Geita Gold Mine Processing Circuit: Gravity Recovery and CIL

Geita is a mature open-pit and underground gold operation in northwestern Tanzania. Its central processing plant combines three-stage crushing, SAG and ball milling, Knelson gravity recovery and carbon-in-leach (CIL) cyanidation. This profile consolidates MillMatters’ previous Geita circuit summaries and reconciles the capacity and recovery figures reported in the 2023 and 2025 technical records.

Geita processing flowsheet

The plant treats ore delivered from the Nyamulilima open pit and the Star and Comet, Nyankanga and Geita Hill underground mines. Hardness, grade, weathering and sulphide content vary by source, so feed blending is an important part of both throughput and recovery control.

1. Three-stage crushing

Run-of-mine ore is fed to an approximately 1.1 m × 1.8 m primary gyratory crusher. Secondary and tertiary cone crushers operate with double-deck screening to produce material below approximately 40 mm for the fine-ore stockpile. The stockpile provides surge capacity between mining and the continuous grinding circuit.

2. SAG and ball milling

Fine ore is processed in a 9.14 m diameter × 5.50 m effective-grinding-length SAG mill rated at 9 MW. A 6.71 m diameter × 9.6 m effective-grinding-length ball mill, also rated at 9 MW, operates in closed circuit with hydrocyclones. Technical records cite a nominal plant rate near 680 t/h and a target grind around a P80 of 106 µm. Quicklime is added around the mill-feed system to establish alkaline conditions for downstream cyanidation.

3. Knelson gravity recovery

A dedicated cyclone-underflow stream is screened before two 48-inch Knelson concentrators recover liberated coarse gold. Oversize screen material returns to grinding. Knelson concentrate is treated in an Acacia intensive-leach reactor, and the resulting high-grade solution is sent to dedicated electrowinning. Recovering coarse gold early reduces the recoverable gold inventory carried into the much larger CIL circuit.

4. Thickening, pre-oxidation and CIL

Ground slurry is thickened to approximately 52% solids before two pre-oxidation tanks and ten CIL tanks of approximately 2,240 m³ each. Current company reporting describes this combined section as 12 leach tanks. Oxygen is sparged into the circuit, with supplementary hydrogen peroxide available, while pH is controlled near 10.5. Cyanide is staged within the adsorption train, and activated carbon advances counter-current to slurry.

5. Elution, electrowinning and smelting

Loaded carbon is acid-washed and stripped using the AARL process. Pregnant eluate is treated in electrowinning cells; the gold-bearing concentrate is filtered, dried and smelted into bullion. Carbon is thermally regenerated and returned to the CIL circuit.

Principal equipment and reported operating data

Equipment values are drawn from technical-report descriptions. Actual rate, grind and recovery vary with the ore blend and plant availability.

Ore blending and recovery

Geita is not a single, uniform orebody feeding a fixed metallurgical response. The operation blends material from open-pit, underground and stockpile sources with different hardness, sulphide content and gold deportment. Recent technical material cites an average plant recovery near 91.3% over a five-year period, but individual ore domains and blends can be materially lower or higher.

This variability explains why current improvement work emphasizes gravity recovery, product size and dissolved oxygen. Coarse liberated gold benefits from the Knelson-Acacia route, while adequate grinding and oxygen transfer support cyanide kinetics in the CIL train. A single recovery percentage should therefore be treated as a period average, not a guaranteed result for every source.

What changed between the technical records?

The older 5.2 Mt/a and current 5.4 Mt/a figures describe successive reporting bases for the same plant. The 5.5 Mt/a value used in one former MillMatters summary is not retained because it conflicts with AngloGold Ashanti’s current filing.

Power, water and tailings

Since September 2024, the Tanzanian national grid has been Geita’s principal electricity source. The mine retains approximately 40 MW of diesel generation for backup. This was a major infrastructure change, but it did not alter the metallurgical flowsheet.

The operation is permitted to pump approximately 25,000 m³/d of raw water from Lake Victoria and also recycles process water. AngloGold Ashanti’s 2025 filing says the existing tailings-storage facility is being prepared for operational closure while a new facility proceeds through design and permitting. These changes should be tracked separately from the proposed processing-plant expansion.

Potential plant expansion

AngloGold Ashanti began a detailed feasibility study in the fourth quarter of 2025 after a conceptual study indicated that a plant expansion, coordinated with higher open-pit and underground mining rates, could support gold production around 600,000 oz/y for at least ten years. The study is expected to finish in 2027.

No expanded plant capacity or final equipment list should be treated as approved operating data yet. Until a feasibility design and investment decision are published, Geita’s current reference circuit remains the 5.4 Mt/a crushing, grinding, gravity and CIL plant described above.

Technical-report library and sources

Additional resources and industry links

• AngloGold Ashanti: Geita operation profile
• AngloGold Ashanti 2025 operational profiles and report suite
• AngloGold Ashanti 2025 Annual Report (PDF)
• MillMatters: Gold cyanide leaching and CIL process guide
• MillMatters: Gravity concentration equipment and circuit guide
• MillMatters: Mine tailings management guide