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Great Dyke in Zimbabwe

Mimosa

Mimosa is jointly held by Implats and Aquarius. Its operations are located on the Wedza Geological Complex on the Zimbabwean Great Dyke, 150 kilometres east of Bulawayo. The operation comprises a shallow underground mine, accessed by a decline shaft, and a concentrator.

Operational review 2015

 

Business summary

  • Joint venture with Aquarius Platinum Limited
  • Mechanised shallow underground mine
  • Concentrator plant
  • Reserves: 1.0 million attributable ounces of platinum
  • Resources (including reserves) 3.7 million attributable ounces of platinum
  • Production: 117 400 ounces of platinum inconcentrate
  • Employees and contractors: 1 402
 

The Great Dyke is a layered complex similar to that of the Bushveld Complex. It extends for 550 kilometres and has a maximum width of 11 kilometres. Within the Great Dyke four geological complexes are known to contain PGM and base metal deposits. These are the Wedza Complex (Mimosa – Aquarius and Implats), the Selukwe Complex (Unki – Anglo Platinum), the Hartley Geological Complex (Hartley and Ngezi Platinum Mines – Zimplats) and the Musengezi Complex. The Hartley Geological complex is the largest of the PGM bearing complex’s containing 80% of the known PGM resources in Zimbabwe.

The stratigraphy is broadly divided between a lower ultramafic and an overlying mafic sequence. The ultramafic sequence hosts the P1 pyroxenite, which in turn hosts the economic PGM-bearing Main Sulphide Zone (MSZ). The MSZ is a continuous layer generally between 2 to 3 metres thick. Optimal mineralisation varies.

Mimosa has a well-defined grade profile where peak base metal and PGM values are offset vertically, with palladium dominant at the base, platinum in the centre, and nickel towards the top. Visual identification of the MSZ is difficult.

Mimosa holds contiguous mining rights over 6 591 hectares on the North Hill, the South Hill, Mtshingwe Block and Far South Hill orebody areas. The orebody is shallow and mining commences at a depth of 150 metres below the surface and extends to a depth of approximately 200 metres. The bord and pillar mining method is employed and stoping widths average around 2 metres. Mining bords advance along the strike.

The mining cycle involves mechanised support drilling and installation, mechanised face drilling, charging and blasting, and mechanised lashing onto a conveyor network to an underground bunker. From the bunker ore is conveyed out to a surface stockpile.

It is expected that steady-state platinum in concentrate production will be maintained at around 100 000 ounces per annum. A detailed feasibility study to evaluate the potential to increase production will be completed early in 2016

 

Mimosa has a concentrator plant on site where initial processing is done.  Concentrate is transported by road to Impala Platinum’s Mineral Processes in Rustenburg in terms of a life-of-mine offtake agreement with Impala Refining Services (IRS). The mine is in discussions with other platinum producers to co-fund a smelter and studies are currently under way in this regard.

 

Mimosa remains committed to social development initiatives and engages in, develops and builds community relationships. It takes responsibility for economic, social and environmental issues that impact its people, communities and environments and is involved in a number of community projects in the area.

 

The Government of Zimbabwe has been pursuing greater participation in the mining sector by indigenous Zimbabweans. The company continues to engage with the government with respect to agreeing plans in this regard.

 

Mimosa was acquired by Zimasco from Union Carbide in 1993. Zimasco piloted platinum mining in Zimbabwe by resuscitating the operation and steadily increasing production to 1,000 tonnes per day achieved in 1998. In July 2001, Implats acquired a 35% stake in Mimosa for a consideration of R246 million. This stake was increased to 50% with a further acquisition of 15% in August of the following year. Aquarius acquired a 50% stake in Mimosa during the same year.

Production     2015   2014   2013   2012   2011  
  Tonnes milled ex mine   ('000t)  2 586   2 453   2 381   2 324   2 311  
  Headgrade (6E)  (g/t)  3.93   3.92   3.95   3.93   3.91  
  Platinum in concentrate   ('000oz)  117.4   110.2   100.3   106.0   104.9  
  PGM in concentrate   ('000oz)  250.1   234.6   214.8   222.8   219.7  
                
Labour efficiency              
  Tonnes milled per employee costed**   (t/man/annum)  1 819   1 500   1 372   1 381   1 319  
               
Cost              
Mining cost of sales   (Rm)  (2 640)  (2 398)  (1 956)  (1 498)  (1 229) 
  Mining operations   (Rm)  (1 375)  (1 425)  (1 110)  (813)  (730) 
  Processing operations   (Rm)  (501)  (375)  (311)  (242)  (196) 
  Other   (Rm)  (764)  (598)  (535)  (443)  (303) 
               
Total cost   (Rm)  2 043   1 958   1576   1193   1 016  
               
Unit costs              
  per tonne milled   (R/t)  790   798   662   513   440  
    (US$/t)  69   77   75   66   63  
  per platinum ounce in concentrate (R/oz)  17 402   17 768   15 713   11 255   9 685  
    (US$/oz)  1 525   1 713   1 782   1 453   1 377  
               
Financial ratios              
  Gross margin ex mine   (%)  22.9   19.3   24.2   37.7   52.2  
               
Capital expenditure              
    (Rm)  343   298   265   497   372  
    (US$m)  30   29   30   64   53  
               
Safety              
  LTIFR     (pmmhwǂ 0.13   0.38   0.26   1.19   0.20  
  FIFR      (pmmhwǂ 0.000   0.000   0.000   0.000   0.000  
               
Labour complement              
  Own employees   (no)  1 394   1 422   1 552   1 572   1 567  
  Contractors   (no)  8   128   130   199   229  
  **Total employees excluding capital project employees  
  ǂPer million man hours worked