Mark Pownceby

CSIRO, Mineral Resources, Senior Principal Research Scientist

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I joined CSIRO in 1992 as a Research Scientist. Prior to joining CSIRO I held a visiting research scientist position at the Bayerisches Geoinstitut, Germany, from 1989-1992. My research expertise is in the field of solid state chemistry and mineralogy. I apply this expertise in research projects related to: - ilmenite characterisation and processing, - the characterisation of iron ores and their sintered products, - the mineralogy of uranium ores, and - experimental phase equilibria.

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Papers by Mark Pownceby

Deportment of Metals from E-Waste PCBs towards Alloy and Slag Phases during Smelting Using CaO-Al2O3-SiO2-B2O3 Slags

Minerals, May 26, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more

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Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of MgO Source on Phase Formation during Heating

Isij International, Apr 15, 2022

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$Research paper thumbnail of Predicting iron ore sinter strength through partial least square regression (PLSR) analysis of X-ray diffraction patterns$

Predicting iron ore sinter strength through partial least square regression (PLSR) analysis of X-ray diffraction patterns

Powder Diffraction, Oct 26, 2017

The decrease in quality of Australian iron ore, coupled with the demand for more efficient energy... more The decrease in quality of Australian iron ore, coupled with the demand for more efficient energy use, means that closer monitoring and optimisation of process conditions for iron ore sinter production is required. Here, the suitability of using partial least-squares regression analysis of powder X-ray diffraction data, collected for iron ore sinter samples, for the prediction of iron ore sinter strength has been further assessed. In addition, a preliminary assessment of the effect of 2θ range on the quality of prediction has been made. For the purposes of process control, the level of correlation between predicted strength and actual sinter strength would inform an operator whether or not the process was operating within the acceptable limits, or whether there was a potential problem requiring further investigation or rapid intervention. Reducing the 2θ range was found to reduce the level of correlation between predicted and actual strength, to a point where the particular analysis may no longer be suitable for process control.

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Application of a Floatex density separator for iron recovery from Pilbara iron ore plant rejects

Mineral Processing and Extractive Metallurgy Review, Aug 28, 2022

How geochemistry maps upflow in the Ranger U mineral system: using this data for exploration

Effect of sintering conditions on the formation of mineral phases during iron ore sintering with New Zealand ironsand

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A comparative bio-oxidative leaching study of synthetic U-bearing minerals: Implications for mobility and retention

Journal of Hazardous Materials, Feb 1, 2021

In this study, the effects of bio-oxidative leaching on several synthetic uranium minerals-Uranin... more In this study, the effects of bio-oxidative leaching on several synthetic uranium minerals-Uraninite [UO 2 ], Pitchblende [U 3 O 8 ], Coffinite [USiO 4 ], Brannerite [UTi 2 O 6 ] and Betafite [(U,Ca) 2 (Ti,Nb,Ta) 2 O 7 ]) compared to chemical leaching in the presence of pyrite was investigated. In all cases, bio-oxidative leaching was faster and increased overall %U extraction compared to chemical leaching. The results indicated that the bio-oxidative leachability of the uranium minerals was in the order: pitchblende≈ uraninite > coffinite>> brannerite > betafite. The leaching of pitchblende and uraninite was fast and complete; U extraction from coffinite was slower over 28 days' during the bioleaching. The use of thermophiles doubled the recovery of U from refractory brannerite. The results highlight the significant capability of bio-leaching in the recovery of U from brannerite; both mesophilic and thermophilic bacteria was found to enhance U recovery likely through enhanced breakdown of the titanate structure. Brannerite is often found in significant quantities within ore tailings due to its refractory nature, which can lead to subsequent release of U into the environment. Conversely, betafite is highly stable in the presence of mesophile and moderate thermophiles, which suggested that betafite materials can be a viable future host for long term storage for spent nuclear fuels.

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Thermodynamic stability of SFCA (silico-ferrite of calcium and aluminum) and SFCA-I phases

Journal of the American Ceramic Society, Apr 20, 2017

Silico-ferrite of calcium and aluminum (SFCA) and SFCA-I phases form in iron ore sintering operat... more Silico-ferrite of calcium and aluminum (SFCA) and SFCA-I phases form in iron ore sintering operations. Their behavior in blast furnaces, with sinter being a significant component of blast furnace burden, is of critical importance to the ironmaking process. They have complex disordered crystal structures and form over a range of composition. In the present work, enthalpies of formation from oxides for five different SFCA compounds and one SFCA-I phase were measured by oxide melt solution calorimetry in molten lead borate solvent at 800°C. The

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Elaboration of alkali activated materials using a non-calcined red clay from phosphate mines amended with fly ash or slag: A structural study

Materials Chemistry and Physics, Dec 1, 2020

Abstract This study aims to explore the feasibility of using waste red clay from a sedimentary, i... more Abstract This study aims to explore the feasibility of using waste red clay from a sedimentary, interlayered phosphate deposit to produce a geopolymer mortar without any pre-treatment. Alkali activated mortars were prepared by mixing fly ash or slag with red clay and sand, using different fly ash or slag/red clay ratios. The effects of sodium silicate to sodium hydroxide ratio (SS/SH) and curing time on the mortar's properties were studied. The results showed that compared to fly ash-based alkali activated materials, an increase of the slag content resulted in the formation of dense mortars while in the case of fly ash based-samples more porous mortars were formed when the fly ash amount was increased. The mineralogical investigations indicated a partial contribution of montmorillonite and palygorskite from the clay to the alkali activation reaction. The mechanical properties of the materials were promising with a maximum compressive strength of up to 39 MPa obtained for the mixture of fly ash and red clay at a fly ash/red clay ratio of 2 and a SS/SH of 1.

The influence of ore composition on sinter phase mineralogy and strength

Mineral Processing and Extractive Metallurgy, Jul 2, 2016

The physical properties of iron ore sinter are largely influenced by raw material properties, in ... more The physical properties of iron ore sinter are largely influenced by raw material properties, in particular the bulk ore composition and its associated mineralogy. The levels of Fe, SiO 2 , Al 2 O 3 , MgO and other elements, together with the nature of the minerals in the fine ore and associated sintering conditions play a major role in determining the abundance and type of hightemperature bonding phases that form during sintering. This study using natural ores combines in situ X-ray diffraction experiments in model sinter systems with laboratory-based compact sinter tests to examine the links between iron ore composition and sintering conditions and their effects on sinter strength. Results help to establish the critical compositional and thermal parameters that control the bonding phase chemistry, which in turn influences the strength, a key sinter quality parameter of the sinter matrix.

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Chemical and microstructural characterisation studies on natural and heat treated brannerite samples

Minerals Engineering, Dec 1, 2012

Composition, structure, texture and gangue minerals associated with three naturally occurring ura... more Composition, structure, texture and gangue minerals associated with three naturally occurring uraninite samples (USG-Saxony, Germany; UPA-Palette mine, Australia and; UEA-El Sharana mine Australia) were investigated. The UEA sample contained ura ninite associated with uranyl oxide species, Pb-rich uranylphosphate and Pb/Al phosphate phase with trace levels of galena and sulphides. The UPA sample contained uraninite associated with meta-autunite, Pb/Al phosphate phase and other minor phases including carbonates, quartz, fluorapatite, gold and various Zn/Fe/Cu sulphides. The USG mineralogy was dominated by the sulphides sphalerite and galena with uraninite only a minor component along with unidentified Fe/Mg-rich aluminosilicate, muscovite, coffinite and other sulphides. All samples exhibited complex textural and chemical modifications compared to stoichiometric UO 2. The uraninites were substituted mainly by Ca and radiogenic Pb and were highly altered. Alteration was associated with significant variations in chemistry with unaltered uraninite in samples UPA and UEA typically being richer in U, Ca and Pb comp ared to altered regions. The altered uraninite also was more hydrated. Altered uraninite in sample USG had higher Fe, Pb, S and As compared to less altered uraninite and was significantly depleted in U and Ca. The high Pb in the uraninite was opposite to that observed in the UEA and UPA samples but may be related to the high abundance of galena in the sample. The compositional, textural and microstructural aspects of uraninite are likely to play an important role in any process to extract uranium from uraninite-containing ores.

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Effects of Sintering Materials and Gas Conditions on Formation of Silico-Ferrites of Calcium and Aluminium during Iron Ore Sintering

Isij International, 2016

Silico-ferrites of calcium and aluminium (SFCA) are desirable phases in a high quality iron ore s... more Silico-ferrites of calcium and aluminium (SFCA) are desirable phases in a high quality iron ore sinter product. The effects of sintering temperature, CaO/SiO 2 ratio, sintering gas atmosphere and cooling procedure on the phase composition of sintered specimens from an industrial sinter blend were examined with focus on the formation of SFCA phases. The proportions of mineral phases in specimens sintered at 1 250-1 325°C were quantitatively examined using image analysis. SFCA can be formed at low temperatures by solid state reactions, the formation of which was enhanced by increasing temperature. Further increasing sintering temperature promoted the reduction of Fe 3 + in the SFCA crystal structure to Fe 2 + and consequent decomposition of SFCA. At high temperatures, SFCA was produced during cooling via crystallisation from a silicate melt. Maintaining a high oxygen partial pressure favours the formation of SFCA, either via solid state reactions or from a melt. This is attributed to hematite being available as a reactant for SFCA formation. Similarly, increasing CaO/SiO 2 ratio provides more CaO as a reactant and promotes SFCA formation. KEY WORDS: sintering; iron ore; silico-ferrites of calcium and aluminium; phase composition.

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Upgrading a Brahmaputra River sand from northern Bangladesh by flotation to produce a high-grade silica glass sand concentrate

Mineral processing and extractive metallurgy, Feb 28, 2022

Experimental study into the beneficiation of a ferruginous rare earth bearing lateritic ore by magnetising roasting and magnetic separation

Minerals Engineering, Jun 1, 2019

The beneficiation of ferruginous rare earth bearing ores derived from lateritic deposits by conve... more The beneficiation of ferruginous rare earth bearing ores derived from lateritic deposits by conventional mineral dressing processes is usually difficult due to characteristics of these ores such as fine grain size, complex texture and similar physical characteristics between rare earth minerals and iron oxide gangue. The removal of iron oxides would offer significant advantages with respect to downstream rare earth mineral processing. The purpose of this study was to demonstrate at bench scale the feasibility of magnetically separating iron oxides from a ferruginous lateritic rare earth ore after the ore had been subjected to reduction roasting to convert feebly magnetic iron (III) oxides to magnetite. The effects of magnetic field strength and feed top size on the efficiency of low intensity magnetic separation (LIMS) was explored through rougher magnetic separation tests using a Davis tube tester and chemical and mineralogical analysis of the rougher magnetic concentrates and tails was performed. Magnetic separation was successful in removing iron (as magnetite) to the concentrate at a minimum field strength of 0.2 T; this was however non-selective, with significant amounts of rare earths reporting to the magnetic fraction. The rare earth enriched tails showed decreased grade and recovery and this was due to a number of factors including insufficient liberation, presence of iron oxide coatings on mineral surfaces and heteroflocculation. The findings of this study provided insight towards the potential optimisation and viability of the proposed process of magnetising roasting and low intensity magnetic separation as a means to beneficiate ferruginous lateritic rare earth ores.

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Effect of Temperature, Time, and Cooling Rate on the Mineralogy, Morphology, and Reducibility of Iron Ore Sinter Analogues

JOM, Nov 16, 2020

Analogue sinter tablets were produced at temperatures between 1250°C and 1320°C, with a range of ... more Analogue sinter tablets were produced at temperatures between 1250°C and 1320°C, with a range of hold times and cooling rates. Platy silico-ferrite of calcium and aluminum (SFCA) morphology was identified in samples produced at 1250°C using reflected light microscopy; however, quantitative x-ray diffraction (XRD) identified the presence of the SFCA phase, with no SFCA-I detected. This proves that the platy SFCA morphology common in analysis by reflected light microscopy cannot be attributed to the SFCA-I mineral without further analysis. Micro-XRD and electron probe micro-analysis (EPMA) were carried out on an area of platy SFCA confirming this result. The sinter analogue tablets were reduced in a 30% CO, 70% N 2 gas mixture at 900°C in a tube furnace thermo-gravimetric analyzer. The degree of reduction of the tablets in this study was found to be controlled by the porosity of the samples, rather than by the morphology or mineralogy of the bonding phase.

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Recovery and processing of zircon from Murray Basin mineral sand deposits

Mineral Processing and Extractive Metallurgy, Aug 31, 2015

Mineral sand deposits in the Murray Basin offer the potential for significantly expanding Austral... more Mineral sand deposits in the Murray Basin offer the potential for significantly expanding Australia's production of ilmenite, rutile and zircon. Since prices of zircon and rutile are higher than ilmenite, and zircon grades in most deposits are significantly higher than those for rutile, zircon often is the major economic mineral component in mineral sand deposits. Two types of deposits occur in the Murray Basin. They comprise strandline deposits, in which the particle size of the heavy minerals is similar to that in other Australian deposits, and fine grained, sheet-like, WIM style, deposits. While production from several strandline deposits has commenced, the fine grained deposits, which contain significantly greater amounts of mineralisation, are still to be developed. Problems with processing the finer particle size of the mineralisation, its variable mineralogy, higher surface and lattice impurity levels, in particular uranium and thorium in zircon grains, have contributed to this. Overcoming these problems is necessary to obtain the full commercial value from the Murray Basin deposits. Processing to recover a fine grained zircon concentrate from the extensive WIM style deposits and the removal of impurities in the concentrate are discussed in this paper. In particular, treatments to remove surface and lattice impurities, and to lower uranium and thorium levels by an acid leach and with heat and leach treatments, are reviewed. The conditions used in the heating treatment (e.g. temperature and nature of any fluxes added) affect the impurity removal and whether zirconia (ZrO2) or zircon (ZrSiO4) is obtained as the product.

Comparison of the chemistry and mineralogy of ilmenite concentrates sourced from fluvial (Brahmaputra River) and beach placer (Cox’s Bazar) deposits, Bangladesh

Ore Geology Reviews, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Effect of Addition of Mill Scale on Sintering of Iron Ores

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Jun 30, 2016

Iron-rich (65 to 70 pct total Fe) mill scale generated during processing by steel mills can be re... more Iron-rich (65 to 70 pct total Fe) mill scale generated during processing by steel mills can be recycled by using it as a ferrous raw material in the sintering process. The effect of mill scale addition on the phase formation of sintered specimens from an industrial sinter blend containing 0 to 15 wt pct mill scale was examined, and the mineral phases formed during sintering under various conditions (T = 1523 K to 1598 K [1250°C to 1325°C] and gas compositions of pO 2 = 0.5, 5 and 21 kPa) were quantitatively measured. For samples sintered in air (pO 2 = 21 kPa), there was negligible effect of mill scale addition on the phases formed. The oxidation of the mill scale was complete, and phases such as Silico-Ferrite of Calcium and Aluminum (SFCA), SFCA-I, and hematite dominated. Under lower oxygen partial pressures (pO 2 = 0.5 or 5 kPa), and throughout the temperature range examined, the mill scale was converted to magnetite, with the extent of reaction controlled by the hematite-magnetite conversion kinetics. When sintered in the gas mixture with pO 2 = 5 kPa, an increase in the mill scale content from 0 to 15 wt pct resulted in a decrease of hematite and total SFCA phases and a corresponding increase in the amount of magnetite which formed. The oxidation of wustite in mill scale to magnetite decreased the local partial pressure of O 2 and increased sintering temperature, which promoted the decomposition of hematite.

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Thermodynamic data from redox reactions at high temperatures. IV. Calibration of the Re-ReO2 oxygen buffer from EMF and NiO+Ni-Pd redox sensor measurements

Contributions to Mineralogy and Petrology, 1994

Divariant oxide plus metal assemblages potentially make useful redox sensors for use in hydrother... more Divariant oxide plus metal assemblages potentially make useful redox sensors for use in hydrothermal and other high pressure experiments. Here we report the calibration of the (Ni, Mn)O/Ni redox sensor in which the Ni/NiO (NNO) oxygen buffer is displaced to lower oxygen chemical potentials (gO2), by the solid solution of MnO in the oxide phase. This assemblage was chosen because: (1) it covers a useful range of gO2; (2) the system can be calibrated very accurately. Values of ~tO2 defined by the (Ni, Mn)O/Ni assemblage were determined electrochemically, from 900 to 1300 K, using calcia-stabilized zirconia solid electrolytes. The oxide compositions (8 in total, ranging from 0.1 < XN~o-< 0.8) were analysed afterwards by electron microprobe, and were checked for internal consistency by measuring the lattice parameters (ao), using powder XRD. The accuracies of the measurements, both assessed theoretically and established empirically, are (lcy): +80J/tool in ~tO2, _+0.0002A in ao and _+ 0.002 to 0.005 in XNio. Activity-composition relations were fitted to the Redlich-Kister formalism. There is a slight asymmetry (corresponding to a subregular model) across the solution with Ao ~ = 9577(_+45) J/mol, and A] =-477 (+80) J/tool. The experimental data were also used to derive the parameters Vex, H ex and Sex. There is no obvious relationship between excess volumes and enthalpies of mixing, nor between excess volumes and excess entropies. The experimental data from this study have been used to formulate the (Ni, Mn)O/Ni redox sensor expression;

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Signature of Himalayan orogenic features in Brahmaputra River sediments, Bangladesh: Evidence from single-grain heavy mineral chemistry

Chemie der Erde, Sep 1, 2022

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