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Home , Dump leaching, Extractive metallurgy

THE EXTRACTIVE OF IN SOUTH AFRICA

VOLUME 2 SAIMM PUBLICATIONS

THE MONOGRAPH SERIES

M1 Lognormal-De Wijsian Geostatistics for Evaluation (2nd ed 1981) D.G. Krige M2 An Introduction to Geostatistical Methods of Mineral Evaluation (2nd ed 1981) J.-M.M. Rendu M3 Principles of Flotation (1982) Edited by R.P. King M4 Increased Underground Extraction of Coal (1982) Edited by c.J. Fauconnier and R.W.O. Kersten MS Rock Mechanics in Practice (1983) (3rd imp. 1986) Edited by S. Budavari M6 Assay and Analytical Practice in the South African Mining (1986) W.C. Lenahan and R. de L. Murray-Smith M7 The of Gold in South Africa, 2 volumes (1987) Edited by G. G Stanley

THE SPECIAL PUBLICATIONS SERIES

SP1 Proceedings, Underground Transport Symposium (1986) Edited by R.C.R. Edgar SAIMM PUBLICATIONS

THE SYMPOSIUM SERlIES

SI Mathematical Statistics and Computer Applications in Ore Valuation (1966) S2 Planning Open Pit Mines (1970) (4th imp.) Edited by P.W.J. van Rensburg S3 Application of Computer Methods in the Mineral Industry (APCOM 1973) Edited by M.D.G. Salamon S4 Infacon 1974 Edited by H. W. Glen SS Proceedings of the 12th CMMI Congress, 2 volumes (1982) Edited by H. W. Glen S6 Rockbursts and Seismicity in Mines (1984) Edited by N.C. Gay and E.H. Wainwright S7 The Planning and Operation of Open Pit and Strip Mines (1986) Edited by J.P. Deetlefs S8 GOLD 100: Proceedings of the International Conference on Gold (1986) Volume 1: Gold Mining Technology Edited by H. Wagner and R.P. King Volume 2: Extractive Metallurgy of Gold Edited by e.E. Fivaz and R.P. King Volume 3: Industrial Uses of Gold Edited by G. Gafner and R.P. King S9 APCOM 87: Proceedings of the Twentieth International Symposium on the Application of Computers and Mathematics in the Mineral Industries (1987) Volume 1: Mining Edited by L. Wade, R.W.O. Kersten and J.R. Cutland Volume 2: Metallurgy Edited by R.P. King and LJ. Barker Volume 3: Geostatistics Edited by Le. Lemmer, H. Schaum and F.A.G.M. Cami­ sani-Calzolari

The South African Institute of Mining and Metallurgy Monograph Series M7 The Extractive f 1 in S

Edited by G. G. Stanley

VOLUME 2

This book was commissioned by the Sub-Committee of Consulting Metallurgists of the Chamber of Mines of South Africa

Johannesburg 1987 Published by The South African Institute of Mining and Metallurgy Kelvin House, 2 Hollard Street, Johannesburg, 2001

©The Chamber of Mines of South Africa, 1987 P.O. Box 809, Johannesburg, 2000

ISBN 0 620 10944 0 Volume 2 o 620 10109 1 Volume 1 o 620 10945 9 The Set

Typeset by Scientific and Technical Typesetting Kelvin House, 2 Hollard Street, Johannesburg 2001

Printed in the Republic of South Africa by National Book Printers, Goodwood Outline of Contents

VOLUME 1

page Preface ...... XXXI Acknowledgements ...... xxxiii Foreword by President, Chamber of Mines of South Africa ...... xxxvii

Chapter 1 Geology and Mineralogy of the Principal Goldfields in South Africa ...... 1 Chapter 2 Sorting and Crushing ...... 69 Chapter 3 Milling and Classification ...... 121 Chapter 4 Gravity Concentration ...... 219 Chapter 5 Flotation ...... 235 Chapter 6 Cyanidation ...... 277 Chapter 7 Recovery of Gold from Solution by Cementation .. 331 Chapter 8 of Gold ...... 345 Chapter 9 Application of Activated Carbon to Gold Recovery 379

VOLUME 2

Chapter 10 of Gold at the Rand Refinery ...... 615 Chapter 11 Disposal of Residues ...... 655 Chapter 12 Retreatment of Residues and Waste Rock ...... 707 Chapter 13 Process Evaluation ...... 745 Chapter 14 Process Control ...... 793 Chapter 15 The Chemistry of the Extraction of Gold ...... 831 Chapter 16 Plant Design and Commissioning ...... 907 Chapter 17 Loss Control and Safety Management ...... 971 Chapter 18 Laboratories and Pilot Plants ...... 1013

Tables and Formulae ...... 1053

Index ...... 1073

vu Contents

VOLUME 2

page Chapter 10 Refining of Gold at the Rand Refinery, by K.G. Fisher ...... 615 10.1 Introduction ...... 615 10.2 Historical Development ...... 615 10.3 Function ...... 616 10.4 Metallurgical Operations ...... 618 10.4.1 Summary description ...... 618 10.4.2 Gold Refining Branch ...... 618 10.4.2.1 Flow sheet 618; 10.4.2.2 Melting and sampling 619; 10.4.2.3 Refining 621; 10.4.2.4 De-golding 626; 10.4.2.5 Electrolytic gold re- fining 626; 10.4.2.6 Fume recovery and sweep treatment 628 10.4.3 Refining Branch ...... 630 10.4.3.1 Flow sheet 630; 10.4.3.2 and reduction 630; 10.4.3.3 Electrolytic silver refining 633 10.4.4 Coin blank production ...... 637 10.4.4.1 Historical 637; 10.4.4.2 Process de­ scription 638 10.4.5 Smelter ...... 641 10.4.5.1 Flow sheet 641; 10.4.5.2 Sampling 641; 10.4.5.3 Blending and sintering 643; 10.4.5.4 Blast furnace 644; 10.4.5.5 648; 10.4.5.6 Pan furnace smelting 649; 10.4.5.7 Fume collection 651 10.4.6 Assaying and chemical analysis...... 652 10.5 Future Developments...... 652 10.6 References ...... 653

Chapter 11 Disposal of Residues, by G.1. MacPhail and J.C. Wagner ...... 655 11.1 Aim and Scope ...... 655 11.2 Planning...... 656

ix CONTENTS

11.2.1 Components of a residue disposal system ...... 656 11.2.2 Sizing ...... 657 11.2.2.1 Depositional area requirements 657; 11.2.2.2 Allowances for services 659; 11.2.2.3 Return water system 660; 11.2.2.4 Total area 660 11.2.3 Site selection ...... 660 11.2.4 Site exploration ...... 663 11.2.5 Pollution control considerations...... 665 11.3 Statutory Requirements...... 665 11.3.1 Legal considerations ...... 665 11.3.1.1 The Water Act 665; 11.3 .1.2 The Mines and Works Act 666 11.3.2 Licensing ...... 666 11.3.3 Environmental impact assessment ...... 666 11.3.3.1 Methods of assessment 667; 11.3.3.2 Remedial measures 667; 11.3.3.3 Monitoring 667 11.4 Design, Specification and Construction ...... 668 11.4.1 Operation...... 668 11.4.1.1 General 668; 11.4.1.2 Method of for­ mation of dam 669 11.4.2 Tailings delivery ...... 675 11.4.2.1 Pulp concentration 675; 11.4.2.2 Pumping and piping systems 676; 11.4.2.3 Pump and pipeline design 678; 11.4.2.4 Tailings distri- bution 678 11.4.3 Return water management ...... 678 11.4.4 Stormwater management ...... 683 11.4.4.1 General 683; 11.4.4.2 Top surface of dam 684; 11.4.4.3 Side slopes 684 11.4.5 Slope stability ...... 685 11.4.5.1 Influence of foundation soils 685; 11.4.5.2 Influence of tailings product 685; 11.4.5.3 Influence of rate of rise 687; 11.4.5.4 Influence of phreatic surface 687; 11.4.5.5 In- fluence of slope geometry 689; 11.4.5.6 Stability analysis 690 11.4.6 Repair and reinstatement of operational and aban- doned impoundments ...... 691 11.4.6.1 Common problems with old and aban- doned dams 691; Remedial measures 693 11.5 Observation and Control ...... 695 11.6 Closure Considerations ...... 698 x CONTENTS

11.6.1 General ...... 698 11.6.2 Boundary fence ...... 698 11.6.3 Access roadways ...... 700 11.6.4 The underdrainage system ...... 700 11.6.5 The solution or effluent trench ...... 701 11.6.6 The slimes delivery pipeline ...... 701 11.6.7 Surface drainage ...... 701 11.6.8 Ground level catchment paddocks ...... 701 11.6.9 Berms or step-backs ...... 701 11.6.10 The dam surface ...... 703 11.6.11 Return water dam ...... 706 11.7 References...... 706

Chapter 12 Retreatment of Residues and Waste Rock, by D.W. Bosch ...... 707 12.1 Introduction ...... 707 12.2 Origin of Residues ...... 707 12.2.1 Sand dumps and slimes dams ...... 707 12.2.2 Rock dumps ...... 708 12.3 Sampling, Surveying and Valuation ...... 709 12.3.1 Sampling ...... 709 12.3.1.1 Grab sampling 709; 12.3.1.2 Groove or channel sampling 709; 12.3.1.3 Drilling 710 12.3.2 Surveying ...... 711 12.3.2.1 Tacheometric surveys 711; 12.3.2.2 Electronic distance measuring 712; 12.3.2.3 Photogrammetry 712 12.4 Sand/Slime Retreatment Operations ...... 715 12.4.1 Slime reclamation at Blyvooruitzicht Gold Mine 716 12.4.1.1 The bucket-wheel excavator 716; 12.4.1.2 Repulper feed conveyor 719; 12.4.1.3 Repulper 719 12.4.2 Slime reclamation at ERGO ...... 719 12.4.2.1 Location of pump stations 720; 12.4.2.2 Reclamation operations 720; 12.4.2.3 Processing at ERGO 723 12.4.3 Sand and slime reclamation at Rand Mines and Milling ...... 724 12.4.3.1 Process development for sand treatment 724; 12.4.3.2 Reclamation operations 726; 12.4.3.3 Plant operations 727

Xl CONTENTS

12.4.4 The Anglo American Corporation Joint Operating Metallurgical Scheme ...... 731 12.4.4.1 Historical overview 732; 12.4.4.2 Feed sources 733; 12.4.4.3 Flotation plants 733; 12.4.4.4 Treatment of flotation tailings 734; 12.4.4.5 Treatment of pyrite concentrates 735; 12.4.4.6 Treatment of calcine 735 12.5 Waste Rock Recovery and Treatment ...... 736 12.5.1 Development waste ...... 736 12.5.2 Waste rejected from ore setting ...... 737 12.5.3 Radiometric sorting of waste rock...... 738 12.5.4 Waste rock reclamation at the Blyvooruitzicht Gold Mine ...... 738 12.6 of Dumps ...... 740 12.7 Bacterial Leaching of Dumps and Slimes Dams ...... 741 12.7.1 Theoretical aspects ...... 741 12.7.2 by bacteria ...... 742 12.7.3 Slimes dam leaching by bacteria ...... 743 12.8 References...... 743

Chapter 13 Process Evaluation, by H.E. Bartlett and D.M. Hawkins ...... 745 13.1 Introduction...... 745 13.2 Process Evaluation ...... 745 13.3 Statistical Concepts ...... 746 13.3.1 Population, sample, increment and composite samples ...... 746 13.3.2 Accuracy and precision ...... 746 13.3.3 Standard deviation, variance, coefficient of varia- tion ...... 746 13.3.4 Properties of variances and standard deviations 747 13.3.5 Normal and log-normal distribution ...... 748 13.4 Sampling Theory ...... 751 13.4.1 Calculation of the precision of sampling ...... 751 13.4.2 Theoretical calculation of sampling precision using Gy's formulae ...... 751 13.4.3 Gy's '50-piece' experiment ...... 753 13.4.4 Precision of sampling using geostatistical methods 756 13.4.4.1 The semi-variogram 756; l3.4.4.2 Nug- get effect 757; l3.4.4.3 Estimates of variance from semi-variograms 757 13.5 Sampling Practice ...... 759 13.5.1 Run-of-mine ore feed - stop-belt sampling .... 761 CONTENTS

13.5.1.1 Calculation of precision of manual stop­ belt sampling 762; 13.5.1.2 The effect of com­ positing increments into shift and daily samples 763; 13.5.1.3 Accuracy of the sampling proce­ dures 765; 13.5.1.4 Crushing of the sample be­ fore sub-division 765 13.5.2 Automatic sampling of run-of-mine ore ...... 766 13.5.2.1 Testing for bias in automatic sampling 766; 13.5.2.2 Examples of t-tests 768 13.5.3 product sampling ...... 770 13.5.4 Sampling of pulps ...... 771 13.5.4.1 Cross-stream cutters 771; 13.5.4.2 Rotary samplers 773; 13.5.4.3 Precision of sampling with cross-stream cutters 774 13.5.5 Other sampling equipment of pulps ...... 775 13.5.5.1 Pipe sampler 776; 13.5.5.2 Projector sampler 777 13.5.6 Sampling of loaded carbon, , flue dust and other secondary materials at Rand Refinery ... . 777 13.5.7 Sampling of bullion ...... 778 13.5.8 Sampling of liquids ...... 778 13.6 Sampling Preparation ...... 778 13.6.1 Sample preparation equipment and practice .... 778 13.6.1.1 Pulps 778; 13.6.1.2 High grade mate- rials 778; 13.6.1.3 Run-of-mine ore 780 13 .6.2 Statistical methods to quantify bias in sub- sampling ...... 780 13.7 Mass Measurement ...... 780 13 .7.1 Truck and train weighbridges ...... 781 13.7.2 Electromechanical belt massmeters ...... 782 13.7.3 Nuclear belt massmeters ...... 785 13.7.4 Moisture determination for mass measurement 785 13.7.5 Batch mass determination of pulps ...... 786 13.7.6 Batch tanks on load cells...... 786 13.7.7 Mass of pulps using flow and density meters... 786 13.8 Chemical Analysis ...... 787 13.9 Metallurgical Accounting ...... 787 13.9.1 Call system ...... 788 13.9.2 Check-in/ check-out system ...... 789 13.10 Further Developments ...... 790 13.11 References ...... 791

Xlll CONTENTS

Chapter 14 Process Control by I.M. MacLeod and H.E. Bartlett ...... 793 14.1 Introduction ...... 793 14.2 Historical Background ...... 794 14.3 Principles of Continuous Process Control...... 795 14.3.1 Control objectives ...... 795 14.3.2 Classification of process variables ...... 796 14.3.3 Control system structuring ...... 797 14.3.4 The standard three-term industrial controller .. , 800 14.4 Process Measurements ...... 801 14.4.1 Introduction ...... 801 14.4.2 Terminology of instrumentation systems ...... 802 14.4.3 The primary sensing element ...... 803 14.4.4 Accuracy and calibration ...... 803 14.4.5 Basic physical measurements ...... 804 14.4.5.1 Flow rate of solids 804; 14.4.5.2 Flow rate of liquids 804; 14.4.5.3 Liquid level in a vessel 806; 14.4.5.4 The water content of a pulp 807; 14.4.5.5 One-line particle size measurement 807; 14.4.5.6 Basic chemical measurements 810; 14.4.5.7 Carbon and resin concentration meter 815; 14.4.5.8 Carbon activity meter 815 14.5 Actuators and Final Control Elements ...... 817 14.5.1 Introduction ...... 817 14.5.2 Control valves ...... 817 14.5.3 Material feeders ...... 819 14.5.4 Variable-speed drives ...... 819 14.6 Process Control System Design Philosophies and Architec- tures ...... 819 14.6.1 Introduction...... 819 14.6.2 Manual control versus fully automatic control. 820 14.6.3 Hard-wired analogue control systems ...... 821 14.6.4 Centralized computer control systems ...... 822 14.6.5 Distributed computer control systems...... 823 14.6.6 Examples of current practice ...... 824 14.7 References ...... 829

Chapter 15 The Chemistry of the Extraction of Gold, by M.J. Nicol, C.A. Fleming and R.L. Paul...... 831 15.1 General Principles ...... 831 15.1.1 The chemistry of gold compounds ...... 831 15.1.2 An equilibrium approach to the of gold ...... 836 xi'v CONTENTS

15.1. 3 Electrochemical aspects ...... 843 15.1.3.1 Anodic reactions of gold 843; 15.1.3.2 Anodic reactions of 848; 15.1.3.3 Cathodic processes 849 15.2 The Dissolution of Gold ...... 854 15.2.1 The mechanism of cyanidation ...... 854 15.2.2 The effect of other constituents of the pulp .... 857 15.2.2.1 Iron sulphide minerals 858; 15.2.2.2 sulphide minerals 859; 15.2.2.3 Arsenic sulphide minerals 860; 15.2.2.4 Antimony sul- phide minerals 860; 15.2.2.5 Anions containing sulphur 861; 15.2.2.6 Cyanide complexes of various base 861; 15.2.2.7 Calcium ions 862; 15.2.2.8 Carbonaceous material 862; 15.2.2.9 Flotation reagents and other surface ac- tive reagents 863 15.2.3 Other leaching processes ...... 863 15.2.3.1 Thiosulphate 864; 15.2.3.2 Thiourea 864; 15.2.3.3 Thiocyanate 865; 15.2.3.4 Chlo- ride 866 15.3 The Recovery of Gold from Solution ...... 866 15.3.1 Cementation ...... , ...... 866 15.3.2 Extraction by activated carbon, ion-exchange resins or organic solvents ...... 869 15.3.2.1 The activated-carbon process 870; 15.3.2.2 The ion-exchange process 877; 15.3.2.3 The solvent-extraction process 885 15.3.3 Chemical precipitation ...... 889 15.3.4 ...... 890 15.3.4.1 Cell design 890; 15.3.4.2 Electrode reac- tions 893 15.4 Clean-up, and Smelting ...... 894 15.4.1 Acid treatment ...... 895 15.4.2 Calcination...... 896 15.4.3 Smelting ...... 896 15.5 Acknowledgement ...... , ...... " 899 15.6 References...... 899

Chapter 16 Plant Design and Commissioning, by G.G. Stanley ...... 907 16.1 The Importance of Good Plant Design and Punctual Com- missioning ...... 907 16.2 The Design and Construction Organization ...... 907

xv CONTENTS

16.3 Status, Responsibilities and Qualities of the Design - lurgist ...... 908 16.4 General Procedure for Plant Design ...... 908 16.4.1 The procedural plan ...... 908 16.4.2 Ore testing ...... 909 16.4.2.1 Obtaining the sample 909; 16.4.2.2 Mineralogical examination 911; 16.4.2.3 Sample preparation 912; 16.4.2.4 Laboratory testing 913; 16.4.2.5 Pilot plant testing 917 16.4.3 Process design ...... 917 16.4.3.1 Process design criteria 917; 16.4.3.2 Flowsheet design 917; 16.4.3.3 Quantified flow- sheet 918; 16.4.3.4 Equipment sizing and selec- tion 924; 16.4.3.5 Flowsheet evaluation and selection 926; 16.4.3.6 The conclusion of the pro- cess design phase 933 16.4.4 General arrangement ...... 933 16.4.4.1 Site selection 934; 16.4.4.2 Elements of good layout 935; 16.4.4.3 Minimizing transpor- tation requirements 935; 16.4.4.4 Maximizing ease of operation 937; 16.4.4.5 Maximizing ease of maintenance 938; 16.4.4.6 Maximizing ease of supervision 938; 16.4.4.7 Maximizing security 939; 16.4.4.8 Maximizing safety 940; 16.4.4.9 Provision for expansion 940; 16.4.4.10 The use of CAD and models 941 16.4.5 Detailed design ...... 941 16.4.5.1 Plant layout and design details 941; 16.4.5.2 Construction details 953; 16.4.5.3 Piping and instrumentation diagrams 957; 16.4.5.4 The definitive and revised cost estimates 957 16.5 Plant Construction and Commissioning ...... 957 16.5.1 Metallurgical involvement in the construction phase ...... 957 16.5.2 Preparation for commissioning ...... 958 16.5.3 Commissioning ...... 958 16.5.3.1 Personnel 958; 16.5.3.2 Cold commis- sioning 958; 16.5.3.3 Hot commissioning 959; 16.5.3.4 Some practical commissioning tips 960; 16.5.3.5 Acceptance runs 961 16.6 Conclusion ...... 961 16.7 References ...... 961 Appendix 16.1 Pipeline Design...... 963 Appendix 16.2 Pump Selection ...... 967 xvi CONTENTS

Chapter 17 Loss Control and Safety Management, by F.K. Vice and D.l. Nel ...... 971 17.1 Introduction...... 971 17 .2 Loss Control Department ...... 971 17.3 Physical Condition Rating Programme ...... 973 17.4 The Manager's Policy...... 974 17.5 Training...... 974 17.6 Planned Inspections ...... 974 17.6.1 The general inspection ...... 974 17.6.2 Critical parts inspections ...... 975 17.6.2.1 Pre-use inspection of equipment 975 17.7 Accident/Incident Investigation and Analysis ...... 975 17.7.1 The investigation ...... 977 17.7.2 Analysis...... 977 17.7.2.1 Statistical data 977 17.7.3 Benefits derived from accident investigations and analysis ...... 982 17.8 Communications...... 982 17.8.1 Group meetings ...... 982 17.8.2 Personal communication ...... 983 17.9 Emergency Preparedness ...... 983 17.9.1 Care of the injured and ill ...... 985 17.9.2 Hazardous chemicals ...... 985 17.9.3 Fires...... 985 17.9.4 Miscellaneous...... 986 17 .1 0 Physical Examination of Employees ...... 987 17.10.1 Medical examinations ...... 987 17.10.2 Eyesight examinations ...... 987 17.10.3 Audiometric testing ...... 989 17.11 Personal Protective Equipment ...... 991 17.12 Task Analysis and Procedures...... 993 17.12.1 Identification of critical tasks ...... 993 17.12.1.1 Severity 994; 17.12.1.2 Repetitiveness 994; 17.12.1.3 Probability 995; 17.12.1.4 Iden­ tification of tasks requiring procedures, standards or rules 995; 17.12.1.5 Task analysis 996; 17.12.1.6 Critical task inventory summary 996 17.13 Planned Task Observations ...... 999 17.14 and Purchasing Controls ...... 1001 17.15 References...... 1001 Appendix 17.1 Checklist for General Planned Inspection and Physi- cal Condition Ratings ...... 1002

XVll CONTENTS

Chapter 18 Laboratories and Pilot Plants, by C. W.A. Muir 1013 18.1 Introduction ...... 1013 18.2 Characteristics of Metallurgical Laboratories of the Gold Mining Industry...... 1015 18.2.1 On-mine laboratories ...... 1015 18.2.1.1 Layout 1015; 18.2.1.2 Equipment 1017; 18.2.1.3 Functions 1019; 18.2.1.4 Staffing 1019; 18.2.1.5 Comment 1020 18.2.2 Group laboratories ...... 1020 18.2.2.1 Layout 1022; 18.2.2.2 Equipment 1022; 18.2.2.3 Functions 1023; 18.2.2.4 Staffing 1025 18.3 Mintek 1026 18.3.1 Introduction ...... 1026 18.3.2 Categories of sponsorship and conditions pertain- ing to them ...... 1027 18.3.3 The facilities at Mintek ...... 1028 18.4 Pilot Plants ...... 1029 18.4.1 Reasons for piloting ...... 1029 18.4.2 Types of pilot plants ...... 1030 18.4.3 Scale-up factors ...... 1030 18.4.4 Design of pilot plants ...... 1031 18.4.5 Operation of pilot plants ...... 1031 18.4.6 Pilot plant location ...... 1031 18.4.7 Type of investigation carried out in pilot plants 1032 18.5 References...... 1033 Appendix 18.1 Determination of Relative Grindability using a Labcr ratory Batch Rod ...... 1034 Appendix 18.2 Standard Procedure for Routine Size Analysis of Finish-ground Products ...... 1036 Appendix 18.3 Determination of Thickener Area ...... 1041 Appendix 18.4 Filtration Rate Determination ...... 1044 Appendix 18.5 Cyanidation Tests using Rolling Bottle Method.. 1047 Appendix 18.6 Muffle of Sulphide Concentrates ...... 1049 Appendix 18.7 Determination of Activated Carbon Parameters. 1050

Tables and Formulae, by W.R. Flook ...... 1053 Note on conversion tables ...... 1054 Table 1 Conversion table: length ...... 1055 Table 2 Conversion table: area ...... 1056 Table 3 Conversion table: volume ...... 1057 Table 4 Conversion table: velocity...... 1058 Table 5 Conversion table: rate of flow...... 1058 Table 6 Conversion table: mass ...... 1059

X-'Vl11 CONTENTS

Table 7 Conversion table: pressure...... 1060 Table 8 Conversion table: energy ...... 1060 Table 9 Conversion table: power ...... 1061 Table 10 Conversion table: density ...... 1061 Table 11 Some fundamental constants ...... 1062 Table 12 Moisture content, density, etc. of pulps ...... 1062 Table 13 Formulae ...... 1064 Table 14 Base units of the International System ...... 1067 Table 15 Derived units of the International System ...... 1067 Table 16 S I prefixes ...... 1068 Table 17 Critical speed of mills ...... 1068 Table 18 Te~ting-sieve series ...... 1069 Table 19 The periodic table ...... 1071 Table 20 The Greek alphabet ...... 1072

Index ...... 1073

VOLUME 1

Note: These contents have been abbreviated by omission of the third level of subheading.

Chapter 1 Geology and Mineralogy of the Principal Goldfields in South Africa, by C.R. Anhaeusser, C.E. Feather, W.R. Liebenberg, G. Smits and l.A. Snegg ...... 1.1 Historical Background ...... 1 1.2 Gold in the Sediments of the Witwatersrand Triad ...... 5 1.2.1 Geological aspects ...... 5 1.2.2 Macroscopic description of the placers ...... 13 1.2.3 Mineral composition of the placers ...... 15 1.2.4 Nature and mode of occurrence of the gold .... 16 1.2.5 Distribution of gold and heavy minerals ...... 26 1.2.6 Chemical composition of the gold ...... 28 1.2.7 Gold in residues ...... 30 1.2.8 Other minerals of economic interest ...... 33 1.3 Gold in the Barberton Mountain Land ...... 35 1.3.1 Introduction...... 35 1.3.2 General geology...... 37 1.3.3 Gold distribution in the Barberton Mountain Land 41

xix CONTENTS

1.3.4 Mineralogical aspects of the Barberton gold 49 1.3.5 Refractory ores and their treatment ...... 58 1.3.6 Origin of the Barberton gold deposits ...... 60 1.4 References...... 60

Chapter 2 S0I1ing and Crushing, by G. G. Stanley ...... 69 2.1 Introduction ...... 69 2.1.1 Mining methods ...... 69 2.1.2 Underground waste sorting ...... 70 2.1.3 The nature of the run-of-mine ore ...... 70 2.1.4 The operations carried out in the sorting and crushing plant ...... 72 2.2 Ore Transport to the Treatment Plant ...... 75 2.2.1 Skip transport ...... 75 2.2.2 Endless rope haulages ...... 75 2.2.3 Rail transport...... 75 2.2.4 Road transport ...... 76 2.2.5 Overhead ropeways ...... 76 2.2.6 Belt conveyors...... 76 2.3 Ore Storage, Feeding and In-Plant Conveying ...... 76 2.3.1 Ore storage ...... 76 2.3.2 Feeders ...... 80 2.3.3 In-plant conveying ...... 85 2.4 Washing ...... 91 2.4.1 Washing in chutes ...... 92 2.4.2 Washing on conveyor belts ...... 92 2.4.3 Washing on grizzlies ...... 92 2.4.4 Washing in trommels ...... 92 2.4.5 Washing on vibrating screens ...... 93 2.4.6 Dealing with washings ...... 94 2.5 Sizing ...... 94 2.5.1 Grizzlies ...... 94 2.5.2 Vibrating screens ...... 95 2.6 Crushing ...... 98 2.6.1 Types of crusher ...... 98 2.7 Waste Sorting and Reef Picking ...... 107 2.7.1 Definition of waste sorting ...... 107 2.7.2 Manual sorting ...... 107 2.7.3 Mechanized sorting ...... 108 2.7.4 Reef picking ...... 111 2.7.5 Disposal of reject rock ...... 111 2.7.6 Economics of waste sorting ...... 113

xx CONTENTS

2.8 Selection of Grinding Media for Pebble Milling...... 114 2.8.1 Manual pebble selection ...... 114 2.8.2 Pebble selection by grizzley or vibrating screen 114 2.8.3 Pebble selection by deflection of the entire ore stream ...... 115 2.8.4 Pebble storage and transport...... 115 2.9 Mass Measurement, Sampling and Control...... 115 2.9.1 Mass measurement ...... 115 2.9.2 Sampling ...... 116 2.9.3 Control ...... 116 2.10 Safety and Health ...... 117 2.10.1 Regulations ...... 117 2.10.2 Dust suppression...... 117 2.10.3 Noise suppression ...... 119 2.11 References...... 119

Chapter 3 Milling and Classification, by G. G. Stanley ... 121 3.1 Evolution of the Milling Techniques Used in the Treatment of South African Gold Ores ...... 121 3.2 Theory of Milling ...... 125 3.2.1 Terminology and definition...... 125 3.2.2 The reasons for grinding ...... 125 3.2.3 The boundary between crushing and grinding.. 127 3.2.4 The process of brittle fracture resulting from com- pression ...... , ...... 128 3.2.5 The particle size distribution resulting from brittle fracture ...... 129 3.2.6 The determination and reporting of size distribu- tion ...... 129 3.2.7 Mathematical descriptions of size distributions 131 3.2.8 Mechanisms of size reduction and transport within tumbling mills ...... 135 3.2.9 Energy requirements of ...... 139 3.2.10 Stage grinding ...... 143 3.2.11 Closed circuiting ...... 147 3.2.12 Summary of basic milling theory ...... 152 3.3 Types of Tumbling Mill and their Characteristics ...... 152 3.3.1 General description ...... 152 3.3.2 Rod mills ...... 157 3.3.3 Ball mills...... 158 3.3.4 Autogenous mills ...... 160 3.3.5 Milling combinations ...... 162 3.4 Mill Feeders ...... 163 3 .4.1 Scoop feeders ...... 163

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3.4.2 Drum feeders ...... 164 3.4.3 Spout feeders ...... 164 3.4.4 Hopper feeders ...... 165 3.5 Mill Liners ...... 166 3.5.1 Trunnion liners ...... 166 3.5.2 Inlet end liners ...... 167 3.5.3 Outlet end liners ...... 167 3.5.4 Shell liners ...... 170 3.5.5 Summary of South African liner practice ...... 175 3.5.6 Relining methods ...... 175 3.6 Grinding Media ...... 178 3.6.1 Rods ...... 178 3.6.2 Balls...... 179 3.6.3 Pebbles...... 179 3.6.4 Grinding medium size for given ore feed size.. 179 3.6.5 Nature of grinding medium wear ...... 181 3.6.6 The ball-wear theories of Davis and Prentice ... 182 3.6.7 Ball rationing ...... 183 3.7 Ancillary Equipment ...... 184 3 .7.1 Feeders...... 184 3.7.2 Massmeters ...... 187 3.7.3 Pumps ...... 187 3.7.4 Pipes ...... 188 3.7.5 Valves ...... 188 3.7.6 Distributors ...... 188 3.7.7 Water reticulation ...... 189 3.8 Principles of Mill Operation ...... 189 3.8.1 Basic objectives ...... 189 3.8.2 Maximizing energy availability...... 189 3.8.3 The effect of feed size distribution in ROM and SAG mills ...... 195 3.8.4 Maximizing utilization of the available power.. 196 3.8.5 Automatic control...... 199 3.9 References...... 201 Appendix 3.1 Hydrocyclone classifier theory, modelling and design 204 Appendix 3.2 Classification formulae ...... 209 Appendix 3.3 Pebble competence testing and autogenous grindabili- ty determination...... 210 Appendix 3.4 Mill design methods ...... 212 Appendix 3.5 Determining grinding energy requirements for materials that are already finer than the feed size (3350 j-tm) specified for the Bond Grindability Test ...... 216 Appendix 3.6 Derivation of Equation 3.22 relating ball mass in load, daily ball feed rate, new ball diameter and daily ball wear rate ...... 217

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Chapter 4 Gravity Concentration, by D.W. Penman ...... 219 4.1 Introduction ...... , ...... 219 4.1.1 Historical...... 219 4.1.2 The rationale of concentration ...... 219 4.1.3 Historical background ...... 220 4.1.4 Present philosophy and practice ...... 221 4.2 Advantages and Disadvantages of Gravity Concentration 221 4.3 Equipment ...... 223 4.3.1 Corduroy blankets ...... 223 4.3.2 Johnson drum concentrator ...... 224 4.3.3 Plane table ...... 225 4.3.4 Jigs ...... 226 4.3.5 Endless riffle belts ...... 226 4.3.6 Shaking tables ...... 227 4.3.7 Mill liners ...... 228 4.4 Concentrate Treatment ...... 228 4.4.1 Re-dressing and smelting ...... 228 4.4.2 Roasting and cyanidation ...... 228 4.4.3 Amalgamation ...... 229 4.4.4 Intensive cyanidation ...... 230 4.4.5 Iron removal...... 230 4.5 Gravity Concentration Circuits ...... 231 4.5.1 President Steyn gravity circuit ...... 231 4.5.2 Gravity concentration at Sheba ...... 232 4.6 Development ...... 233 4.7 References ...... 234 Chapter 5 Flotation, by B.R. Broekman, L.A.C. Carter and R. C. Dunne ...... 235 5.1 Introduction ...... , ...... 235 5.2 Flotation Processing ...... 236 5.2.1 Mineralogical aspects ...... 236 5.2.2 Process aspects ...... 238 5.2.3 Flotation plant practice ...... 251 5.3 Current Flotation Trends ...... 260 5.3.1 Equipment ...... 260 5.3.2 Design ...... 261 5.3.3 Control ...... 265 5.3.4 Trouble-shooting methods ...... 266 5.3.5 New flotation applications ...... 272 5.4 References

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Chapter 6 Cyanidation, by G.J.C. Young ...... 277 6.1 Introduction ...... 277 6.2 Thickening ...... 277 6.2.1 Batch thickeners or collectors ...... 277 6.2.2 Continuous thickeners...... 278 6.2.3 High-rate thickeners ...... 290 6.3 Leaching ...... 291 6.3.1 Leaching reagents ...... 291 6.3.2 Batch and continuous leaching ...... 295 6.3.3 Leaching vessels ...... 301 6.3.4 Leaching conditions ...... 303 6.3.5 Gold losses ...... 304 6.4 Liquid-solid Separation ...... 305 6.4.1 Filtration ...... 305 6.4.2 Filter practice...... 312 6.4.3 Maintenance ...... 316 6.4.4 Capacities ...... 317 6.5 Clarification ...... 317 6.5.1 Clarifier types ...... 318 6.6 References ...... 323 Appendix 6.1 Thickener design calculations ...... 324 Appendix 6.2 Leaching design calculations ...... 326 Appendix 6.3 A note on the development of an on-stream analyser for cyanide concentration, pH and alkalinity ...... 328 Appendix 6.4 The determination of nett dissolved gold loss (DO Nett) ...... 328 Chapter 7 Recovery of Gold from Solution by Cementation, by D. Bosley ...... 331 7.1 Introduction...... 331 7.1.1 Characteristics of gold bearing solutions...... 331 7.1.2 Recovery methods ...... 331 7.2 Zinc Dust Precipitation...... 333 7.2.1 Solution preparation ...... 333 7.2.2 Precipitation practice ...... 337 7.3 References...... 343

Chapter 8 pyrometallurgy of Gold, by 0.1. Gossman.... 345 8.1 Introduction...... 345 8.2 Roasting of Concentrates ...... 345 8.2.1 Introduction...... 345 8.2.2 Basic chemistry of the roasting process ...... 346

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8.2.3 Roasting furnaces ...... 348 8.2.4 Roaster gas treatment ...... 350 8.2.5 Status of roasting in South African gold metallurgy 351 8.3 Retorting of Gold ...... 352 8.3.1 Introduction ...... 352 8.3.2 The retort furnace ...... 352 8.3.3 Mercury hazard ...... 353 8.3.3.1 Precautions when handling mercury 354 8.4 Calcining of Zinc-Gold Precipitate ...... 354 8.4.1 Introduction ...... 354 8.4.2 Clean-up of zinc-gold precipitate...... 355 8.4.3 Acid treatment of zinc-gold precipitate ...... 356 8.4.4 Dewatering of gold slime...... 357 8.4.5 Calcining of gold slime ...... 361 8.5 Smelting gold bearing Material...... 363 8.5.1 Introduction ...... 363 8.5.2 Fusion furnaces ...... 363 8.5.3 Direct smelting of gold concentrates ...... 369 8.5.4 Melting of sponge gold ...... 369 8.5.5 Smelting of calcined slime ...... 370 8.5.6 Smelting of steelwool cathodes ...... 372 8.5.7 Cleaning and sampling gold bars ...... 373 8.5.8 Slag handling ...... 375 8.5.9 Safety hazards in the smelthouse ...... 375 8.6 Dust and Fume Extraction ...... 376 8.7 Precautions against Gold Theft ...... 376 8.8 Record Keeping ...... 377 Chapter 9 Application of Activated Carbon to Gold Recovery, by P.R. Bailey...... 379 9.1 Introduction...... 379 9.1.1 Historical ...... 379 9.1.2 Gold recovery ...... 379 9.1.3 Process route comparisons ...... 382 9.2 Activated Carbon ...... 383 9.2.1 Physical and chemical properties ...... 384 9.2.2 Gold absorbing properties ...... 387 9.3 Absorption ...... 393 9.3.1 Modelling ...... 393 9.3.2 Stage, loading and barren values ...... 399 9.3.3 Equilibrium effects ...... 417 9.3.4 Carbon activity ...... 429 9.3.5 Physical effects ...... 439

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9.3.6 Operating considerations ...... 443 9.3.7 Carbon-in-leach operations ...... 449 9.3.8 Other feed stocks ...... 455 9.3.9 Equipment ...... 457 9.4 Elution 481 9.4.1 Introduction ...... 481 9.4.2 Physical and chemical effects ...... 483 9.4.3 Kinetics of elution ...... 489 9.4.4 Anglo American Research Laboratory (AARL) elution ...... 492 9.4.5 Zadra elution ...... 503 9.4.6 Equipment ...... 511 9.5 Regeneration ...... 530 9.5.1 Introduction ...... 530 9.5.2 Thermal regeneration ...... 530 9.5.3 Rotary kilns ...... 541 9.5.4 Rintoul kiln regeneration ...... 547 9.6 Electrowinning ...... 550 9.6.1 Electrochemical reactions ...... 551 9.6.2 Cell design ...... 552 9.6.3 Electrowinning cells ...... 554 9.6.4 Mintek cell - operational data ...... 561 9.7 Acid Treatment ...... 570 9.7.1 Acid treatment conditions ...... 571 9.8 Carbon Breakage ...... 575 9.8.1 Breakage by pumps ...... 575 9.8.2 Breakage by eductors ...... 581 9.8.3 Breakage by mixing ...... 583 9.8.4 Breakage during regeneration ...... 583 9.8.5 Plant carbon loss ...... 584 9.9 Carbon in Solution ...... 585 9.9.1 Adsorption systems ...... 585 9.9.2 Design considerations ...... 599 9.10 References ...... 608

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