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Kalgold openpit mine, South Africa

16th March 2018

By: Thabi Shomolekae

Creamer Media Senior Writer

     

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Name: Kalgold openpit mine.

Location: Kalgold openpit mine is located on the Kraaipan greenstone belt, about 55 km south-west of Mahikeng in the North West, South Africa.

Holding and Controlling Company: Harmony Gold Mining.

Brief Description: The Kalgold openpit mine is surrounded by farm land. The mine accesses gold-bearing ore in a banded ironstone formation in a shear zone within the Kraaipan greenstone belt and has the Kalgold carbon-in-leach (CIL) plant on site.

The A-Zone pit, currently the only active pit, includes the former Watertank pit.

Brief History: Shell Minerals Division started exploration of the Kraaipan greenstone belt in 1980.

The D-Zone one area was discovered on the Goldridge farm in 1991.

West Rand Cons Exploration acquired the orebody in 1994 and started mining in December 1995.

Ore was treated by heap leaching until the installation of the first two mills in 1997.

Harmony acquired the mine in July 1999. A third mill was added in 2003 to increase treatment capacity and in November, the group entered into an agreement to sell the mine to Afrikander Lease. However, the contractual obligations were not met and subsequently the agreement was cancelled in March 2004.

The D-Zone pit was mined out in 2009.

Products: Gold.

Geology/Mineralisation: Gold mineralisation is hosted by steeply dipping banded iron formations interbedded with schist, shale and greywacke. Banded iron formations consist of rhythmically banded chemical sediments comprising alternating light and dark laminae, which vary from 10 mm to 50 mm in thickness.

The banded iron formations are oxidised to about 40 m to 60 m below surface. Near surface the material is red and porous, comprising quartz, hematite and goethite with minor magnetite. At depth, the unaltered banded iron formation consists of quartz, siderite, pyrite, pyrrhotite and magnetite with minor chlorite, calcite and stilpnomelane. In general, gold mineralisation has an erratic and localised distribution. Individual gold grains are on average less than 10 μm and occur in clusters. Gold is generally associated with goethite in the weathered rocks, with pyrite and pyrrhotite in the fresh material.

Geological modelling has been completed using Datamine software. Drill holes and blastholes have been surveyed and used to build a series of west–east sections from north–south through the various pit areas. The A-Zone and Watertank areas have been modelled as a single contiguous area as the geology and data is continuous and contiguous.

A wireframe geological model has been built by linking individual sections to form a continuous wireframe model. The construction of the sections includes outlines for the mineralised and waste zones. The definition of the mineralised zones is based primarily on the lithological contacts between the banded iron formations and waste material (volcanic/sedimentary schists).

The geological model is constructed in the form of a wire frame from exploration borehole intersections, blasthole information and geological mapping within the pit and is updated regularly as new information becomes available.

Reserves: Total proved and probable reserves as at June 30, 2017, were estimated at 26.6-million tonnes grading 1.9 g/t gold.

Resources: Total measured, indicated and inferred mineral resources for Target 1 as at June 30, 2017, were estimated at 65.4-million tonnes grading 0.7 g/t gold.

Mining Method: Openpit.

Major Infrastructure and Equipment: The Kalgold plant receives ore from the pit at about 129 000 t/m. The ore has an average moisture content of about 1%.

Ore is transported from the pit by truck and tipped into the plant run-of-mine pad. The ore is then fed into the preprimary crusher for the first stage of comminution. Preprimary product is transported to the primary crusher before going through the final stage in the secondary and tertiary crushers. Tertiary crusher product is temporarily stored in the dome prior to milling.

The ore is fed from the dome to the A, B and C ball mills. The identical A and B mills are generally fed at 55 t/h. The C mill is the biggest with throughput of 105 t/h to 110 t/h. The mill product ranges from 75% to 80% passing 75 μm.

Lime and flocculant are the two main components of the thickening process.

The thickener underflow, which normally ranges from 50% to 55%, is conveyed to the pre-aeration tank for precondition before the addition of the cyanide. The preconditioning is performed to render cynocides less reactive to cyanide. Cyanide is automatically added to either Leach 2 or Leach 3, depending on the degree of the pre-aeration stage.

The dissolved gold, still in pulp, is transferred to the CIL circuit where activated carbon is added to adsorb the gold in solution. The CIL tanks are fitted with rotary screens to allow movement of the carbon in a counter-current manner with the slurry.

The Kalgold plant uses the Zadra elution process for gold recovery. Carbon is treated with a hot caustic and cyanide solution. The pregnant solution is pumped into the electrowinning circuit for gold recovery.

Prospects: For the Kalgold mining lease area a drill proposal comprising 67 holes, ~19,350 m has been finalised and approved for completion in the first half of the 2018 financial year. Follow-up drilling will be planned based on these results.

Contact: Harmony investor relations manager Lauren Fourie

Contact Details:
Harmony
Cell +27 71 607 1498
Tel +27 71 607 1813
Email Lauren.Fourie@Harmony.co.za
Website https://www.harmony.co.za/our-business/our-operations/tshepong

Edited by Sheila Barradas
Creamer Media Research Coordinator & Senior Deputy Editor

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