Underground Mining in Africa
by Ina King (Potgieter) April 01, 2019
Since the early 1990s, with the enactment of the 1991 Minerals Act, progress has been made regarding mining land rehabilitation and mine reclamation. Communities living in the vicinity of un-rehabilitated mining land face long-term risk and abandoned mines leave a legacy of pollution and the risk to life due to illegal mining operations.
Mining has changed a lot from the images we have of men with shovels toting canaries to make sure the air underground was not toxic. The last canary was used in a coal mine in 1987.
No two mines are alike. Technology, design and mining method rest on considerations like the type of ore being mined, composition of surrounding rock, orientation of the ore deposit as well as simple economics. All underground mines have some crucial components in common: ventilation shafts to clear toxic fumes from drilling and blasting; escape routes; access shafts to lower workers and equipment; ore-transport tunnels; recovery shafts to carry excavated ore to the surface; and communication systems to send information back and forth between the surface and the depths.
What is Underground Mining?
Underground mining is the process of extracting minerals and ores that are buried too far underground to be mined using surface mining methods. Underground mines are the alternative to surface mines. Underground coal mines can drive 750 meters, uranium mines can reach 2 kilometres. Most underground mines bottom out at about 300 meters. Drilling deep underground in pursuit of minerals may sound simple but doing so safely and productively is a whole different story. Underground mines are more expensive.
There are hard-rock underground mines, and there are soft-rock underground mines. Coal, salt, uranium, phosphate and oil shale live in soft rock. Gold, diamonds, copper, silver, nickel, and zinc deposits live in igneous or metamorphic rock, which is relatively hard, as do diamonds, copper, silver, nickel and zinc.
Underground mining is practical when:
- The ore body is too deep to mine profitably by open pit.
- The grades or quality of the orebody are high enough to cover costs.
- Underground mining has a lower ground footprint than open pit mining.
Why is Underground Mining important to South Africa?
Africa is richly endowed with mineral reserves and ranks first or second in quantity of world reserves of bauxite, cobalt, industrial diamond, phosphate rock, platinum-group metals (PGM), vermiculite, and zirconium.
South Africa is the world’s largest producer of chrome (14 000 Mtpa), platinum group metals (193 tpa), manganese (4.7 million Mtpa) and vermiculite (210 000 tpa). South Africa is the world’s second largest producer of ilmenite (1.17 Mtpa), rutile (130 000 tpa) and zirconium (370 000 tpa), and the world’s fourth largest producer of diamonds, with production around 8.15 Mct of diamonds annually.
About 40% of the world’s total gold reserves are found in the Witwatersrand area. Mponeng Gold Mine near Carletonville is the deepest mine in the world exceeding 4 km!About 40% of the world’s total gold reserves are found in the Witwatersrand area. Mponeng Gold Mine near Carletonville is the deepest mine in the world exceeding 4 km!
Mponeng Gold Mine (AngloGold Ashanti)
AngloGold Ashanti’s Mponeng gold mine, located south-west of Johannesburg in South Africa, is currently the deepest mine in the world. The operating depth at Mponeng mine ranged from between 2.4km to more than 3.9km below the surface by the end of 2012. Ongoing expansions have resulted in deeper digging at Mponeng, pushing the record to beyond the four, kilometre mark. The ore reserve at Mponeng stood at 13.7 million ounces (Moz) as of December 2012. It is currently undergoing expansion to extend the mine life beyond 2040.
Kusasalethu Gold Mine (Harmony)
The Kusasalethu gold mine operated by Harmony is located 75km west of Johannesburg, on the West Wits Line near Carletonville, Gauteng, in South Africa. It is currently the fifth deepest mine in the world as it exploits the Ventersdorp Contact Reef (VCR) up to a depth of 3 276 m below the surface. The Kusasalethu operation comprises of twin vertical and twin sub-vertical shaft systems. The mine employs conventional mining methods in a sequential grid layout.
Gold Mining in South Africa
After more than a century of gold mining in South Africa, South Africa is still the custodian of the world's second largest gold resources at 6 000 tons. Over 50% of all gold reserves are found in South Africa, where the Witwatersrand holds the world's largest gold reef deposit.
Ever since gold was discovered on the Witwatersrand in 1886, South Africans have pioneered and developed techniques for profitably and successfully mining gold ore at considerable depths. Many South African deposits, which remain to be exploited, were left unmined because of inappropriate mining techniques, or the prevailing unattractive gold prices at the time.
The South African goldfields still offer excellent opportunities to investors who believe in the continued value of this precious metal.
