Mimosa is wholly owned by Mimosa Investments Limited, a Mauritius-based company jointly held by Implats and Aquarius Platinum Limited (Aquarius) in a 50:50 joint-venture. It is located on the Wedza Geological Complex on the Zimbabwean Great Dyke east of Bulawayo. In FY2009 the operation produced 91 500 ounces of platinum in concentrate. The operation comprises a shallow underground mine accessed by a decline shaft, and a concentrator.

History

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 by 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.

Geology

Although platinum was first discovered in the Great Dyke in 1918, its exploration was overshadowed by that of the Bushveld Complex in South Africa. Focus has returned to the Great Dyke in recent years, following the increase in demand for platinum and given that much of the shallow mineral resources in the Bushveld Complex are spoken for.

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), 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 complexes 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, directly below the mafic-ultramafic contact, which in turn hosts the economic PGM-bearing Main Sulfphide Zone (MSZ). The MSZ is a continuous layer between 2 and 10 metres thick that forms an elongated basin. Optimal mineralisation varies and, in contrast to the Bushveld Complex, is often difficult to follow visually. Peak values for the PGM and base metals are commonly offset, while the proportions between platinum and palladium also vary vertically.

The Mimosa lease encompasses four areas namely North Hill, South Hill, Mtshingwe Block and Far South Hill. These areas covering some 6,590 hectares, are separated by major faults. Unlike much of the Great Dyke, Mimosa has a well-defined grade profile with an identifiable reef horizon marker facilitating grade control.

Note: Mineral Resources are quoted inclusive of Ore Reserves. See Implats’ Mineral Resource and Mineral Reserve Statement 2009 (PDF - 3.5MB) for full details.

Mining

The orebody is extremely shallow and mining commences at a depth of 60 metres below surface and currently extends to a depth of approximately 200 metres. The bord and pillar mining method is employed and stoping widths average around 2 metres. Mimosa is a fully mechanised mining operation.

Metallurgy

Mimosa has a concentrator plant on site, where initial processing is done. The Wedza Phase 5 expansion project focusing on the extension of milling and tailings handling capacities has been completed. As a result the extra floatation capacity created in Phase 4 can now be fully optimised resulting in a 21% increase in the tonnes milled by the facility. Consequently production increased by 19% in FY2009. 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).

Indigenisation

Zimbabwe passed a bill covering local ownership of foreign-owned firms at the end of September 2007. The indigenisation levels required are set at 51%. The business is currently reviewing options in this regard.

Sustainable development

Mimosa is 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.