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Impala / Mineral resource and mineral reserve statement
 

Mineral resources and mineral reserves
/ Impala /

 Impala
 
Impala mineral resources and mineralreserves

The Impala mining operation is located just to the north of Rustenburg on the western limb of the Bushveld Complex. The location of the Impala operation showing the adjacent mines is shown in the accompanying locality map. Impala, together with the joint venture with the RBR, holds contiguous mining and prospecting rights over a total area of 33 534ha across 20 farms or portions of farms.


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Both the Merensky and UG2 Reefs are exploited. The Merensky Reef is generally composed of an upper feldspathic pyroxenite, overlying a thin basal chromitite stringer, followed by an anorthosite to norite footwall. Locally this is termed a “pyroxenite reef”. Occasionally a pegmatoidal pyroxenite and a second chromitite stringer may be developed between the feldspathic pyroxenite andthe footwall units. This is termed a “pegmatoid reef”. As an aid to mining operations the Merensky Reef is further defined as being “A”, “B” or “C” Reef if it rests on specific footwall units, ie locally called Footwall 1, 2 and3 respectively.

The UG2 Reef is defined as a main chromitite layer, with most of the mineralisation confined to this unit, followed by a poorly mineralised pegmatoidal pyroxenite footwall. The hangingwall to the main chromitite layer is a feldspathic pyroxenite containing up to four thin weakly mineralised chromitite layers.

Both mineralised horizons dip gently away from the sub-outcrop in a north-easterly direction at 10° to 12°. The vertical separation between the Merensky and UG2 Reefs varies from about 125m in the south to 45m in the north of the mining area. The reefs may be disrupted by minor and major faults, lamprophyre and dolerite dykes, late stage ultramafic replacement pegmatoid bodies and potholes. The latter features are generally circular in shape and represent “erosion” or “slumping” into the footwall units. They vary in size from a few metres to tens of metres across and up to tens of metres in depth. All the abovementioned features contribute to dilution of the mineralised horizons and are accounted for in the mineral resource and mineral reserve statements as geological losses.

The Merensky and UG2 Reefs are mined concurrently; the mining method is predominantly conventional breast mining. Mechanised (trackless) bord and pillar mining occurs in selected Merensky Reef areas on two of the shafts (12 and 14 Shafts). Some small-scale opencast mining was undertaken at the outcrop positions to a maximum depth of 50m. This was terminated in the past year as the available areas were mined out. Stoping at the operations is carried out through conventional double-sided breast mining in accordance with Impala’s best practice principles. The haulages are developed in opposite directions from cross-cuts connected to a central shaft position, following the two reef horizons on strike in the footwall and are defined as half levels. Footwall drives are developed at approximately 18m to 20m below the reef horizon with on-reef raise/winze connections being between 180m and 250m apart. Panel face lengths vary from 15m to 30m forboth Merensky and UG2 Reefs, with panels being typically separated by 6 x 3m grid pillars with 2m ventilation holings. Stoping widths are approximately 1.2mand 1.0m for conventional Merensky and UG2 Reefs respectively, depending on the width of the economical reef horizon. The average stoping width of mechanised panels is about 1.9m.

 

Mine design and scheduling of operational shafts is undertaken utilising CadsMine™ software, while the mine design and scheduling for projects are done using Mine 2-4D™ software. Geological models/ore blocks are updated and validated using G-Blocks and boundaries in the MRM information system. Grade block models are developed utilising Isatis™ software. The mine design for the first five years is monthly per crew. This is extended on an annual basis for the remaining period of the LoM. Key modifying factors such as overbreak, underbreak, off-reef mining, development dimensions, sweepings and mine call factors are applied to the mining area (centare profile) to generate tonnage and grade profiles. The planning sequence is currently under review.


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The shafts at Impala are locally divided into three groupings, the so-called Old Men (4, 6, 7, 7A, 8, 9 and E/F), the Big5 (1, 10, 11, 12 and 14) and the Triple Build-up (16, 17 and 20). The distribution of the reserves is depicted in the accompanying graph; it is clear that the bulk of the reserves (53%) is located in the Triple Build-up project shafts.

The 30-year LoM profile for Impala is depicted in the graph that follows. LoM I comprises the profiles of 14 operating vertical shafts, five associated with declines and three approved project shafts (16, 17 and 20) under construction and/or ramp-up. The 20 Shaft UG2 Reef and the extension of 20 Shaft Merensky Reef to 26 and 27 Levels constitute LoM II. LoM III is made up of potential future shaft blocks currently in different stages of project studies. This profile is based on current assumptions and may change in future. Note in particular that the profile has been adjusted from the previous outlook given a number of considerations, such as funding for new shafts like 18 Shaft which has been deferred. Medium-term production plans have been moderated in view of current productivity levels.

 
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Impala mineral resources and mineral reserves (100%)
as at 30 June 2013
  Mineral resources   as at 30 June 2013   as at 30 June 2012  
  Orebody   Category   Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
6E  
Moz  
Pt  
Moz  
Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
Pt  
Moz  
  Merensky   Measured   145.8   117   6.62   7.39   31.0   34.6   19.6   153.7   125   5.90   6.59   29.2   18.5  
Indicated   84.8   112   6.29   7.03   17.2   19.2   10.8   87.0   107   6.15   6.86   17.2   10.9  
Inferred   68.4   125   5.50   6.14   12.1   13.5   7.6   65.2   130   5.46   6.09   11.4   7.2  
  UG2   Measured   134.1   63   7.31   8.76   31.5   37.8   18.3   135.9   64   7.32   8.80   32.0   18.6  
Indicated   68.1   64   7.26   8.71   15.9   19.1   9.2   68.3   63   7.22   8.67   15.9   9.2  
Inferred   34.1   66   7.44   8.92   8.2   9.8   4.7   33.3   63   7.40   8.89   7.9   4.6  
    Total   535.3     6.73   7.78   115.8   133.9   70.3   543.4     6.50   7.53   113.6   68.9  
                                
  Mineral resources   as at 30 June 2013   as at 30 June 2012  
  Orebody   Category   Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
6E  
Moz  
Pt  
Moz  
Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
Pt  
Moz  
  Merensky   Proved   9.5   133   3.91   4.36   1.2   1.3   0.8   10.9   129   4.10   4.57   1.4   0.9  
Probable   111.1   127   4.34   4.85   15.5   17.3   9.8   113.2   131   4.25   4.74   15.5   9.8  
  UG2   Proved   13.6   105   3.75   4.50   1.6   2.0   1.0   15.9   98   4.07   4.89   2.1   1.2  
Probable   117.9   105   3.75   4.50   14.2   17.0   8.2   123.2   99   3.87   4.65   15.3   8.9  
    Total   252.1     4.02   4.65   32.6   37.7   19.8   263.3     4.05   4.70   34.3   20.8  
  
  Mineral resources     as at 30 June 2013   as at 30 June 2012  
  Orebody   Category   Tonnes  
Mt  
Pt  
grade  
g/t  
Pt  
Moz  
Tonnes  
Mt  
Pt  
grade  
g/t  
Pt  
Moz  
  1 and 2 Tailings Complex   Indicated   48.1   0.42   0.6   48.1   0.42   0.6  

Impala/RBR JV
  Mineral resources   as at 30 June 2013   as at 30 June 2012  
  Orebody   Category   Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
6E  
Moz  
Pt  
Moz  
Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
Pt  
Moz  
  Merensky   Measured   5.3   154   6.39   7.13   1.1   1.2   0.7   5.3   152   6.52   7.28   1.1   0.7  
Indicated   8.4   151   6.97   7.78   1.9   2.1   1.2   7.0   150   6.84   7.64   1.5   1.0  
Inferred   28.3   131   5.64   6.30   5.1   5.7   3.2   23.4   122   6.51   7.27   4.9   3.1  
  UG2   Measured   1.5   53   7.45   8.94   0.4   0.4   0.2   2.3   53   7.49   9.00   0.6   0.3  
Indicated   3.2   54   7.85   9.41   0.8   1.0   0.5   1.8   54   7.86   9.44   0.5   0.3  
Inferred   9.5   58   7.49   8.99   2.3   2.8   1.3   8.6   57   7.43   8.93   2.1   1.2  
    Total   56.3     6.40   7.31   11.6   13.2   7.1   48.5     6.82   7.78   10.6   6.6  
 
Comparison between mineral resource estimate for UG2 chromitite layer and the estimate for the UG2 minimum mining width
   Minimum mining width UG2 chromitite layer
  Mineral resources   as at 30 June 2013 as at 30 June 2013
  Orebody   Category   Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
6E  
Moz  
Pt  
Moz  
Tonnes  
Mt  
Width  
cm  
4E  
grade  
g/t  
6E  
grade  
g/t  
4E  
Moz  
6E  
Moz  
Pt  
Moz  
  UG2   Measured   191.2   95   5.50   6.59   33.8   40.5   19.6   134.1   63   7.31   8.76   31.5   37.8   18.3  
Indicated   95.5   95   5.47   6.57   16.8   20.2   9.8   68.1   64   7.26   8.71   15.9   19.1   9.2  
Inferred   46.2   95   5.90   7.08   8.8   10.5   5.1   34.1   66   7.44   8.92   8.2   9.8   4.7  
    Total   333.0     4.81   5.78   59.4   71.2   34.5   236.3     7.31   8.77   55.6   66.6   32.2  

Relationship between exploration results, mineral resources and mineral reserves (100%)

Notes
  • Mineral resources are quoted inclusive of mineral reserves
  • Mineral resource estimates allow for estimated geological losses but not for anticipated pillar losses during eventual mining
  • The modifying factors used to convert a mineral resource to a mineral reserve are derived from historical performance using an in-house ore accounting system. This system is able to provide dilution factors that are applied to in situ estimates to project the final product delivered to the mill
  • Mineral reserves quoted reflect the grade delivered to the mill
  • The year-on-year reduction in proved Merensky mineral reserves illustrates that main development remains a focus area
  • The quantum of proved Merensky Reef mineral reserves at Impala remains low at some 20% below the same for the UG2 Reef
  • The UG2 mineral reserve widths show an increase from last year due to additional allowance for a new support standard (netting and bolting)
  • The increase in the mineral resource of the joint venture area relates to remodelling of additional data both in the block as well as surrounding area
  • The UG2 mineral resources estimate is compared with a minimum mining cut of 95cm. This illustrates the significant dilution as very little metal is added by the increase to the mining width
  • Mineral resources and mineral reserve grades are shown for both 4E and 6E. The 4E grade was recalculated from 6E to represent the summation of individual Pt, Pd, Rh and Au grades
  • The mineral resources and mineral reserves involved with the royalty agreement with the RBPlat are excluded in this report as the ownership vests with the RBPlat. This refers to the agreement with the RBPlat to access certain of its mining areas at Bafokeng Rasimone Platinum Mine (BRPM) from 6, 8 and 20 Shafts
  • Rounding of numbers may result in minor computational discrepancies; mineral resource estimates are inherently imprecise in nature; the results tabulated in this report must be read as estimates and not as calculations; inferred mineral resources in particular are qualified as approximations.

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