Mponeng is the deepest level shaft in the world, with a depth of 3 891 metres below datum and 2 062 metres below sea level. The mine, which began producing in 1986, is near the town of Carletonville, some 90km south-west of Johannesburg. The mine exploits the Ventersdorp Contact Reef, its primary orebody, employing mostly breast-mining methods. The economic reef horizons are mined at depths of between 3 160m and 3 740m below surface. Ore mined is processed at the Mponeng gold plant using conventional gold leaching methods carbon-in-pulp gold recovery technology(“Mponeng Mine | South Africa | Underground | Harmony,” n.d.).
Rock walls mine reach temperatures 60°C and humidity levels can exceed 95%. To keep things cool, more than 6,000 tonnes of ice slurry are pumped into underground reservoirs, and giant fans aid air flow. Every day, about 5,000 lb of explosives are used and 6,400 tonnes of rock are excavated(Deepest Mine, n.d.).
The Mponeng gold project is situated in the West Wits mining district, about 65km west of Johannesburg, South Africa. It lies near the town of Carletonville, on the border between Gauteng and North West provinces. The gold deposit sits on the north-western rim of the Witwatersrand Basin. The main reef horizon mined at the Mponeng mine is the Ventersdorp Contact Reef (VCR), which caps the Witwatersrand Supergroup. The mine can also access the Carbon Leader Reef (CLR) located approximately 800m below the VCR.
The Mponeng ore body underwent a series of deep burials, fracturing, and alterations. The gold and other elements are believed to have precipitated through the reaction of hydrothermal fluids at high temperatures along the reef horizon. The proven and probable ore reserves of the Mponeng mine were estimated to be 7.7 million tonnes (Mt) grading 8.53g/t gold as of June 2021. The contained gold reserves were estimated to be 2.1 million ounces (Moz). The measured, indicated, and inferred ore resources are estimated to be 52.7Mt containing 23.5Moz of gold(“Mponeng Gold Mine,” n.d.).
Imagine working miles beneath the Earth’s surface, where rock temperatures soar and the pressure is immense! The world’s deepest underground mine is a testament to engineering and human endurance. What aspects of extreme depth mining fascinate you most?
Reference:
-
Deepest mine. (n.d.). Guinness World Records. Retrieved June 10, 2025, from https://www.guinnessworldrecords.com/world-records/66169-deepest-mine.html
-
Mponeng Gold Mine. (n.d.). NS Energy. Retrieved June 10, 2025, from https://www.nsenergybusiness.com/projects/mponeng-gold-mine/
-
Mponeng Mine | South Africa | Underground | Harmony. (n.d.). Harmony Gold Mining Company Limited. Retrieved June 10, 2025, from https://www.harmony.co.za/operations/south-africa/underground/mponeng/
-
tufbag. (2022, June 30). Which Underground Mining Support Products Are The Best? Tufbag. https://www.tufbag.com/which-underground-mining-support-products-are-the-best/
