measurements, surface adsorption tests, and Fourier transform infrared (FT-IR) analyses. The micro-flotation results indicated that TA could selectively depress more than 90% of hematite, while its effect on quartz floatability was negligible (<8% depressing). Surface wettability analysis demonstrated that TA in the presence of 30 mg/L collector could significantly increase the work of adhesion of hematite from 135.5 to 143.1 erg/cm2, whereas it increased the work of adhesion of quartz from 117.1 to 120.7 erg/cm2. Surface adsorption analysis depicted that in the presence of 100 mg/L TA, the adsorption amount of TA on the hematite surface was 0.99 mg/g, while this amount for quartz was 0.17 mg/g (around 6 times lower than hematite). Turbidity measurements, applied to clarify the aggregation – dispersion behavior of pure minerals in the TA presence, showed that TA had a dispersion effect on the quartz particles, whereas TA caused hematite aggregation. Surface analyses proved that TA selective adsorption occurred on the hematite surface mainly by chemisorption. In contrast, poor physical adsorption was the main interaction between TA and the quartz surface.

Rapid Microwave Method for Synthesis of Iron Oxide Particles under Specific Conditions

The advantages of microwave technology over conventionally conducted experiments are numerous. Some of them are reduction in reaction time, a higher degree of process control, repeatability, and work safety. Microwave synthesis routes require a complete description of the experimental details, instrumentation, and design program of a microwave oven used in the experiments. In this work, microwave-assisted hydrothermal synthesis of hematite (α-Fe2O3) particles from 0.1 M FeCl3 solution in highly alkaline media with heating in a microwave oven at continuous microwave emission of 800 W at 150 °C, 200 °C, and 250 °C for 20 min are presented. Also, the influence of the percentage of the addition of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) on the composition, size, and shape of the final product was investigated. The samples precipitated at 150 °C formed a final product consisting of goethite (α-FeOOH) and hematite particles in contrast to the those precipitated at 200 °C and 250 °C where pure hematite phase was obtained. In these synthesis routes, the CTAB caused to slow down the rate of the goethite-to-hematite transformation process at temperatures at 200 °C but did not affect the transformation at 250 °C.

Selective bioflocculation of ultrafine hematite particles from quartz using a biosurfactant extracted from Candida stellata yeast

ABSTRACT In the last decade the mineral industry has been working in order to face its biggest challenge: The processing of ultrafine mineral particles. Several techniques and processes have been used to improve its recovery, without success. Bioflocculation has been considered as a potential tool in order to process these particles. The aim of the present study was to evaluate the flocculation of ultrafine hematite particles contained in iron ore tailing slimes, using the biosurfactant (BS) extracted from the Candida stellata yeast. The analysis of the mineral-biosurfactant interaction was conducted through FTIR spectroscopy, zeta potential, and surface tension measurements. The flocculation analysis was made using a laboratory jar-test. The FTIR and zeta potential investigations indicated adsorption of the BS onto hematite surface. The biosurfactant modified the surface properties of hematite and a reversal charge point was observed at pH 3.3. Thus, bioflocculation of pure hematite particles (recovery of around 90%) was conceivable under pH 3.0, and using between 75 and 100 mg.L−1 of BS. Lastly, bioflocculation of the tailing slimes sample was conducted: The previous results were confirmed, which means that a selective flocculation was pointed out at pH 3.0, achieving an iron recovery and grade of around 92% and 59%.

Effect of electrostatic interaction on the retention and remobilization of colloidal particles in porous media

We investigate the effect of pH on external hematite colloidal particles entrapment and remobilization by core-flood experiments combined with X ray computed tomography. Suspensions of calibrated hematite colloidal particles were injected into Bentheimer sandstones sample, composed mainly of well-sorted quartz and small clay fraction (up to 1 wt%), consisting mainly of kaolinite. We have found that permeability impairment due to an external cake build-up can be reversed when pH exceeds the point of zero charge of hematite particles. This effect could be successfully interpreted by the switching of the surface charge of hematite particles from positive to the negative, similar to the rock surface. The experimentally verified pH-controlled electrostatic retention and remobilization technique can be extended to other colloidal particles, having pH-dependent surface charge, including natural clay minerals in hydrocarbon and geothermal reservoirs. Therefore, varying pH of injected fluid can be applied for targeted external cake build-up and transportation of colloidal particles within a reservoir.

Numerical Investigation of Hematite Flash Reduction-biomass Steam Gasification Coupling Process

The flash ironmaking process is a novel ironmaking technology; the direct use of biomass as the reductant and fuel in this process can take full advantage of the heat and syngas produced during the biomass gasification. This study establishes a three-dimensional computational fluid dynamics model that incorporates turbulent flow, mass transfer, and heat transfer to describe the complex gas-particle reaction behavior of the hematite flash reduction-biomass steam gasification (FR-BSG) coupling process in an entrained flow reactor to explore its feasibility. The temperature and species distributions in the FR-BSG coupling process are analyzed, and the effects of steam/carbon molar ratio (S/C) and ore/biomass mass ratio (O/B) are investigated. The results show that the reduction degree of hematite particles reaches 76.67% in the residence time of 1.65 s under the conditions of S/C=0.1, O/B=1.0 and T=1673 K. The increase of S/C can enhance the production of H2 but reduce the molar fractions of H2 and CO in biomass syngas, which leads to the decrease of hematite reduction degree. A higher reduction degree of hematite and lower carbon conversion of biomass can be obtained at lower O/B values. These results provide a theoretical basis for the use of biomass as energy in flash ironmaking technology.

Development of a highly efficient selective flocculant based on functionalized β‐cyclodextrin toward beneficiation of low‐quality iron ore

AbstractThe present work is focused on the development of a novel flocculant for selective flocculation of iron ore using functionalized β‐cyclodextrin (β CD). β CD has been modified by esterification reaction with methacrylic anhydride (MAh) to form β CD methacrylate (CD‐Meth). After that, a three‐dimensional polymeric network structure has been prepared by free radical polymerization of CD‐Meth with copolymeric chain of poly (acrylamide‐co‐acrylic acid) through grafting. The synthesized material has been characterized in detail. It has been found that the developed material has promising selectivity toward the hematite particles and also demonstrates faster settling of hematite particles. The developed material is found to be superior in all aspects than that of conventional selective flocculant used for iron ore beneficiation (i.e., starch).

Size effect of hematite particles on the Cr(VI) reduction by Shewanella oneidensis MR-1

Microorganisms are commonly bonded to various soil minerals, which may influence the redox processes and bacterial metabolism. However, little is known about the impact of particle size of soil minerals on these redox processes in the subsurface environment. In this study, the Cr(VI) bioreduction by Shewanella oneidensis MR-1 (S. oneidensis) was investigated in the presence of various hematite (α-Fe2O3) particles with average diameters of 1.0 µm (hem-1 µm) and 80.0 nm (hem-80 nm) under different pH conditions. Fourier transformed infrared spectroscopy coupled with two-dimensional correlation spectroscopy (FTIR-2D-COS) analysis and isothermal titration calorimetry (ITC) were used to explore the interaction between S. oneidensis and hematite and monitor the bacterial metabolic activity, respectively. X-ray photoelectron spectroscopy (XPS) was used to elucidate the Cr(VI) removal mechanisms. Our results showed that 78% of chromate can be reduced to Cr(III) by S. oneidensis alone. Whereas, chromate reduction rates were 62% and 85% in the presence of hem-1 µm and hem-80 nm, respectively. The enhancement of Cr(VI) reduction by S. oneidensis-hem-80 nm complex may be due to the large surface area as well as the positive charge of hem-80 nm at neutral pH, which influences the physical contact between S. oneidensis and iron oxides. The microcalorimetric results showed that both hem-1 µm and hem-80 nm promoted the normal physiological functions of S. oneidensis. XPS confirmed the gradual FeCr2O4 formation and Fe(II) depletion during the Cr(VI) reduction process. This work expands our understanding of microbial-mineral interaction and its role in Cr(VI) removal mechanisms in the subsurface environment.

Study of mechanical properties and wear behavior of aluminum 6061 matrix composites reinforced with Hematite and Titania

Abstract Aluminium based metal matrix composites with several reinforcement (Hybrid MMC’s) have countless advantages of satisfying current requirement of engineering applications due to their enhanced mechanical properties like tensile strength, hardness, toughness etc. The functioning of these type of material depend on the choice of right combination of filler particle. This research work deals with examination on mechanical behaviour of aluminium alloy (AA6061) composites fabricated with hematite and titanium dioxide particles. Semi-automatic stir casting technique was employed for fabrication of aluminium based hybrid composites by changing hematite in 2, 3, 4% by weight and titanium dioxide 1, 3, 5% by weight. A nine composites sample plates were fabricated. As per standard dimensions of ASTM, the sample specimen was cleaned by polishing over emery paper. Physical properties (density and void content), mechanical properties such as impact strength, tensile strength, hardness and sliding wear behaviour (Pin on disc tribometer) characterisation were carried out and examined. The Taguchi experiment design was used to develop experimental runs have input parameter sliding distance (1000, 1500, 2000 m), normal load (10, 15, 20 N) and reinforcement contents (2–4% by wt. Fe2O3 and 1–5% by wt. % TiO2). The worn surface structure studies were carried out to know the mechanism of the wear using Field Emission Scanning Electron Microscope (FESEM) along with Energy-dispersive X-ray spectroscopy (EDS) which indicate elemental composition and dispersion on the material surface.

Analysis of hematite attrition in a grid jet apparatus

Particulate attrition is of interest for novel carbon-capture processes such as chemical looping combustion because the makeup cost of oxygen carrier is a significant portion of operating cost. Thus, models to study and predict attrition of various oxygen carriers in fluidized bed systems are being developed. One of the regions of concern in fluidized bed systems is the high-velocity jet region near gas distributors in a fluid bed. This work studies the attrition of hematite particles using a modified ASTM apparatus to measure the particle size distribution throughout the experiment. Bed weight and gas velocity were varied. Hematite particles above the corresponding threshold value had a severe variation of particle size distributions which decreased with time. Weight fractions of the sieves over time were fit to a linear, time-variant population balance model to offer insight into particle attrition. The first-order rate constant was modified as a decaying exponential.

Flower-Like α-Fe₂O₃ for Removal of Heavy Metals from Wastewater.

In the present work flower-like, α-Fe₂O₃ were synthesized by ethylene-glycol mediated polyol method. The synthesized flower-like, α-Fe₂O₃ were separated cadmium (Cd2+) chromium (Cr6+) and lead ions (Pb2+) from wastewater. XRD pattern and FESEM images show the obtained sample is pure hematite and flower-like nanostructures average particle sizes 4.0 μm. The BET specific surface area was 47.55 m²g-1. Adsorption experiments were investigated the adsorbent dose, influence pH of the metal ions, sorption times and initial concentrations of heavy metal ions. High efficiency of Cd2+, Cr6+ and Pb2+ removal occurred at pH 7.0, 3.0 and 5.5, respectively. The adsorption equilibrium study showed that the heavy metal ions adsorption of flowers like α-Fe₂O₃ followed a Langmuir and Freundlich isotherm model. The heavy metal ions adsorption equilibrium data were followed to the Langmuir model. The maximum adsorption capacities were 16.95, 22.22 and 25.64 mg g-1 for Cd2+, Cr6+ and Pb2+ ions respectively. This work determines that the synthesized flower-like α-Fe₂O₃ is proposed as an efficient nano-adsorbent for wastewater treatment.

Investigation of potassium and copper decorations of Carajás hematite on coal-fuelled chemical looping combustion performance

Coal fuelled-chemical looping combustion (CF-CLC) is a novel and promising technology for CO2 mitigation. Reactive, cheap and environmental-friendly oxygen carriers (OC) are crutial for the development of CF-CLC. Carajás hematite is high grade iron ore with the largest reserve in the world, and its CF-CLC performance is examined in this work. Modifications of the Carajás hematite with K2CO3 and CuO were performed and the effects of the modifications were evaluated. The results show that Carajás hematite was moderately reactive and could be potential OC for CF-CLC. Decoration of the Carajás hematite with K2CO3 effectively improved carbon conversion but lowered CO2 selectivity. K2CO3 was gradually lost thus reducing the performance of the decorated hematite. In addition, hematite particles were sintered after adding K2CO3. CuO remarkably enhanced carbon conversion, reaction rate as well as CO2 selectivity, and the Cu-modified hematite remained stable and highly reactive although agglomeration occurred in CF-CLC cycles. Overall, CuO is superior to K2CO3 for modification of Carajás hematite, and the CuO-decorated hematite is suitable and promising OC for CF-CLC.

Optimization of Induration Cycle for Magnetite Concentrate and its Usage in Pellet-Making Process Designed for Hematite Concentrate

In the magnetite iron ore pelletization process, oxidation of magnetite followed by sintering of the oxidized magnetite (hematite) is desirable. Optimum preheating time & temperature and roasting time & temperature is required to get the desired properties of the pellets with magnetite, hematite, and hematite–magnetite blend. In order to utilize the magnetite resources in a current induration furnace, which is designed for hematite resources, detailed pelletization studies have been carried out to optimize the firing cycle for magnetite concentrate as well as magnetite with hematite concentrate. Under optimum conditions, such as preheating temperature 1000–1150 °C, preheating time 10 min, roasting temperature 1250 °C and roasting time 7.5 min, the cold compression strength (CCS) of magnetite roasted pellets was 325 kg/p, and this was due to recrystallization of secondary hematite particles, and development of the strong slag bond between primary and secondary hematite particles. The strength of hematite concentrate pellets was 260 kg/p. From laboratory studies, it was found that without disturbing the induration furnace firing cycle, which is designed for hematite ore ~5%, magnetite concentrate can be used along with hematite concentrate in pellet blend and the strength of the pellets was 270 kg/p. As the magnetite concentrate increases in the blend beyond 5%, the preheating zone residence time should be increased or a supply of extra oxygen is required. Laboratory as well as plant investigation has shown that the addition of magnetite to the hematite mix blend improved the strength of the pellets compared to hematite pellet alone.

Life cycle sustainability assessment of the nanoscale zero-valent iron synthesis process for application in contaminated site remediation.

Nanoscale zero-valent iron (nZVI) is the main nanomaterial used in environmental remediation processes. The present study aims to evaluate the life cycle sustainability of nZVI production methods applied in environmental remediation. Three production methods of nZVI were selected for analysis: milling, liquid reduction with sodium borohydride, and chemical reduction with hydrogen gas (in two approaches: considering the goethite and hematite synthesis and after using in nZVI production and, using goethite and hematite particles already synthesized for nZVI production). The life cycle sustainability assessment was carried out based on a multi-criteria and multi-attribute analysis. The multi-criteria analysis was used to determine impact category preferences of different specialists in sustainability and remediation, and calculate the sustainability score through a linear additive model. Finally, a Monte Carlo simulation was used to quantify the results uncertainty. The functional unit considered was 1.00kg of nZVI produced. The milling method and the hydrogen gas method in approach considering the use goethite and hematite particles already synthesized were the most sustainable. Moreover, the sustainability index was found to be influenced by the considered location scenarios as well as the perspectives of the different specialists, which was essential in producing a more accurate and comprehensive evaluation of the aforementioned sustainability methods. Overall, this study significantly contributed to applications of the state-of-the-art life cycle sustainability assessment in studies regarding nanomaterials, employing a simple methodology that included an analysis of different specialists. In addition, this is the first article that uses life cycle sustainability assessment in nanomaterials.

Synthesis of Magnetic Iron Oxide Nanoparticle from Logas Natural Sand and Its Application for the Catalytic Degradation of Methylene Blue

Structural properties, morphology, and the catalytic activity of hematite (α-Fe2O3) nanoparticles for degradation of methylene blue have been studied. For this purpose, the hematite particles were synthesised from Logas natural sand by 2 steps ball milling method. X-ray diffraction (XRD) confirmed the presence of a hematite (α-Fe2O3) phase. However, other phases such as SiO2 and FeTiO3 are also confirmed by XRD. Scanning electron microscopy (SEM) showed a wide distribution of particle sizes. Moreover, the shape of the grains is irregular form. The effect of reaction time and hematite nanoparticles dosage which affect the efficiency of catalytic reaction was investigated. Catalytic activity of hematite nanoparticles in the degradation of methylene blue (MB) was studied through ultraviolet visible spectroscopy (UV-Vis).

The formation of marine red beds and iron cycling on the Mesoproterozoic North China Platform

Abstract Marine red beds (MRBs) are common in sedimentary records, but their genesis and environmental implications remain controversial. Genetic models proposed for MRBs variably invoke diagenetic or primary enrichments of iron, with vastly different implications for the redox state of the contemporaneous water column. The Xiamaling Formation (ca. 1.4 Ga) in the North China Platform hosts MRBs that offer insights into the iron cycling and redox conditions during the Mesoproterozoic Era. In the Xiamaling MRBs, well-preserved, nanometer-sized flaky hematite particles are randomly dispersed in the clay (illite) matrix, within the pressure shadow of rigid detrital grains. The presence of hematite flake aggregates with multiple face-to-edge (“cardhouse”) contacts indicates that the hematite particles were deposited as loosely bound, primary iron oxyhydroxide flocs. No greenalite or other ferrous iron precursor minerals have been identified in the MRBs. Early diagenetic ankerite concretions hosted in the MRBs show non-zero I/(Ca+Mg) values and positive Ce anomalies (&amp;gt;1.3), suggesting active redox cycling of iodine and manganese and therefore the presence of molecular oxygen in the porewater and likely in the water column during their formation. These observations support the hypothesis that iron oxyhydroxide precipitation occurred in moderately oxygenated marine waters above storm wave base (likely &amp;lt;100 m). Continentally sourced iron reactivated through microbial dissimilatory iron reduction, and distal hydrothermal fluids may have supplied Fe(II) for the iron oxyhydroxide precipitation. The accumulation of the Xiamaling MRBs may imply a slight increase of seawater oxygenation and the existence of long-lasting adjacent ferruginous water mass.

High-Quality Inorganic Red Pigment Prepared by Aluminum Deposition on Biogenous Iron Oxide Sheaths.

Naturally occurring tubular iron oxides produced by aquatic bacteria in Leptothrix spp. are promising raw materials for hematite-based red pigments because of the higher heat resistance as compared with chemically synthesized hematite compounds. Here, we report iron oxide red pigments prepared through an additive deposition of aluminum on culture-based biogenous iron oxide (cBIOX) sheaths using an artificial culture system of L. cholodnii strain OUMS1. The heat-treated Al-containing cBIOXs exhibited elevated chroma and lightness along with increasing Al contents and enhanced thermal stability of color tones to repetitive heat treatments. XRD analysis showed a monophasic pattern of hematite in the Al-rich cBIOX after heating at a wide range of high temperatures. Micromorphology analyses revealed that putative Al oxide regions present among hematite particles plausibly prevented the grain growth of hematite during heat treatments. The results therefore demonstrate that the bioderived Al-rich iron oxide sheaths can serve as innovative inorganic red pigments feasible for industrial applications.

Synthesis of structure-controlled hematite nanoparticles by a surfactant-assisted hydrothermal method and property analysis

The impact of the type and concentration of surfactant on the synthesis of iron oxide nanoparticles (IONPs) has been investigated. Three types of surfactant — anionic, cationic, and nonionic surfactants (sodium dodecyl sulfate, SDS; cetyltrimethylammonium bromide, CTAB; and Triton X-100, respectively) — have been selected to control the phase, shape, and size of the IONPs. The synthesis was carried out with varying concentrations at 2, 4, and 6 times the critical micelle concentration (CMC) of each surfactant in a hydrothermal system at 180 °C. XRD and FE-SEM with the Microsoft Visio 2010 program have been applied for characterization and nanoparticle analysis. All synthesized IONPs, without and with the different surfactants, were characterized as spherical hematite with diameters in the range 15–205 nm, depending on the surfactant type and concentration. Surfactant type and concentration influenced the nature of the ferrous hexahydrate intermediate through acid-base equilibria and the Le Châtelier principle. The magnetic properties of the hematite nanoparticles have been examined by means of a vibrating sample magnetometer (VSM). The highest magneticity of synthesized hematite occurred at the transition from a single monolithic structure to one with multiple domains at a diameter of approximately 70 nm with a coercivity (Hc) of 225 Oe. The smallest hematite particles were chosen to prepare water-based nanofluids using the surfactants as stabilizing agents. Colloidal stability of the nanofluids has been studied by sedimentation, turbidity, and ζ-potential analyses. Nanofluid thermal conductivity has been determined by transient heat-transfer experiments. A nanofluid prepared in 2 CMC SDS solution showed the highest stabilization and a thermal conductivity of 0.4787 W/m.K.

Effect of particulate environment on the grinding kinetics of mixtures of minerals in ball mills

This paper presents the results of the experiments on the effect of particle size distribution and the volume ratio of components of the binary mixtures of calcite, hematite, and quartz on the grinding kinetics in ball mills. A total of forty-six grinding tests were carried out. These included forty-two dry grinding tests and four wet grinding tests. For each test, only one short-duration batch grinding experiment was carried out. The feed charge was prepared by pre-grinding the particulate material in the test ball mill. The results of these experiments have led to several important findings. Three of these findings are: (i) the size distribution of the ground product of the mixture of two minerals was practically the same as the mass-weighted sum of the size distributions of the ground product of these minerals when they were ground alone for the same duration, (ii) fine particles broke faster in the coarser environment, and (iii) while quartz fines were found to be most effective in increasing the specific breakage rate of coarse particles of quartz and hematite, in the case of calcite, hematite fines were found to be most effective. It shows that besides the hardness and density of the components, there are some other presently unknown properties that determine the fraction of the net energy input to the mill that is absorbed by the mixture.