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  

St Ives gold mine

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
Grade tonnage curve - Surface   Grade tonnage curve - Surface
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 classifi cation

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 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)
  Mineral Resource reconciliation (Gold – koz)

St Ives gold mine