Kloof Gold Mine, located in the West Rand Goldfield of South Africa, was one of the country’s major gold producers before its closure. The ore dressing (processing) methods used at Kloof and similar South African gold mines typically involved several stages to extract gold from the ore efficiently. Here’s an overview:
1. Ore Characteristics
– Gold-bearing ore: Typically contained gold in quartz-pebble conglomerates (e.g., the Witwatersrand reefs).
– Low grade: Often required processing large volumes of ore to extract small amounts of gold.
– Sulfide content: Some ores had pyrite or other sulfides associated with gold.
2. Ore Dressing Process at Kloof
The processing flow generally included:
# (a) Crushing & Milling
– Primary crushing: Ore was crushed using jaw or gyratory crushers.
– Secondary crushing & milling: Further reduced to fine particles using ball mills or SAG (Semi-Autogenous Grinding) mills.
– Goal: Liberate gold particles from the host rock.
# (b) Gravity Separation (Optional)
– Some free-milling gold was recovered using jigs, shaking tables, or centrifugal concentrators.
– Used for coarse gold before cyanidation.
# (c) Flotation (if sulfide-rich)
– Froth flotation separated sulfide minerals (e.g., pyrite) containing fine gold.
– Concentrates were further processed via roasting/bio-oxidation before leaching.
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# (d) Cyanidation & Carbon-in-Pulp (CIP) / Carbon-in-Leach (CIL)
– Leaching: Crushed ore was mixed with a cyanide solution to dissolve gold.
– Adsorption: Activated carbon captured dissolved gold from the slurry.
– Elution & Electrowinning: Gold-loaded carbon was stripped, and gold was recovered via electrowinning/smelting.
# (e) Tailings Management
– Waste material (tailings) was stored in dams, sometimes reprocessed for residual gold.
3. Challenges at Kloof & Similar Mines
– Deep-level mining: High costs due to depth (~3 km), seismic risks, and cooling needs.
– Declining grades: Lower ore quality increased processing costs.
– Environmental concerns: Cyanide use and tailings management required strict controls.
4. Current Status
Kloof Mine, previously operated by Sibanye-Stillwater, has faced closures due to economic