The Bushveld Igneous Complex (BIC) in South Africa holds approximately three quarters of the world’s viable chromite ore deposits. Most chromite is used for the production of ferrochromium (FeCr), which is a relatively crude alloy. Several chromite seams exist in the BIC. The most economically viable seams are the lower group 6 (LG6), the middle group 1 and 2 (MG1 and 2) and the upper group 2 (UG2) seams. The LG and MG seams are exploited specifically for their chromium content, whereas the UG2 seam is mainly exploited for platinum group minerals (PGM). However, the upgraded UG2 chromite in the PGM tailing is increasingly being used as a feedstock for FeCr production. Many different process variations exist for FeCr production. However, the process option applied in most green and brown field FeCr expansion projects during the last two decades in South Africa has been the oxidative sintered process (also referred to as the Outotec or Outokumpu process). Notwithstanding the common application of the oxidative sintered pelletised feed technology in the South African FeCr industry, and the increased utilisation of beneficiated UG2 ore, a direct comparison of the physical properties of oxidative sintered pellets produced from UG2 with the physical properties of that produced with conventional metallurgical grade chromite ore is currently lacking in the peer-reviewed scientific literature. Therefore, the physical properties of oxidative sintered pellets produced from a typical beneficiated South African UG2 ore were compared with the physical properties of that produced with conventional South African metallurgical grade chromite ore in this study. The results indicated that the case study metallurgical grade chromite ore required 13 kWh/t more energy to mill than the case study UG2 ore prior to pelletisation, which can lead to substantial cost savings. The compressive strength of the oxidative sintered pellets of both case study ores statistically showed that oxidative sintered pellets made from UG2 ore Abstract were the same or better than those prepared from metallurgical grade chromite ore. A comparison of the abrasion strengths of the oxidative sintered pellets of both case study ores indicated that the pellets prepared from UG2 ore were superior compared to the metallurgical grade pellets. The reasons for the superior UG2 pellet strength were investigated with backscatter-, secondary electron- and elemental X-ray mapping scanning electron microscopy (SEM), which indicated that differences in crystalline structures at least partially contributed to the differences observed. Results presented here can be utilised by FeCr producers to better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr production. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

The Bushveld Igneous Complex (BIC) in South Africa holds approximately three quarters of the world’s viable chromite ore deposits. Most chromite is used for the production of ferrochromium (FeCr), which is a relatively crude alloy. Several chromite seams exist in the BIC. The most economically viable seams are the lower group 6 (LG6), the middle group 1 and 2 (MG1 and 2) and the upper group 2 (UG2) seams. The LG and MG seams are exploited specifically for their chromium content, whereas the UG2 seam is mainly exploited for platinum group minerals (PGM). However, the upgraded UG2 chromite in the PGM tailing is increasingly being used as a feedstock for FeCr production. Many different process variations exist for FeCr production. However, the process option applied in most green and brown field FeCr expansion projects during the last two decades in South Africa has been the oxidative sintered process (also referred to as the Outotec or Outokumpu process). Notwithstanding the common application of the oxidative sintered pelletised feed technology in the South African FeCr industry, and the increased utilisation of beneficiated UG2 ore, a direct comparison of the physical properties of oxidative sintered pellets produced from UG2 with the physical properties of that produced with conventional metallurgical grade chromite ore is currently lacking in the peer-reviewed scientific literature. Therefore, the physical properties of oxidative sintered pellets produced from a typical beneficiated South African UG2 ore were compared with the physical properties of that produced with conventional South African metallurgical grade chromite ore in this study. The results indicated that the case study metallurgical grade chromite ore required 13 kWh/t more energy to mill than the case study UG2 ore prior to pelletisation, which can lead to substantial cost savings. The compressive strength of the oxidative sintered pellets of both case study ores statistically showed that oxidative sintered pellets made from UG2 ore Abstract were the same or better than those prepared from metallurgical grade chromite ore. A comparison of the abrasion strengths of the oxidative sintered pellets of both case study ores indicated that the pellets prepared from UG2 ore were superior compared to the metallurgical grade pellets. The reasons for the superior UG2 pellet strength were investigated with backscatter-, secondary electron- and elemental X-ray mapping scanning electron microscopy (SEM), which indicated that differences in crystalline structures at least partially contributed to the differences observed. Results presented here can be utilised by FeCr producers to better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr production. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The Bushveld Complex of South Africa contains three of the most important platinum deposits in the world namely the Merensky Reef, the Upper Group Two (UG2) chromitite reef and the Platreef. These three ore bodies are principally beneficiated by froth flotation. During the beneficiation of chromite hosted PGE’s by froth flotation, chromite represents the principal gangue mineral. This is particularly true for the UG2 main seam. An excess of more than 3% in mass of chromite in the PGM concentrate is known to result in significant problems in the downstream processing and extraction of PGEs. The variability in texture and composition of chromite due to its primary crystallization and subsequent modification by the development of potholes or through IRUP intrusions are thought to influence the flotation behaviour of the UG2 main seam chromitite ore. This study conducted at Waterval Mine investigated the role of mineralogical characteristics of chromites on the flotation performance of three different environments for the UG2 main seam: (1) “normal” UG2 main seam; (2) UG2 main seam affected by pothole formation; and (3) UG2 main seam affected by IRUP intrusion. This was achieved through an extensive petrographic investigation of the chromites from each environment, to individually characterise their primary textures. This was followed by compositional characterisation of the chromite from each environment. Finally the flotation performance of the ore from each environment was investigated, using small scale batch flotation experiments, to establish any linkage between the textures, the composition and the flotation performance of the chromite from different environments. In this study it was found that the UG2 normal reef and the UG2 reef affected by pothole formation are both principally characterised by primary mineralogical features comprising mainly fine‐grained chromite as the cumulate phase and orthopyroxene and plagioclase as intercumulate phases. These two reef types were also found to be identical in the composition of the chromites present. In addition, in both of these almost unaltered reef types it was found that chromite showed small recoveries by flotation. On the other hand, it was found that the UG2 affected by IRUP intrusion was affected by post‐magmatic alteration that had overprinted primary textures and compositional features. This resulted in the replacement of primary minerals by secondary alteration assemblages. Orthopyroxene was iii replaced by serpentine, chlorite, amphibole and talc, while plagioclase is replaced by sericitic alteration. Furthermore, this alteration also resulted in modification of the chromite compositions. The compositional change in the chromites from the IRUP reef type resulted in Fe and Ti enrichment of chromite with increasing magnetic properties, and Cr, Al and Mg depletion. The alteration also resulted in the coarsening of chromite in the IRUP affected main seam reef particularly at the bottom and the top of the main seam. These compositional and textural modifications, principally the post‐magmatic alteration of intercumulate orthopyroxene, resulted in a greater recovery of chromite by flotation in the concentrate from the IRUP affected ore compared to the two other two ore types where there was small amount of chromite recovered. The characterisation of the recovered chromite revealed that the principal reason for chromite flotation was caused by the mineral association of chromite with hydrophobic Si, Mg, Fe rich phases, principally altered orthopyroxene and associated serpentine, chlorite, amphibole and talc. This investigation showed that the difference in mineralogical and flotation performances of chromite from the different UG2 main seam reef types was caused by the postcrystallisation alteration of cumulate and intercumulate phases due to the emplacement of IRUPs. Although IRUP affected UG2 main seam ore is not currently processed, it could be processed much more rapidly than the other two types of UG2 main seam ores because of its softer character resulting in shorter milling times. This is most likely a function of the presence of alteration phases and the presence of coarser chromite grains, as well as already brecciated chromite grains. Savings associated with the shorter milling time of this ore type are perhaps offset by the cost of the higher dosages of depressant required to suppress the floatable chromite in this ore type. However, given the energy cost of longer milling times, the cost of the depressant is likely to be insignificant. Moreover, the processing of the UG2 main seam ore affected by IRUP intrusion would also require a different approach to extraction of the ore to keep it separate from the normal reef ore.

The Twickenham Platinum Mine (TPM) Project is located in the north eastern limb of the Bushveld Complex, north west of Steelpoort in the Limpopo Province. The property hosts platinum group metals (PGM) mineralisation in the Merensky Reef (MR) and Upper Group 2 Chromitite (UG2). The two reefs are separated by 400 m of mafic and ultramafic rocks of the Rustenburg Layered Suite. The question that must be answered with this study relates to the economic viability of the MR compared to that of the UG2 at the TPM Project, as it stands in 2011. The assumption is that no mining has commenced on this project and that there is an equal opportunity to commence mining on one of the reefs. The study describes the ore body characteristic for each reef, focussing on the lithologies, structure, and resources available. The discounted cash flow (DCF) method was used to determine the economic value of each reef. The net present value (NPV) and internal rate of return (IRR) were calculated and used to compare the ore bodies. The input parameters to the DCF are the main limiting factors to this method, as the results are heavily dependent on the assumptions made. The input parameters used were based on actual published values and generally accepted and motivated assumptions. A sensitivity and risk analysis was completed to identify value ranges and potential risks to the projects. The outcome of the analysis has been compared to other projects as a benchmark to ensure the project assumptions were realistic. The world markets supply and demand for PGM is intricately related to exchange rates, metal prices, inflation, and investment risk. These have an influence on the strategic planning for a company as well as investment decisions through various project evaluation methods. South Africa has a long history of mining and metals extraction. Extensive mining legislation has been developed to ensure the country’s mineral wealth is protected and the health and safety of employees are high priority. Specific challenges related L! to mining on the Eastern Limb are discussed in order to justify the high risk assigned to the project for this evaluation. The DCF was calculated and the outcome indicated that neither the MR nor the UG2 is economically viable using these parameters in the 2011 economy. The MR evaluation produced a negative NPV (R -1,664,541,443.47) and an IRR of 9 %, which is well below the required discount rate of 12 %. The initial project capital will be repaid after 19 years of the 33 year life of mine. The sensitivity analysis showed that by reducing the initial capital by 30 %, the project produces a positive NPV. The other factor that produced a positive NPV was by reducing the operating cost by 50 %. This project will have to be re-evaluated after all parameters have been tested and some re-engineering has been done to optimise the extraction of the MR ore body. The UG2 evaluation produced a negative NPV (R -109,614,208.27) and an IRR of 12 %, equal to the required discount rate. The initial project capital will be repaid after 16 years of the 32 year life of mine. The sensitivity analysis showed encouraging results, as minor changes to the input parameters produced a positive NPV. The two parameters that were most significant were the recoveries and the capital requirements. By increasing the recovery percentage by 2 %, the project NPV becomes positive and a reduction of the initial capital by 10 %, also resulted in the NPV becoming positive. This indicates that with some refinement to the input parameters, the UG2 could be extracted as an economically viable project. The only concern is the sensitivity to changes in grade, which will have to be very well defined and controlled when mining commences. The risk assessment related closely to the challenges identified for a mining operation on the Eastern Limb, with the relationship with the local community and the build-up phase of the project emerging as the highest risks. The limited infrastructure development and high levels of poverty that exists in the area has a direct influence on the support structures and services available for the build-up phase of a mine. The build-up phase requires substantial development and services that will have to be sourced at high risk and cost from substantial distances, to ensure that steady state is reached. The socio-economic development of the local community is critical for the success of the mine. Upliftment of the local community in terms of education and training, job opportunities and health care will provide the foundation for a good relationship / Dissertation (MSc)--University of Pretoria, 2012. / Geology / Unrestricted