St Ives gold mine - Mineral Resources and Mineral Reserves
Geology and evaluation models have been updated to reflect the latest available data sets. An integrated mine design and schedule is based on current performance levels and takes cognisance of any inherent risks associated with mining operations at St Ives.
The Mineral Resources are classified as Measured, Indicated and Inferred as defined in the SAMREC Code. Increasing levels of geoscientific knowledge and confidence are based on geological understanding, grade variance, drill hole/sample spacing, mining development (amount of exposed and mapped mineralisation) and mining history. The economic evaluation is based on the Company planning gold price, taking into account estimates of all costs, the impact of modifying factors such as mining dilution and metal/ore recovery, processing recovery and royalties. All Mineral Resources and Mineral Reserves reported are 100% attributable to St Ives.
Mineral Resources
The Mineral Resources and Mineral Reserves have been updated using the current planning gold price of A$1,850/oz and A$1,600/oz respectively and reported in accordance with the SAMREC Code. The surface sources include stockpiles that are supported by adequate sampling, and are thus classified as Measured Mineral Resources.
Mineral Resource classification
Tonnes (kt) | Grade (g/t) | Gold (koz) | ||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Classification | Dec 2017 | Dec 2016 | Dec 2015 | Dec 2017 | Dec 2016 | Dec 2015 | Dec 2017 | Dec 2016 | Dec 2015 | |||||||||||
Open pit and underground | ||||||||||||||||||||
Measured | 1,356 | 2,291 | 1,268 | 3.89 | 3.26 | 4.59 | 169 | 240 | 187 | |||||||||||
Indicated | 22,164 | 17,980 | 17,905 | 3.85 | 3.81 | 3.41 | 2,744 | 2,203 | 1,961 | |||||||||||
Inferred | 7,467 | 6,538 | 6,981 | 3.31 | 3.56 | 4.06 | 795 | 747 | 912 | |||||||||||
Total open pit and underground | 30,987 | 26,809 | 26,155 | 3.72 | 3.70 | 3.64 | 3,709 | 3,191 | 3,061 | |||||||||||
Surface | ||||||||||||||||||||
Measured stockpiles | 3,457 | 3,317 | 2,967 | 1.25 | 1.00 | 0.85 | 139 | 107 | 81 | |||||||||||
Total surface | 3,457 | 3,317 | 2,967 | 1.25 | 1.00 | 0.85 | 139 | 107 | 81 | |||||||||||
Grand total | 34,445 | 30,126 | 29,122 | 3.47 | 3.40 | 3.35 | 3,847 | 3,297 | 3,141 |
Mineral Resource classification per mining area
Measured | Indicated | Inferred | Total Mineral Resource | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Area | Tonnes (kt) | Grade (g/t) | Gold (koz) | Tonnes (kt) | Grade (g/t) | Gold (koz) | Tonnes (kt) | Grade (g/t) | Gold (koz) | Tonnes (kt) | Grade (g/t) | Gold (koz) | |||||||
Open pit | |||||||||||||||||||
APN | – | – | – | 251 | 7.35 | 59 | – | – | – | 251 | 7.35 | 59 | |||||||
Incredible | - | – | – | 1,273 | 1.90 | 78 | 442 | 2.17 | 31 | 1,715 | 1.97 | 109 | |||||||
Invincible Pit | 556 | 3.36 | 60 | 1,164 | 3.90 | 146 | 67 | 3.04 | 7 | 1,786 | 3.70 | 212 | |||||||
Justice | – | – | – | 559 | 2.57 | 46 | 175 | 2.91 | 16 | 735 | 2.65 | 63 | |||||||
Neptune | 174 | 4.52 | 25 | 3,790 | 2.81 | 343 | 802 | 2.43 | 63 | 4,766 | 2.81 | 431 | |||||||
Pistol Club | – | – | – | 536 | 3.77 | 65 | 43 | 1.80 | 3 | 579 | 3.62 | 67 | |||||||
Santa Ana | – | – | – | 1,531 | 2.20 | 108 | 99 | 1.85 | 6 | 1,630 | 2.17 | 114 | |||||||
Yorick | – | – | – | 91 | 4.50 | 13 | 448 | 3.29 | 47 | 539 | 3.50 | 61 | |||||||
Other | 25 | 2.23 | 2 | 1,956 | 3.06 | 192 | 892 | 2.82 | 80 | 2,873 | 2.98 | 275 | |||||||
Total open pit | 755 | 3.58 | 87 | 11,151 | 2.93 | 1,051 | 2,970 | 2.67 | 253 | 14,875 | 2.91 | 1,391 | |||||||
Underground | |||||||||||||||||||
Argo | 122 | 4.45 | 17 | 601 | 4.30 | 83 | 316 | 3.46 | 35 | 1,040 | 4.06 | 136 | |||||||
Cave Rocks | 90 | 3.47 | 10 | 247 | 3.83 | 30 | 339 | 4.26 | 46 | 676 | 4.00 | 87 | |||||||
hamlet | 179 | 5.66 | 32 | 1,304 | 4.29 | 180 | 45 | 4.03 | 6 | 1,528 | 4.44 | 218 | |||||||
Invincible UG | – | – | – | 4,812 | 4.93 | 763 | 1,764 | 4.26 | 242 | 6,576 | 4.75 | 1,005 | |||||||
Invincible South | – | – | – | 1,580 | 7.24 | 368 | 467 | 4.87 | 73 | 2,047 | 6.70 | 441 | |||||||
North Orchin | – | – | – | 570 | 4.28 | 78 | 699 | 3.51 | 79 | 1,269 | 3.85 | 157 | |||||||
Sirius | 211 | 3.29 | 22 | 1,899 | 3.13 | 191 | 867 | 2.17 | 61 | 2,977 | 2.86 | 274 | |||||||
Total underground | 602 | 4.24 | 82 | 11,013 | 4.78 | 1,694 | 4,497 | 3.75 | 542 | 16,112 | 4.48 | 2,318 | |||||||
Surface | |||||||||||||||||||
Surface stockpiles | 3,457 | 1.25 | 139 | – | – | – | – | – | – | 3,457 | 1.25 | 139 | |||||||
Grand total | 4,814 | 2.00 | 308 | 22,164 | 3.85 | 2,744 | 7,467 | 3.32 | 797 | 34,445 | 3.48 | 3,847 |
Modifying factors
- All Mineral Reserves are quoted in terms of RoM grades and tonnages, as delivered to the metallurgical processing facilities, and are therefore fully diluted
- The Mineral Reserve Statements include only Measured and Indicated Mineral Resources, modified to produce Mineral Reserves that are contained in the LoM plan
- Mineral Resources and Mineral Reserves undergo regular internal and/or external audits, and any issues identified are rectified at the earliest opportunity – usually during current reporting cycle
- The Measured and Indicated Mineral Resources are inclusive of Mineral Reserves
December | ||||||||
---|---|---|---|---|---|---|---|---|
Units | 2017 | 2016 | 2015 | |||||
Mineral Resource parameters | ||||||||
Mineral Resource gold price | US$/oz | 1,400 | 1,400 | 1,500 | ||||
A$/oz | 1,850 | 1,850 | 1,750 | |||||
Cut-off for oxide ore | g/t | 0.74 – 0.93 | 0.55 – 0.96 | 0.55 – 1.06 | ||||
Cut-off for fresh ore | g/t | 0.74 – 3.1 | 0.55 – 3.2 | 0.55 – 3.5 | ||||
Cut-off for mill feed | g/t | 0.74 – 0.95 | 0.55 – 0.96 | 0.55 – 1.06 | ||||
Cut-off for open pit | g/t | 0.74 – 0.95 | 0.55 – 0.96 | 0.55 – 1.06 | ||||
Cut-off for underground | g/t | 1.8 – 3.1 | 2.4 – 3.2 | 2.4 – 3.5 | ||||
Mineral Reserve parameters | ||||||||
Mineral Reserve gold price | US$/oz | 1,200 | 1,200 | 1,300 | ||||
A$/oz | 1,600 | 1,600 | 1,550 | |||||
Cut-off for oxide ore | g/t | 0.4 | 0.5 | 0.55 – 0.95 | ||||
Cut-off for fresh ore | g/t | 0.4 – 2.9 | 0.50 – 3.0 | 0.55 – 3.0 | ||||
Cut-off for mill feed underground | g/t | 2.3 – 2.9 | 2.6 – 3.0 | 2.3 – 3.0 | ||||
Cut-off for mill feed open pit | g/t | 0.4 | 0.5 | 0.55 – 0.95 | ||||
Mining recovery factor (underground) | % | 90 – 97 | 90 – 95 | 90 – 95 | ||||
Mining recovery factor (open pit) | % | 97 – 98 | 95 – 98 | 95 – 98 | ||||
Strip ratio (waste:ore) | ratio | 6.2 | 6.6 | 9.3 | ||||
MCF | % | 100 | 100 | 100 | ||||
Dilution open pit | % | 15 – 50 | 2 – 49 | 20 – 40 | ||||
Dilution underground | % | 12 – 25 | 15 – 25 | 5 – 40 | ||||
Plant recovery factor | % | 69 – 96 | 78 – 94 | 79 – 94 | ||||
Processing capacity | Mtpa | 4.7 | 4.7 | 4.7 |
Grade tonnage curves for the underground and open pit Mineral Resource.
Grade tonnage curve - Surface | Grade tonnage curve - Underground | |
Mineral Reserves
Mineral Reserves at St Ives decreased, post mining depletion, by 10% to 1.57Moz in 2017. The dominant contributors to Mineral Reserves are the Invincible open pit, Invincible underground, Invincible South and Hamlet mines. This is reflective of the cyclical nature of exploration discovery and conversion to Reserves in orogenic style WA terrains and the 2017 increase in resources of 17% to 3.85Moz will provide numerous opportunities for increased conversion to Reserves in 2018.
The elevated levels of investment in exploration in 2015, 2016 and 2017 are planned to be repeated in 2018.The expectation is to advance highly ranked projects through development stage gates to deliver the new generation of mines at St Ives to replace the current mining centres. The uncertainty around the timing of discoveries and inherent lead times to bring a new mine into production are characteristic of orogenic-style operations but property endowment and a robust project pipeline continues to justify expenditure and future return on investment. The Mineral Reserves are derived from the LoM plan, which is supported by a detailed design and schedule that takes account of cut-off grades, mining fleet productivities, prevailing geotechnical factors directing optimal sequencing and incorporates appropriate modifying factors. Surface sources include stockpiles. Capital requirements are accommodated in the cash-flow model to ensure sustainable operations over the LoM.
Mineral Reserve classification
Tonnes (kt) | Grade (g/t) | Gold (koz) | ||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Classification | Dec 2017 | Dec 2016 | Dec 2015 | Dec 2017 | Dec 2016 | Dec 2015 | Dec 2017 | Dec 2016 | Dec 2015 | |||||||||||
Open pit and underground | ||||||||||||||||||||
Proved | 1,131 | 2,797 | 1,067 | 3.08 | 2.15 | 3.45 | 112 | 193 | 118 | |||||||||||
Probable | 14,831 | 15,398 | 13,570 | 2.76 | 2.91 | 3.08 | 1,318 | 1,441 | 1,343 | |||||||||||
Total open pit and underground | 15,961 | 18,195 | 14,636 | 2.79 | 2.79 | 3.11 | 1,430 | 1,634 | 1,461 | |||||||||||
Surface | ||||||||||||||||||||
Proved | 3,457 | 3,317 | 2,967 | 1.25 | 1.00 | 0.85 | 139 | 107 | 81 | |||||||||||
Total surface | 3,457 | 3,317 | 2,967 | 1.25 | 1.00 | 0.85 | 139 | 107 | 81 | |||||||||||
Grand total | 19,419 | 21,512 | 17,604 | 2.51 | 2.52 | 2.72 | 1,568 | 1,740 | 1,542 |
Mineral Reserve classification per mining area
Proved | Probable | Total Mineral Reserve | ||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Tonnes (kt) | Grade (g/t) | Gold (koz) | Tonnes (kt) | Grade (g/t) | Gold (koz) | Tonnes (kt) | Grade (g/t) | Gold (koz) | ||||||||||||
Open pit | ||||||||||||||||||||
Incredible | – | – | – | 1,410 | 1.27 | 57 | 1,410 | 1.27 | 57 | |||||||||||
Invincible Pit | 701 | 2.46 | 56 | 1,475 | 2.98 | 141 | 2,176 | 2.81 | 197 | |||||||||||
Neptune | 227 | 3.15 | 23 | 4,049 | 1.93 | 252 | 4,276 | 2.00 | 275 | |||||||||||
Pistol Club | – | – | – | 614 | 2.60 | 51 | 614 | 2.60 | 51 | |||||||||||
Santa Ana | – | – | – | 1,656 | 1.46 | 78 | 1,656 | 1.46 | 78 | |||||||||||
Other | 7 | 1.78 | – | 2,133 | 2.31 | 158 | 2,140 | 2.31 | 159 | |||||||||||
Total open-cut | 935 | 2.63 | 79 | 11,338 | 2.02 | 738 | 12,273 | 2.07 | 817 | |||||||||||
Underground | ||||||||||||||||||||
Cave Rocks | 80 | 4.58 | 12 | 58 | 4.03 | 7 | 138 | 4.35 | 19 | |||||||||||
Hamlet | 116 | 5.74 | 21 | 447 | 3.55 | 51 | 563 | 4.00 | 72 | |||||||||||
Invincible UG | – | – | – | 1,685 | 4.80 | 260 | 1,685 | 4.80 | 260 | |||||||||||
Invincible South | – | – | – | 1,303 | 6.23 | 261 | 1,303 | 6.23 | 261 | |||||||||||
Total underground | 196 | 5.26 | 33 | 3,494 | 5.16 | 580 | 3,689 | 5.17 | 613 | |||||||||||
Surface | ||||||||||||||||||||
Surface stockpiles | 3,457 | 1.25 | 139 | – | – | – | 3,457 | 1.25 | 139 | |||||||||||
Grand total | 4,588 | 1.70 | 251 | 14,831 | 2.76 | 1,318 | 19,419 | 2.51 | 1,568 |
Mineral Resource and Mineral Reserve reconciliation year-on-year
Factors that affected Mineral Resource reconciliation year-on-year | Factors that affected Mineral Reserve reconciliation year-on-year | |
---|---|---|
Mining depletion. |
Mining depletion. |
|
Reduced costs positively impacted Sirius, North Orchin, Cave Rocks and Invincible UG. Revised resource modelling improved economics for Incredible. |
Increased focus on metallurgical recoveries resulted in minor increases in some deposits. |
|
Discovery at Invincible Pit, Invincible UG, Invincible South, APN, and Justice. |
Discovery and conversion at Invincible Pit, Invincible South, Justice and Hamlet. |
Mineral Resource reconciliation (Gold – koz) | Mineral Reserve reconciliation (Gold – koz) | |
Mineral Reserve sensitivity
To illustrate the impact of fluctuations in gold price and exchange rates on the current declaration, St Ives has generated sensitivities with respect to Mineral Reserves. The following graph indicates the Managed Mineral Reserve sensitivity at -15%, -10%, -5%, base (A$1,600/oz), +5%, +10% and +15% to the gold price.
These sensitivities (other than for the base case) are not supported by detailed plans and depletion schedules. They should only be considered on an indicative basis, specifically as such sensitivities assume 100% selectivity, without any operating cost increases.
Mineral Reserve sensitivity (Gold – Moz) | |