The high-grade manganese ores (>42 wt % Mn) in the northwestern portion of the Kalahari Manganese Field (Wessels, Black Reck and the N'chwaning Mines) consist of braunite II , bixbyite, hausmannite, hematite, calcite and andradite, with trace amounts of braunite. In contrast to this, the low-grade (diagenetic to very low grade metamorphic) Mamatwan-type ores to the southeast consist mainly of braunite, hausmannite, jacobsite, hematite, kutnahorite and calcite

Mineralisation of the Kalahari Manganese field is developed in three braunite-kutnahorite lutite layers interbedded with iron formation in the Hotazel Formation of the Palaeoproterozoic (2400 to 2100 Ma) Transvaal Sequence which was deposited within an intracratonic basin on the Kaapvaal Craton. The relatively flat lying, concealed, mineralised, Hotazel Formation units of the Kalahari manganese field covers an area of some 30 x 10 km.

The base of the Hotazel Formation consists of a bright-red banded iron formation bed (varying from massive to fine-grained specularite and/or euhedral magnetite cystals) overlying volcanic glass breccias and lavas of the Ongeluk Formation. The banded iron-formation units grade into microcrystaline kutnohoritic ovoidrich braunite rock. The kutnohorite in this area is concentrated in ovoids, which represent partially compacted, early diagenetic concreations in hematite and braunite rock. The braunite rock bed of the lower section of the lowest of the three sedimentary cycles present in the Hotazel Formation, is between 5 and 45m thick. This is the major ore unit of the Kalahari manganese field with a manganese content varying between 20 and 48 weight percent. The middle manganese-bearing unit (cycle 2) is a maximum of 2m thick and in not economically viable. The top manganese ore body was mined in previous years. It rarely exceeds 5m thickness. Grey hematitic and manganese minnesotaite rocks are found between the lower and the middle maganese ore bodies.

Mamatwantype ore is the major manganese ore in the Kalahari basin. It is primary a diagenetic to low-grade metamorphic ore, consisting of braunitic matrix and abundant primary carbonates and ovoids of kutnohorite. Minor minerals also include hausmannite, cryptomelane, jacobsite and hematite. The Mamatwan mine exploits the lower most of the three layers which averages 45 m in thickness. This layer has been subdivided into: (1) an upper 19.5 m thick sub-economic layer with >30% Mn and an Mn:Fe ratio of 3, (2) a central 19.7m thick economic layer with 38% Mn and an Mn:Fe ratio of >8, and (3) a lower 6 m thick subeconomic layer with 30% Mn and an Mn:Fe ratio of 5.

The Wessels Mine is seperated into three underground areas. The first, the central-southern area, is particularly rich in carbonates, primarily manganoan calcite, kutnahorite and rarely rhodochrosite. The second, the north-western area, in known for its sturmanite, gaudefroyite and sugilite. Finally the third area, the central eastern area, has sugilite, andradite, inesite, hydroxyapophyllite, ruizite, barite and celestine.

The Hotazel Manganese Mines (HMM) has two operations, the Wessels high-grade underground mine and the Mamatwan medium grade open-pit mine.

Mamatwan Mine is a conventional opencast operation in that the overburden is removed to uncover the manganese orebody using a truck and shovel fleet. The orebody is then drilled and blasted. Capacity of approximately 3.5 Mtpa ROM (100 per cent basis).

Wessels is an underground bord and pillar operation with a current capacity of approximately 1.2 Mtpa of ROM production (100 per cent basis).

Mamatwan.
Mined ore is processed into a saleable product through a crushing and wet screening operation, with some ore undergoing further processing by dense media separation and sintering. During beneficiation, the average grade of ore is increased from approximately 37 per cent Mn to approximately 46 per cent Mn.

Wessels.
Primary crushing of ore takes place underground, while secondary crushing forms part of the surface operations. ROM ore is washed and screened on the surface to produce various quality products.