Rock Characteristics and Ball Mill Energy Requirements at Goldfields Ghana Limited, Tarkwa Gold Mine (TGM)


  • Charles Ebenezer Abbey University of Mines and Technology
  • Kenneth Joseph Bansah Missouri University of Science and Technology
  • Greg Galecki Missouri University of Mines and Technology
  • Kofi Agyeman Boateng University of Mines and Technology


Work index, Power draw, Computer simulation


Mineral processing plants often experience changes in throughput; blending patterns, and rock properties. These changes can have great impact on milling operations. As mining progresses, new deposits are discovered, which may have different characteristics from the designed plant parameters, a situation requiring re-assessment of the plant operating parameters. Goldfields Ghana Limited, Tarkwa Gold Mine (TGM), processes ores which occur in conglomerate reefs. The competence of the ore was observed to increase with increasing mining depth. Other rock properties such as porosity, micro-cracks and gold dissolution were also observed to change with depth. It therefore became necessary to conduct a study to ascertain the effect of changes in rock characteristics on the performance of the existing ball mill. The study characterized the mineralogy and rock characteristics of the ores being mined from three pits and the results were compared with design parameters. The parameters examined had deviated from the design; Work Index (WI) for example was lower than design and required simulation and adjustment. Samples taken at the same depth from each of the pits showed that Akontasi Pit has the most competent ores, followed by Kottraverchi Pit and then Teberebie Pit. Furthermore, throughput was the most sensitive variable and easiest to manipulate to achieve the energy draw required. Simulations showed that a plant throughput of about 1665 t/hr, instead of the current value of 1500 t/hr would be most suitable as an energy draw solution.

Author Biographies

Charles Ebenezer Abbey, University of Mines and Technology

Charles Ebenezer Abbey is a lecturer at the Minerals Engineering Department of the University of Mines and Technology. He has a Master of Philosophy Degree in Minerals Engineering. His research interests are in Environmental Remediation. Small Scale Process Innovations and Mineral Processing. Charles has been lecturing at UMaT since August 2010 and is a PhD candidate at UMaT. Charles has been the CEO of ACE Mineral Resources Consults since 2007 consulting in small scale mining and an active team member of Process Innovations. Charles has been involved in several high profile research jobs including The Government of Ghana, European Union Sponsored Mercury Abatement Project, Goldfields Ghana Limited CIL Plant Audit and HPGR Optimization Testworks

Kenneth Joseph Bansah, Missouri University of Science and Technology

Kenneth J. Bansah is a Teaching Fellow and PhD candidate at Missouri University of Science and Technology, Missouri, USA. He holds an MPhil Degree in Mining Eng. from UMaT, Ghana (2009) and BSc. (First Class) in Mining Engineering from the Kwame Nkrumah University of Science and Technology, Ghana (2006). He has significant industry experience as a Mining Engineer with Taysec Construction Ltd., AngloGold Ashanti, and Goldfields Ghana Ltd. Since July 2010, Kenneth has been the Director and Chief Consultant of Safety & Environmental Research Consultancy Limited rendering consulting services in environmental and safety issues. His current research areas include blast optimization, comminution efficiency, finite element analysis, fracture mechanics, multichannel analysis of surface waves, operations research, safety and environmental management.

Greg Galecki, Missouri University of Mines and Technology

Dr. Greg Galecki is an Associate Professor of Mining Engineering at the Missouri University of Science & Technology, USA. He obtained his MSc. and PhD degrees in Mechanical Engineering at Wroclaw Technical University in Poland. He has over 30 years of experience in experimental waterjet use and designing special high pressure equipment.

He has successfully demonstrated coal comminution to submicron sizes for coal conversion into fuels. and has been involved in borehole mining for uranium and diamond.

His research interests are manufacturing and mineral processing. He has published over 60 articles including a book chapter. He has 27 inventions in waterjet technology and mining applications, 3 patents, and is internationally recognized as a scientific paper reviewer and waterjet expert.

Kofi Agyeman Boateng, University of Mines and Technology

Kofi Agyeman Boateng is a Master of Science in Minerals Engineering degree holder from the University of Mines and Technology, in Tarkwa, Ghana. He completed a diploma in Mechanical Eng.KNUST School of Mines and worked in Bonte for a few years. He has vast experience working in industry having worked in various capacities including Engineering Manager at Goldfields Ghana Limited Tarkwa Mine CIL Plant and a few other mines in other parts of Africa. Kofi loves Mineral Processing Research with emphasis on Comminution and donated a standard Bond Ball Test Mill to UMaT’s Minerals Engineering Department.


Anon. (1981), “Rock Characterization Testing and Monitoringâ€; ISRM Suggested Methods (Brown, E. T. ED)â€, Pergamon Press, Oxford, UK, pp. 84-85.

Barbery, G. (1991) “Mineral Liberation Measurement, Simulation and Practical Use in Mineral Processing Iâ€, GR Quebec.

Comeau, W. (1996), “Explosive Energy Partitioning and Fragment Size Measurement – Importance of Correct Evaluation of Fines in Blasted Rockâ€, Proc. of the Fragblast-5 Workshop on Measurement of Blast Fragmentation, Montreal,Canada,pp. 237-240.

Eloranta, J. W. (1995), “The Effect of Fragmentation on Downstream Processing Costsâ€, Proceedings of Explo’95 Conference, Brisbane, Qld, Australia, pp. 25-28.

Eloranta, J. W. (1997), “The Efficiency of Blasting versus Crushing and Grindingâ€, Proceedings of the 23rd Annual Conference on Explosives and Blasting Technique, International Society of Explosives Engineers, pp. 157-163.

Forbah Jnr, J. Y. and Amankwah, R. K. (2010), “Effects of Rock Fragmentation on Communition – A Case Study at Damang Gold Mineâ€, Presented at the 1st UMaT International Mining and Mineral Conference, Tarkwa, Ghana.

Fuerstenau, M. C., Chi, G., and Bradt, R. C. (1995), “Optimization of Energy Utilization and Production Costs in Mining and Ore Preparationâ€, XIX International Mineral Processing Congress, San Francisco, California, pp. 161-164.

Higgins, M. (1998), “JKSimBlast – Blast Simulation and Managementâ€, Presented at Blasting Analysis International Eighth High-Tech Seminar, Nashville, Tennessee, pp. 1-9.

Kanchibotla, S.S. (2000), “Mine to Mill Blasting to Maximise the Profitability of Mineral Industry Operationsâ€, Proc. 27th ISEE Conf., Anaheim, USA.

Kesse, G. O. (1985), “The Mineral and Rock Resources of Ghana†A. A. Balkema, Rotterdam, Holland.

Levin, J. (1992), “Indicators of Grindability and Grinding Efficiencyâ€, J. S. Afr. Inst. Min. Metall.,Vol. 92, No. 10, pp. 283-289.

Napier-Munn, T.J., Morrell, S., Morrison, R.D., Kojovic, T. (1999), “Mineral Communition Circuits – Their Operation and Optimisationâ€, Julius Kruttschnitt Mineral Research Centre, Isles Road, Indooroopilly, Queensland 4068, Australia, pp. 413.

Siddall, B., Henderson, G., and Putland, B. (1996), “Factors Influencing Sizing of SAG Mills from Drill Core Samplesâ€, Proc. Conf. International AG and SAG Grinding Technology, UBC, Vancouver, Canada, Vol. 2, pp. 463.

Simkus, R., and Dance A. (1998), “Tracking Hardness and Size: Measuring and Monitoring ROM Ore Properties at Highland Valley Copperâ€, Proc. Mine to Mill Conf., Brisbane, Australia.

Wills, B.A., and Atkinson, K. (1993), “Some Observations on the Fracture and Liberation of Mineral Assembliesâ€, Minerals Eng., pp. 697.






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