Mineral Resources and Mineral Reserves
Mimosa

Mimosa is located 20km west of the town of Zvishavane, 150km east of Bulawayo on the Wedza Complex of the Great Dyke in Zimbabwe. 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 and increased this stake 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. Mimosa is wholly owned by Mimosa Investments Limited, a Mauritius-based company jointly held by Implats and Aquarius in a 50:50 joint venture.

The Government of Zimbabwe has been pursuing the greater participation in the mining sector by indigenous Zimbabweans. Implats is continuing to engage with the Government of Zimbabwe (through the Ministry of Youth Development, Indigenisation and Empowerment) with respect to agreeing plans for the indigenisation of Zimplats and Mimosa. The current position with regard to the implementation of the Government of Zimbabwe’s indigenisation plans is not clear and depending on what position is ultimately taken by the Government of Zimbabwe, Implats’ attributable mineral resources and mineral reserves may be significantly reduced.

PGM mineralisation at Mimosa is located in four erosionally isolated and fault-bounded blocks, consisting from north to south of the North Hill orebody, South Hill orebody, Mtshingwe Block orebody and Far South Hill orebody areas. Mimosa holds contiguous mining rights over the above mentioned areas totalling 6 591ha. The indigenisation plan has not been completed and the reported attributable mineral resources and mineral reserves are still at the same attributable ownership level of 50%.

The platinum-bearing Main Sulphide Zone (MSZ) is located in the P1 pyroxenite some 10m below the ultramafic/mafic contact. The MSZ is a continuous layer, 2m to 3m thick, and forms an elongated basin. The zone strikes in a north-northeasterly trend and dips at about 10° on the margins flattening towards the axis of the basin. The MSZ at Mimosa has a well-defined grade profile where peak base metal and PGM values are offset vertically, with palladium dominant towards the base, platinum in the centre and nickel towards the top. At Mimosa the MSZ is visually identified using pyroxene and sulphide mineralisation followed by confirmatory channel sampling unlike at Zimplats, where the MSZ is difficult to identify visually with no clear marker horizons, and systematic monitoring supported by channel sampling is required to guide mining. Minor faults and dykes are present at Mimosa. Although no potholes have been identified, low-grade areas and areas of no mineralisation or “washouts” have been intersected. These are all accounted for in the mineral resource and mineral reserve statement. Mimosa is a shallow underground mine accessed by the Blore Decline Shaft system. The bord and pillar mining method is employed and stoping widths average around 2m. Mining bords advance along 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.

Optimum stoping widths and mining cut selection are regularly reviewed given variation in metal prices and the non-linear distribution on the different metals. Mining models are defined relative to the platinum peak and recent work confirmed that a 2m slice is presently the optimum cut. The mineral resources and mineral reserves listed below are based on a slice that extends from 0.45m above the platinum peak datum to 1.55m below the datum. The reported mined grade is based on inverse distance block modelling of borehole values using Surpac^TM. Mine design and scheduling is done utilising Surpac^TM. The mine plan is derived from a target milling throughput. Strategic stockpile levels are factored into the volumes to be hoisted. Losses due to mining and geology are applied to the planned tonnages and then consolidated into the LoM profile. The assured LoM of Mimosa is limited to the northern part of the South Hill deposit known as the Wedza shaft area; however, the LoM depicted below now includes on-reef stoping from the Wedza shaft mineral reserve area into the southern part of the South Hill orebody known as the Mtshingwe area.

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 an offtake agreement with IRS.