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The world chromium ore production originates from the mineral chromite (a chromium-iron oxide) in the rock chromitite. The majority of the chromium ore resources of the world are to be found in the Bushveld Complex of South Africa and the Great Dyke of Zimbabwe, where it occurs as numerous thin stratiform chromitite layers. Although some of the chromitite layers have been known since 1865, limited mining only commenced in 1916 in the Bushveld Complex and in 1919 on the Great Dyke. The use and mining of chromium escalated only after the second world war.

Up to 11 chromitite layers are known in the Great Dyke, named from the top down as Seams 1 to 11. At Zimplats the uppermost chromitite layer (Seam 1) is about 220m below the MSZ. It can therefore not be mined from the existing infrastructure and is mined by other operators and artisanal miners close to surface for its chromium content only.

Twelve layers are known in the Bushveld Complex, which are further clustered into three groups, the Lower, Middle and Upper Groups of chromitite layers. Named from the bottom up, they are termed LG1 to LG7, MG1 to MG4, and the UG1 and UG2. In places, individual chromitite layers may comprise multiple layers of subsidiary chromitite units, separated by intercalated silicate units.

In the Bushveld Complex, only the LG6, MG1 and UG2 chromitite layers are amenable to underground mining. The uppermost chromitite layer (UG2) is between 50 and 400m below the Merensky Reef and hosts economically exploitable quantities of PGMs within the chromitite. The UG2 chromitite layer is therefore mined at all the Implats operations, principally for the PGMs. Chromium can therefore be seen as a by-product of the UG2 Reef in South Africa. The LG6 and MG1, with an average Cr₂O₃ grade of between 40 and 50%, is more than 250m below the UG2. They can therefore not be mined from the existing infrastructure at the Implats operations and are mined by other operators close to surface in opencast and underground mining operations for its chromium content only.

The UG2 Reef at Impala has an average in situ Cr₂O₃ grade of about 33%, and a mined grade of about 16%. The mined ore from the UG2 Reef is milled and processed to recover the PGMs at the mine’s two PGM concentrator plants. The tailings from the central concentrator is pumped directly to the tailings dams, as this is predominantly Merensky Reef tailings. Some of the tailings generated by the UG2 PGM recovery plant is reprocessed at two metallurgical plants to recover the chromite. Impala has an off-take agreement with Merafe Resources and sells 220kt of chromite concentrate recovered at one of the chromite recovery plants. The second chromite recovery plant which is owned by Impala Chrome was commissioned in 2010, and is operated by Chrome Traders (Pty) Ltd. Currently about 230kt per annum of chromite is reprocessed by Chrome Traders and the remainder is pumped to the tailings dams. The retrieved chromite from the UG2 tailings has an average Cr₂O₃ grade of about 42%. The number 3 and number 4 tailings dams at Impala currently contain about 500Mt of milled and processed ore, with an average Cr₂O₃ grade of less than 8%.