Chrome Ore
DCM is situated in the Eastern Limb of the Bushveld Complex, a mineral-rich area made from persistent layers of mafic and ultramafic rocks, containing the world’s largest known resources of the platinum group metals (PGMs), chromium and vanadium. The sixth chromite seam in the Lower Group (LG6) is an important source of chromite ore and is the ore body extracted at the mine. In the Eastern Lobe, in the vicinity of the mine, the strike is nearly north-south, with a dip of approximately 10 degrees towards the west. The average thickness of the LG6 seam is about 1.86 metres in the mine area.
DCM production
DCM mines Chromite Ore using low-profile mechanised equipment, including personal carriers, cable tech bolters and face scrapers, and the board and pillar method. Low-profile drill rigs are used to drill chrome seams into the panels. These faces are then charged and blasted at the end of the shift.
Load, haul, dump (LHD) loaders collect the ore from the faces following blasting and transport it to well space tipping points, where it is tipped on vibratory feeders. From here it is transported on a herringbone conveyor network system to the surface plant.
The run of mine (ROM) feed from underground is stored on a live stockpile before processing in a beneficiation plant. The crushed chrome ore is conveyed to a classification section where coarse and fines fractions are separated before being subjected to further processing i.e. Dense medium circuits, and mill & spiral section.
Coarse material is fed to Dense medium section to produce lumpy products and Discard waste. The fine fraction is processed through mill & spiral to produce different grades of metallurgical products i.e. Metallurgical grades (low & high), Chemical , Foundry sand and their fine wastes. All chrome products are transported to local and international customers via road and rail systems.
All chrome products are sent to the smelters and third-party customers as per their requirements by truck.
Mining environment
The Steelpoort Chromitite Seam (SCS) is the only seam that is currently being exploited at DCM. It outcrops on the DCM surface area and extends to a depth of more than 500m below surface. The seam is characterised by a Chromitite package varying in thickness between 1.60 – 1.86m. It is bounded at the top and bottom by Pyroxenite with disseminated Chromitite-Pyroxenite characterising the immediate hanging wall and footwall contacts. The orebody strikes in a north-south orientation with a gentle 10o dip towards the west. Measuring up to approximately 30cm above the SCS, there is a disseminated Chromitite-Pyroxenite stringer, referred to as the Steelpoort Chromitite Leader (SCL). The entire unit from the SCS contact to the SCL is referred to as the False Hanging Wall.
Reserve estimate
The current LoM is 35 years, and this includes those reserves scheduled post the date for which the mining right was awarded. Steady state production for the operations is planned at approximately 215kt of run of mine (RoM) per month (2.64Mt RoM per annum) for the DCM operations. The steady state target can be maintained by upgrading inferred resources to reserves. All development is done on reef and therefore all the RoM is trammed to the plant.
As at 30 June 2023, the total reserves at DCM were estimated at 65.70Mt, with proven and probable reserves being 41.97 Mt and 23.73 Mt, respectively.
Mineral extraction process
DCM utilises a mechanised bord and pillar mining method to extract ore from the underground workings. All development (declines) and stoping is done on-reef. The declines are developed on an apparent dip of 8° from which each stope section or strike is developed on a very shallow apparent dip that is sub-parallel to the strike direction of the ore body. The sequence of mining allows for the top sections or strikes to lead in an underhand face configuration.
Each strike consists of seven or nine bords that are connected to each other via ventilation holings. The bords are mined at a maximum span of 10m and the ventilation holings are 8m or 10m wide. An average stoping height of 2.2m is maintained in most production sections, apart from the undercutting of the False Hanging Wall project section. In this section a designed stope height of 2.0m is maintained.
Beneficiation
The Dwarsrivier Chrome Mine’s beneficiation plant has a plant feed production capacity of 200 000 tons per month.
Unit processes are divided into the following circuits:
- Crushing and screening
- DMS (Dense Media Separation) with drum and cyclone
- Milling and spiral plant
- Tailings recovery plant
Final products realised are:
- Lumpy
- Chemical grade
- High grade metallurgical grade
- Low grade metallurgical grade
- Foundry grade
- Tailings
Application
Chromite ore is primarily used as the main raw material for the production of chromium metal and its compounds. The vast majority of chromite ore is used in the production of ferrochrome, which is an essential ingredient in stainless steel. Ferrochrome provides the corrosive resistance properties to stainless steel. Other applications include pure chromium metal, which has various applications in superalloys, aerospace materials, and other specialised uses, and various chemicals like chromium sulfate and chromium salts, which have a range of industrial applications.
The most common uses of chrome include:
- Manufacturing of stainless steel.
- Casting and chromium plating for surface protection.
- Chemical industries use chromium compounds for the tanning of leather, dyes and paints.
- Foundry sands are used for casting of moulds.
- Applications also extends to creating refractory bricks for furnaces and so on.
