Vol II Appendix D – Process Design Criteria

1522 Pages·2012·38.39 MB·English

Report to:
V G C .
ISTA OLD ORP

7961 Shaffer Parkway, Suite 5, Littleton, CO 80127
Phone: [phone])

NI 43-101 Technical Report – Mt. Todd Gold Project
50,000 tpd Preliminary Feasibility Study
Northern Territory, Australia

Appendix D
Process Design Criteria for Processing
50,000 tpd

PROJECT NO. 114-311285

DATE: JUNE 2013

PREPARED BY: ALS/ASMMTEC

350 Indiana Street, Suite 500, Golden, CO 80401
Phone: [phone] Fax: [phone]
Metallurgical Testwork
conducted upon
Gold Ore Samples from the
Mt Todd Project Feasibility Study
for
Vista Gold Australia Pty Ltd

Report No. A13575 Part 1

May 2012

The results contained in this report relate only to the sample(s) submitted for testing.
ALS Ammtec accepts no responsibility for the representativeness of the sample(s) submitted.
Report No. A13575 Part 1

TABLE OF CONTENTS

PAGE NO.

SUMMARY (i)

1. INTRODUCTION 1
2. THE SAMPLES 3
3. SAMPLE PREPARATION 4
3.1 Procedure 4
3.1.1 Mt Todd Near-Surface Gold Ore Composite (Figures 1A and
1AA) 4
3.1.2 Mt Todd Deep U/G Gold Ore Composite (Figures 1B and
1BB) 4
3.1.3 Mt Todd Variability Gold Ore Drill Core material (Figure 1C) 4
3.1.4 Bond Master Composite (Figure 1D) 4
3.1.5 MHT001 Master Composite (Figure 1E) 5
3.1.6 MHT004 Master Composite (Figure 1F) 5
3.1.7 MHT001 Master Composite Polysius HPGR Product (Figure
1G) 5
3.1.8 MHT004 Master Composite Polysius HPGR Product (Figure
1H) 5
3.1.9 MHT001 Plant Feed Master Composite (Figure 2) 5
3.1.10 Mt Todd Feed (Overall) Master Composite (Figure 2A and
2C) 5
3.1.11 Mt Todd Plant Feed Overall Master Composite (Figure 2B) 5
3.1.12 Mt Todd Master Composite (ex-A13575) (Figures 2D, 2E
and 2F) 6
3.1.13 Variability Composite 79 (VB11 003 519-535m) (Figure 2E) 6
3.1.14 Mt Todd Drill Core Gold Ore Variability Samples #1-99
(Figure 3) 6
3.1.15 Mt Todd Single Feed Master Composite (Figure 4) 6
3.1.16 TUNRA Waste Composite (Figure 6) 6
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

3.1.17 Mt Todd Variability Composites (Figure 7) 6
3.1.18 Mt Todd Gold Ore Bulk Sample (Year 2010 Drill Core)
(Figure 8) 7
3.1.19 Mt Todd Gold Ore Bulk Sample HPGR Centre Product
(Figure 9) 7
3.1.20 Mt Todd Gold Ore Bulk -32 mm Conventional Crush Sample
(Figure 10) 7
4. TESTWORK WATER 8
5. TEST AND ANALYTICAL PROCEDURES 8
5.1 Unconfined Compressive Strength (UCS) Determination 8
5.1.1 Test Procedure 8
5.2 Bond Impact Crushing Work Index Determination (CWi) 9
5.2.1 Test Procedure 9
5.3 SAG Mill Comminution (SMC) Testwork 10
5.3.1 Test Procedure 11
5.4 Bond Ball Mill Work Index Determination 12
5.4.1 Test Procedure 12
5.5 Grind Establishment Testwork 13
5.5.1 Test Procedure 13
5.6 Direct Cyanidation Leach Testwork 14
5.6.1 Test Procedure 14
5.7 CIL Cyanidation Leach Testwork 15
5.7.1 Test Procedure 15
5.8 Sequential Triple Contact Carbon Adsorption CIP Testwork 16
5.8.1 Test Procedure 16
5.9 Oxygen Uptake Rate Determination 17
5.9.1 Test Procedure 17
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

5.10 Slurry Rheology 17
5.10.1 Test Procedure 17
5.11 HPGR Testwork 18
5.11.1 Bulk Density and Moisture Determinations 18
5.11.1.1 Test Procedure 18
5.11.2 HPGR Testwork 18
5.11.2.1 Test Procedure 18
5.11.3 HPGR Feed Particle Size Distribution Determinations 19
5.11.3.1 Test Procedure 19
5.11.4 Single Pass HPGR Test Product Particle Size Distribution
Determination 19
5.11.4.1 Test Procedure 19
5.12 Wet and Dry, Low Intensity Magnetic Separation (LIMS) 20
5.12.1 Test Procedure 20
5.13 Cyanide Detoxification SO /Air Method 20
2
5.13.1 Test Procedure 20
5.14 Analytical Methods 21
6. MHT001 MT TODD NEAR SURFACE GOLD ORE/MHT001 MASTER
COMPOSITE 22
6.1 Comminution Testwork 22
6.1.1 Results 22
6.1.1.1 Bond Impact Crushing Work Index (CWi)
Determination 22
6.1.1.2 Unconfined Compressive Strength (UCS) Testwork 22
6.2 MHT001 Master Composite Preparation 23
6.3 HPGR Product Testwork 23
6.3.1 MT001 M2.3 Centre -6.00 mm HPGR 23
6.3.1.1 Results 23
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

6.3.2 Bond Ball Mill Work Index Determination 24
6.3.2.1 Results 24
6.4 Extraction Testwork 25
6.4.1 Analysis of Head Sample 25
6.4.1.1 Results 25
6.4.2 Grind Establishment Testwork 26
6.4.2.1 Grind Times 26
6.4.3 HPGR and Conventional Crushed Sample Extraction
Testwork 26
6.4.3.1 Results 26
6.4.3.2 Comments 27
7. MHT004 MT TODD DEEP U/G GOLD ORE/ MHT004 MASTER
COMPOSITE TESTWORK 28
7.1 Comminution Testwork 28
7.1.1 Bond Impact Crushing Work Index (CWi) Determination 28
7.1.1.1 Results 28
7.1.2 Unconfined Compressive Strength (UCS) Testwork 29
7.1.2.1 Results 29
7.2 MHT004 Master Composite Preparation 30
7.3 HPGR Product Testwork 30
7.3.1 MT004 M2.3 Centre -6.00 mm HPGR 30
7.3.1.1 Results 30
7.3.2 Bond Ball Mill Work Index Determination 30
7.3.2.1 Results 30
7.4 Extraction Testwork 31
7.4.1 Analysis of Head Sample 31
7.4.1.1 Results 31
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

7.4.2 Grind Establishment Testwork for HPGR and Conventional
Crushed Product 32
7.4.2.1 Grind Times 32
7.4.3 HPGR and Conventional Crush Extraction Testwork 32
7.4.3.1 Results 32
7.4.3.2 Comments 33
8. MT TODD VARIABILITY GOLD ORE DRILL CORE TESTWORK 34
8.1 Comminution Testwork 34
8.1.1 SMC Testwork 34
8.1.1.1 Results 34
8.1.2 Bond Ball Mill Work Index Determination 35
8.1.2.1 Results 35
8.2 Dry Low Intensity Magnetic Separation (LIMS) 36
8.3 Mineralogical Examination (MLA) 36
8.3.1 Composite #16 VB11-001 349-360 m 36
8.3.2 Composite #19 VB11-001 380-391 m 37
8.3.3 Composite #26 VB11-001 456-467 m 37
8.3.4 Composite #33 VB12–002 284–294 m 37
8.3.5 Composite #39 VB12–002 345–355 m 37
8.3.6 Composite #91 VB12–010 18.80–29.92 m 37
8.4 Analysis of Head Sample 38
8.4.1 Results 38
8.4.2 Comments 41
8.5 Extraction Testwork 42
8.5.1 CIL Cyanidation Leach Testwork - P Grind Size 125 µm 42
80
8.5.1.1 Results 42
8.5.1.2 Comments 45
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

8.5.2 Grind Size Optimisation CIL Cyanidation Leach Testwork -
P Grind Size 90 µm 48
80
8.5.2.1 Results 48
8.5.2.2 Comments 49
8.6 Bond Ball Mill Work Index Determination – Comminution
Testwork Extension 51
8.6.1 Results 51
8.6.2 Comments 54
9. BOND MASTER COMPOSITE TESTWORK 55
9.1 Results 55
9.2 Comments 55
10. MT TODD MASTER COMPOSITE/SINGLE PLANT FEED MASTER
COMPOSITE 56
10.1 Comminution Testwork 56
10.1.1 Bond Ball Mill Work Index Determination 56
10.1.1.1 Results 56
10.2 Oxygen Uptake Rate Determination 57
10.2.1 Results 57
10.2.2 Comments 57
10.3 Optimisation CIL Cyanidation Leach Testwork 58
10.3.1 Analysis of Head Sample 58
10.3.1.1 Results 58
10.3.1.2 Comments 58
10.3.2 Grind Establishment Testwork 59
10.3.2.1 Grind Times 59
10.3.3 Grind Optimisation – CIL Cyanidation Testwork 59
10.3.3.1 Results 60
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

10.3.4 Pre-Oxygenation Stage Optimisation – CIL Cyanidation
Leach Testwork 61
10.3.4.1 Results 61
10.3.4.2 Comments 61
10.4 Direct Cyanidation Leach Testwork 62
10.4.1 Air/Oxygen/No Sparge Optimisation – Direct Cyanidation
Leach Testwork 62
10.4.1.1 Results 62
10.4.1.2 Comments 62
10.4.2 Cyanide Dosage Optimisation - Direct Cyanidation
Testwork 63
10.4.2.1 Results 63
10.4.2.2 Comments 63
10.4.3 Pulp Density Optimisation – Direct Cyanidation Leach
Testwork 64
10.4.3.1 Results 64
10.4.3.2 Comments 64
10.4.4 Direct Cyanidation Testwork with Optimum Lead Nitrate
Addition 65
10.4.4.1 Results 65
10.4.4.2 Comments 65
10.5 Extraction Testwork at Pulp Density 60% Solids 66
10.5.1 Direct Cyanidation Testwork – Lime in Mill/Leach with
Selected Pre-Conditioning Stage 66
10.5.1.1 Results 66
10.5.1.2 Comments 66
10.5.2 Direct Cyanidation Testwork - Lead Nitrate Addition
Optimisation with Selected Pre-Conditioning Stage 67
10.5.2.1 Results 67
10.5.2.2 Comments 67
Report No. A13575 Part 1

TABLE OF CONTENTS (Cont’d)

PAGE NO.

10.5.3 CIL Cyanidation Testwork at Optimum Pulp Density and
Lead Nitrate Addition 100 g/t Compare – Reagent Addition
Optimisation 68
10.5.3.1 Results 68
10.5.3.2 Comments 68
10.5.4 Grind Optimisation CIL Cyanidation Testwork 69
10.5.4.1 Results 69
10.5.4.2 Comments 69
10.6 Bulk Cyanidation Direct Time Leach Testwork under Optimum
Leach Conditions followed by Sequential Triple Contact CIP 70
10.6.1 Results 70
10.6.2 Fleming Adsorption Constant Determination 71
10.6.2.1 Results 71
10.7 Cyanide Detoxification Testwork and Geochemical Tailings
Testwork on Detoxification Products 72
10.7.1 Bulk Cyanide CIL Cyanidation Leach Testwork in Duplicate 72
10.7.1.1 Results 72
10.7.2 Cyanide Detoxification Tests using the SO /Air Process 73
2
10.7.2.1 Results 73
10.7.3 Cyanide Detoxification Product Geochemical Analysis 74
10.7.3.1 Results 74
10.8 Mixer Design Testwork – Testing (Sizing) the CIL Tank Agitator
(SPX Flow Technology) 75
10.8.1 Comments 75
10.9 Thickening of Gold Cyclone Overflow Slurry Prior to Gold
Leach Stage (Outotec) 76
10.9.1 Comments 76
10.10 Slurry Rheology Testwork 76