South African manganese deposits are currently confined to the Early Proterozoic Transvaal Supergroup, Northern Cape Province. They can be grouped into two major categories:
1. Syngenetic carbonate-rich manganese deposits interbedded with the banded iron formations (BIF) of the Hotazel Formation, colloquially called the Kalahari Manganese Field.
2. Karst-fill type manganiferous material from residual Fe-rich manganese developed in dolomites of the Campbell Rand Subgroup in the Postmasburg Fe-Mn Fields.

The Kalahari Manganese Field is situated within a structural basin, known as the Dimoten Synclinorium, plunging at an angle of 3° to 8° to the north and northwest. It extends from Mamatwan Mine in the south for approximately 40 km to Wessels Mine in the north, with an east-west extent varying between 5 and 15 km.

Local Geology
The manganese mineralisation at Mamatwan is hosted by the Hotazel Formation of the Postmasburg Group (Transvaal Supergroup) and occurs as stratiform bodies interbedded with banded ironstone formation. This Formation is characterized by three manganese-rich horizons, called the Lower, Middle and Upper Bodies respectively, separated by BIF.

The lowermost of the three units, the Lower Body (LB), is the only unit exposed and currently mined at Mamatwan Open Pit Mine. The Middle Body is poorly developed, often ferruginized, and carries no economic value. The Upper Body (UB) is considered to be potentially economic, with manganese scattered throughout the unit. The Kalahari Manganese Field, with specific reference to the Mamatwan type ore (rich in braunite–kutnahorite mineral assemblages) represents approximately 97% of the total manganese resource in the region.

At Mamatwan Mine the LB is 37.5 m thick on average. It is subdivided into an uneconomic 19.5 m thick upper horizon (the Top Cut) containing ±31% Mn, with a Mn/Fe ratio of 5; a central horizon (the Manganese Cut) which is on average 19.7 m thick and contains ±37.5% Mn with a Mn/Fe ratio of 8.5; and a 6 m thick Basal horizon. These are subdivided into smaller seams (Zones), based on different mineralogical compositions. The Zones are visually distinguishable from each other and are identifiable by a combination of geological logging and chemical analysis. The M, C, and N Zones of the central horizon are high grade while the lower grade material of the Top Cut is represented by the V, W, X, Y and Z Zones. The Basal horizon is low grade and not considered to be potentially economic so is not part of the Mineral Resource.

The ore at Mamatwan consists of banded, very fine-grained braunite-kutnahorite lutite, containing concretionary ovoids, laminae and lenticles of Mn-calcite with which hausmannite is commonly associated. Subordinate amounts of hematite, jacobsite and rhodochrosite are also present. The relatively high Mn/Fe ratio of the economic manganese ore makes it suitable for the production of high manganese (76% Mn) alloys. The relatively high carbonate content of the ore, reflected in the CO2 content of 12 to 16%, makes it virtually self-fluxing.

Mamatwan mine consists of an open pit operation that commenced in 1963. This pit is still operational, and is being extended to the north and west. The current run of mine for Mamatwan mine is in the order of 3 million tons per annum. Manganese ore is sold to both the local and international markets.

Stripping and stockpiling of topsoil and waste rock
Mamatwan mine is a conventional opencast operation in that topsoil and waste rock is removed to uncover the manganese ore body using truck and shovel methods. Topsoil is transported via truck to designated topsoil stockpile areas for later use as part of rehabilitation. Waste rock is stripped and transported to one of the designated WRDs at the MMT. Waste rock is either backfilled into the open pit or used to flatten the slopes of existing dumps.

Access to open cast workings
Ore is drilled and blasted, and hauled using front end loaders and shovels to the "in-pit" primary crusher. Crushed ore is conveyed to a product stockpile area (ROM stockpile) near the mineral processing plant. Excess ore is stored and crushed as required.

In pit crushing and screening
Oversize ore is crushed using a “in-pit” jaw crusher to reduce the size of the ore for further downstream processes. The crushed ore is conveyed to a designated Run of Mine (ROM) stockpile area.

The material crushed and screened through a screening and crushing facilities (in-pit crusher, ROM cone crushers, Kawasaki crushers).

Blast-hole material is transported 80 ton rear-tipping trucks or haulers primary crusher (jaw-crusher) for initial size reduction or crushing. This primary crushing step reduces the size of the ore from a maximum rock size of 700mm to 150mm.

Particles with a diameter greater 75mm is removed by scalping screens and allowed it to be crushed by the secondary crushers (gyrating cone crushers – Nordberg crushers).

The 6 to 40mm material is crushed and screened through a tertiary screening and crushing facility (Kawasaki Crushers).

In pit crushing and screening
Oversize ore is crushed using a “in-pit” jaw crusher to reduce the size of the ore for further downstream processes. A primary crusher with a capacity of 650 tph within the pit reduces ore to less than 150 mm. The crushed ore is conveyed over a distance of 1.8 km to the primary stockpile.

Crushing, screening and washing (ore processing)
Ore from the ROM stockpile is conveyed to two parallel circuits comprising scalping screens, cone crushers and double-deck sizing screens and a horizontal dewatering screen at the processing plant.

Lumpy material (– 75 +6 MM) from the processing plant is stockpiled in marked allocated lumpy product stockpile area (Gantry 7) prior to being sent to the load out station using front end loaders. The product is conveyed to railway trucks via the load out section for sale to third parties.

Slimes material from the processing plant is sent to the tailings dam for disposal.

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