Mimosa is located on the Wedza Geological Complex on the Zimbabwean Great Dyke 20 kilometres west of the town of Zvishavane, 150 kilometres east of Bulawayo.

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 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, 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 3 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.

Mimosa is a shallow underground mine accessed by the two incline shafts, the Wedza Decline and Blore Shaft. The bord and pillar mining method is used to extract ore over average stoping widths of around 2m. The bord widths vary from 6m to 15m wide, depending on the ground control district. Minimum pillar sizes are dependent on depth from surface to give an adequate safety factor of greater than 1.6. Pillar sizes are, 10m x 3m above 16 level, 10m x 3.5m from 16 level and below, 10m x 4.5m and 4m x 8m in 6m bords in special areas as determined by the ground control districts. The strike pillars in panels are elongated along strike to cater for the predominant east-west faults and dykes and to avoid shear movement down-dip. Stoping mining bords advance along strike. The mining cycle involves mechanised support drilling and installation, mechanised face drilling, charging and blasting followed by mechanised lashing onto a conveyor network feeding 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 of the different metals. Mining models are defined relative to the platinum peak position within the MSZ. The current mining horizon is a two-metre slice defined by the hangingwall at 0.45m above and the footwall at 1.55m below the Platinum peak position.

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). Mimosa is evaluating various alternatives for the beneficiation of its material within Zimbabwe.