CIL & Gravity Gold Recovery at Geita Mine, Tanzania

Source: Unnamed_Company_42 (2026)
Website: https://www.anglogoldashanti.com/portfolio/africa/geita/

Critical Data

Overview

AngloGold Ashanti’s Geita Gold Mine in Tanzania operates a state-of-the-art 5.2 million tonnes per annum (Mtpa) carbon-in-leach (CIL) process plant designed to recover gold from sulphide ore. Commissioned over two decades ago, the facility has been continuously optimized, achieving an average gold recovery of 91.3% over the past five years. Approximately 80% of gold is recovered through the CIL circuit, with the remaining 20% recovered via a dedicated gravity concentration circuit using Knelson concentrators. The plant processes ore from multiple sources including Nyamulilima open pit and Nyankanga, Star and Comet, and Geita Hill underground mines. Ore blends are carefully managed to maximize recovery, with individual deposit recoveries ranging from 73% (high-sulphide Star and Comet) to 93.4% (Nyankanga). The flowsheet integrates three-stage crushing, SAG and ball mill grinding, thickening, CIL leaching with ten tanks, and elution/electrowinning for gold concentrate production. Bullion bars with 85-92% purity are shipped to Rand Refinery. The plant runs 24/7 with 96% mill availability and 94% utilisation, delivering a consistent 680 tonnes per hour throughput. Water consumption is 1.6 m³ per tonne, sourced from Lake Victoria and local dams, while power is supplied by the national grid supplemented by diesel generators, with unit energy consumption of 57 kWh/t.

Key Process Stages

• Stage 1: Three-Stage Crushing – Run-of-mine ore is fed to a 1.1m x 1.8m primary gyratory crusher (120mm closed side setting). Secondary and tertiary Sandvik CH660 cone crushers operate in closed circuit with a 40mm double-deck screen to produce -40mm product for the fine ore stockpile (9kt live capacity, 100kt total).
• Stage 2: Grinding Circuit – A two-stage milling process comprising a 9.14m diameter x 5.50m EGL SAG mill (9MW) in open circuit and a 6.71m diameter x 9.6m EGL ball mill (9MW) in closed circuit with Krebs gMax150 hydrocyclones. Target grind size is 80% passing 106µm. Quicklime is added to the mill feed conveyor.
• Stage 3: Gravity Gold Recovery – Cyclone underflow from the gravity cluster feeds a scalping screen (+3mm returned to SAG mill). Undersize reports to two 48-inch Knelson concentrators (G5 cone). Concentrate is treated in an Acacia intensive leach reactor, producing a high-grade gold solution sent to dedicated electrowinning cells.
• Stage 4: Carbon-in-Leach (CIL) Cyanidation – Thickened slurry at 52% solids is pumped through two pre-oxidation tanks followed by ten CIL tanks (each 2,240m³). Sodium cyanide is dosed in two stages (tanks 3 and 6). Oxygen is sparged, with hydrogen peroxide supplementation. pH is maintained at 10.5. Loaded carbon is advanced counter-current and recovered from tank 3.
• Stage 5: Elution, Electrowinning and Smelting – Loaded carbon undergoes acid wash (3% HCl) and then elution via the AARL method using caustic soda at high temperature/pressure. Pregnant solution is electrowon in eight stainless steel cells (12 cathodes each) over 8-12 hours. Gold concentrate is filtered, dried, smelted, and poured into bullion bars (85-92% Au).

Additional Interesting Data and Summary

The Geita CIL plant’s technical performance is underpinned by robust design and operational optimization. The grinding circuit’s two 9MW mills achieve the target P80 of 106µm, while the gravity circuit recovers free gold early, reducing load on downstream cyanidation. Oxygen supply is maintained by two 10 t/day pressure swing adsorption plants, and intertank Kemix screens (820µm) retain carbon effectively. The elution column and acid wash column each have 14-tonne capacity, and the rotary kiln regenerates carbon for reuse. Environmental performance is a key focus: water recycling is practiced, and tailings are stored in an engineered tailings storage facility (TSF) that underwent a buttress reinforcement in 2024, with another lift planned for 2027. AngloGold Ashanti has connected to the Tanzanian national grid (Tanesco) in mid-2024, reducing the emission factor from 0.67 tCO₂e/kWh (diesel) to 0.30 tCO₂e/kWh (grid hybrid), achieving a 72 kt CO₂e annual reduction by 2030. Power costs dropped from $0.20/kWh (diesel) to $0.081/kWh (grid). Water sourcing from Lake Victoria and mined-out pits is supplemented by boreholes, with advanced treatment and recycling facilities. The mine’s infrastructure includes on-site housing, a medical clinic, airstrip, and robust communication networks. Community investments in schools, water systems, and health centres support local development. The gold doré produced meets LBMA Good Delivery standards and is sold on the open market. Future outlook includes continued blend optimization across ore sources to maximize recovery, especially for high-sulphide Star and Comet ore (73-86% recovery). The plant’s long operational history (over 20 years) and continuous improvement programs ensure stable, cost-effective gold production. Total LOM operating costs are estimated at $4,336 million with all-in costs of $1,379/oz Au. The processing cost per tonne is approximately $19.15, contributing to the mine’s economic viability. Sustainability initiatives like grid power transition and water stewardship align with AngloGold Ashanti’s decarbonisation goals. Overall, the Geita gold recovery plant exemplifies a mature, high-efficiency operation with a clear path to reduced environmental footprint and sustained production.

Key Processes: Flotation, CIP/CIL, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Silver, Zinc, Lead