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Dutwa is a nickel laterite atmospheric leach project in Tanzania under development by African Eagle Resources in 2012. A bankable feasibility study has been progressed to evaluate mining of the resource, 107 000 000 t at 0.92% Ni, followed by hydrometallurgical processing on-site to make a mixed Ni-Co intermediate product. The unique relatively high silica contents in the Dutwa deposits, as opposed to the limonite more commonly occurring in nickel laterites, presented the possibility for beneficiation of the ores to enhance the leach feed Ni grades and provide economic benefits in terms of operating and capital cost efficiencies. Geometallurgical relationships were developed from the results of an extensive variability metallurgical test-work programme for beneficiation and leaching, which improved understanding of ore classifications within the deposit and their responses. The geometallurgical information obtained has been instrumental in making key preliminary techno-economic decisions, such as forecasting whether or not mined material should be beneficiated, and was ultimately used to drive the mine plan towards the prioritisation of areas within the deposits that delivered the best cost efficiencies and overall project economic outcomes., Dutwa is a nickel laterite atmospheric leach project in Tanzania under development by African Eagle Resources in 2012. A bankable feasibility study has been progressed to evaluate mining of the resource, 107 000 000 t at 0.92% Ni, followed by hydrometallurgical processing on-site to make a mixed Ni-Co intermediate product. The unique relatively high silica contents in the Dutwa deposits, as opposed to the limonite more commonly occurring in nickel laterites, presented the possibility for beneficiation of the ores to enhance the leach feed Ni grades and provide economic benefits in terms of operating and capital cost efficiencies. Geometallurgical relationships were developed from the results of an extensive variability metallurgical test-work programme for beneficiation and leaching, which improved understanding of ore classifications within the deposit and their responses. The geometallurgical information obtained has been instrumental in making key preliminary techno-economic decisions, such as forecasting whether or not mined material should be beneficiated, and was ultimately used to drive the mine plan towards the prioritisation of areas within the deposits that delivered the best cost efficiencies and overall project economic outcomes.

The separation of iron ore in a prototype batch jig separator developed by Mintek in South Africa, referred to as the Mineral Density Separator (MDS), can separate ore samples into multiple bulk density fractions, provided that narrow feed size ranges are used. In this study, the performance of the equipment is considered by use of iron ore particles coloured according to density. This facilitated visualization of the density composition of the stratified ores. The highest density iron ore (>4000 kg/m3) could be separated efficiently from gangue material, but satisfactory stratification of lower density particles (<3600 kg/m3) could not be achieved.

The ability of junior companies to develop projects depends on selection of the right project team with all the appropriate skills, the characteristics of the orebody, the cost of development to the stage where funding can be achieved for the project, identifying the most cost-effective process flow sheet, the ability to source funding for the project, dealing with associated project risks and aligning project selection with the company strategy. By following established process development guidelines the risks associated with project selection and process development can be managed and maintained at an acceptable level, providing sufficient test work has been completed using samples generated along recognised guidelines and at an appropriate scale relevant to the size and value of the project. Guidelines that may help small mining companies in getting projects off the ground are presented. Strong selling of the project to the public should not be carried out before the initial resource definition and at least some test work has been completed, but once the public know about the project they should be kept informed to maintain interest in the company and the project. If the project appears to be even slightly marginal all aspects of the study should be conducted thoroughly as if it is not done perfectly there is every chance that something may go wrong. Significant focus should be given to financial modelling, ensuring that as many eventualities as possible have been considered and backup plans are in place to cover these eventualities. The right expertise should be involved for each stage and, if not internally available, should be contracted from reputable consulting companies. The reputation of the contractor must be applicable to the design at hand. Every aspect of the project should be peer reviewed by a suitable expert in the field. Larger consulting companies are often able to provide most, if not all, of the reviews from within a single company. The junior c, The ability of junior companies to develop projects depends on selection of the right project team with all the appropriate skills, the characteristics of the orebody, the cost of development to the stage where funding can be achieved for the project, identifying the most cost-effective process flow sheet, the ability to source funding for the project, dealing with associated project risks and aligning project selection with the company strategy. By following established process development guidelines the risks associated with project selection and process development can be managed and maintained at an acceptable level, providing sufficient test work has been completed using samples generated along recognised guidelines and at an appropriate scale relevant to the size and value of the project. Guidelines that may help small mining companies in getting projects off the ground are presented. Strong selling of the project to the public should not be carried out before the initial resource definition and at least some test work has been completed, but once the public know about the project they should be kept informed to maintain interest in the company and the project. If the project appears to be even slightly marginal all aspects of the study should be conducted thoroughly as if it is not done perfectly there is every chance that something may go wrong. Significant focus should be given to financial modelling, ensuring that as many eventualities as possible have been considered and backup plans are in place to cover these eventualities. The right expertise should be involved for each stage and, if not internally available, should be contracted from reputable consulting companies. The reputation of the contractor must be applicable to the design at hand. Every aspect of the project should be peer reviewed by a suitable expert in the field. Larger consulting companies are often able to provide most, if not all, of the reviews from within a single company. The junior c

The effect correct mineralogical information has on the subsequent metallurgical test-work programme and process selection is discussed using a case study. Factors such as type of rock, rainfall and topography influence the minerals that ultimately form in various orebodies, with the result that different orebodies often react differently during metallurgical test-work programmes. It is therefore important to obtain accurate mineralogical and elemental deportment data, which will also indicate where the valuable metal-containing minerals are located within the orebody. The better a metallurgical test-work programme is planned and executed during the early phases, the more accurate the decision-making process will be during the selection phase. Improved integration between geological and metallurgical data-gathering (geometallurgy) during early phases will result in more accurate predictions with regard to throughput and recovery during modelling and process. Equipment selection will be considerably simpler in later phases with early planning, with improved mine and process scheduling and subsequent net present value (NPV)., The effect correct mineralogical information has on the subsequent metallurgical test-work programme and process selection is discussed using a case study. Factors such as type of rock, rainfall and topography influence the minerals that ultimately form in various orebodies, with the result that different orebodies often react differently during metallurgical test-work programmes. It is therefore important to obtain accurate mineralogical and elemental deportment data, which will also indicate where the valuable metal-containing minerals are located within the orebody. The better a metallurgical test-work programme is planned and executed during the early phases, the more accurate the decision-making process will be during the selection phase. Improved integration between geological and metallurgical data-gathering (geometallurgy) during early phases will result in more accurate predictions with regard to throughput and recovery during modelling and process. Equipment selection will be considerably simpler in later phases with early planning, with improved mine and process scheduling and subsequent net present value (NPV).

Laboratory and pilot scale tests were carried out on the remediation of material from the East Paydam tailings dam in the Vaal River region of South Africa's North West Province. As well as tailings from the gold operations, the material included crud from the associated uranium solvent extraction plant. The contaminated material was treated by soil washing and bioremediation. The results of the testwork are given, using sulphuric acid, acetic acid, oxalic acid and ethylene diamine acetic acid as leachants. These showed that the leaching of the heavy metals Mn, Ni and Zn was largely dependent on pH, and that extraction was raised by increasing the soil porosity and the use of bioremediation., Laboratory and pilot scale tests were carried out on the remediation of material from the East Paydam tailings dam in the Vaal River region of South Africa's North West Province. As well as tailings from the gold operations, the material included crud from the associated uranium solvent extraction plant. The contaminated material was treated by soil washing and bioremediation. The results of the testwork are given, using sulphuric acid, acetic acid, oxalic acid and ethylene diamine acetic acid as leachants. These showed that the leaching of the heavy metals Mn, Ni and Zn was largely dependent on pH, and that extraction was raised by increasing the soil porosity and the use of bioremediation.

The presence of Ca and Mg in the hydrometallurgical processing of base metals can result in contamination of the final product, high energy consumption and large bleed streams during electrowinning. A batch precipitation reactor was used to investigate the effects of the quantity of fluoride, Ca:Mg molar ratio, use of HF or NH4F as fluoride source and temperature on the precipitation of Ca and Mg. The results showed the possibility of controlling Ca and Mg through the precipitation of their fluorides without the co-precipitation of Ni and Co. At Mg:Ca molar ratios above 3 the precipitation of Mg was dominant. For a 10% stoichiometric excess amount of fluoride, 96.5% of the Ca and 98.5% of the Mg were removed. The use of NH4F resulted in higher Ca and Mg precipitation than HF, while temperature had a negligible effect., The presence of Ca and Mg in the hydrometallurgical processing of base metals can result in contamination of the final product, high energy consumption and large bleed streams during electrowinning. A batch precipitation reactor was used to investigate the effects of the quantity of fluoride, Ca:Mg molar ratio, use of HF or NH4F as fluoride source and temperature on the precipitation of Ca and Mg. The results showed the possibility of controlling Ca and Mg through the precipitation of their fluorides without the co-precipitation of Ni and Co. At Mg:Ca molar ratios above 3 the precipitation of Mg was dominant. For a 10% stoichiometric excess amount of fluoride, 96.5% of the Ca and 98.5% of the Mg were removed. The use of NH4F resulted in higher Ca and Mg precipitation than HF, while temperature had a negligible effect.

The difficulty is discussed of achieving dissolution rates higher than 90% under the normal operating conditions employed for the acid leaching of South African ores. Mineralogy and leachability studies were carried out on three different ore samples from the Vaal River area which averages 0.3 kg U308/t. The results indicate that optimum recoveries are not achieved due to the intrinsic inertness of the mineral brannerite, and that more extreme conditions such as pressure leaching may be required. The real value of U leaching may lie in the unlocking of extra Au (0.4-0.6 g/t) by the U leaching process which typically precedes cyanide leaching of Au., The difficulty is discussed of achieving dissolution rates higher than 90% under the normal operating conditions employed for the acid leaching of South African ores. Mineralogy and leachability studies were carried out on three different ore samples from the Vaal River area which averages 0.3 kg U308/t. The results indicate that optimum recoveries are not achieved due to the intrinsic inertness of the mineral brannerite, and that more extreme conditions such as pressure leaching may be required. The real value of U leaching may lie in the unlocking of extra Au (0.4-0.6 g/t) by the U leaching process which typically precedes cyanide leaching of Au.