26/01/2026
We bring this episode to a close by discussing the Processing of Gold Ore
Gold ore processing involves a series of steps used to extract gold from its host rock economically and safely. The method chosen depends on the type of ore, gold grain size, and grade.
1. Ore Preparation
a. Mining:
Gold ore is extracted by open-pit or underground mining
Ore is transported to the processing plant
b. Crushing:
Large rocks are reduced in size using jaw crushers and cone crushers
Purpose: liberate gold particles from the rock
c. Grinding:
Crushed ore is ground into fine particles using ball mills or rod mills
Increases surface area for gold recovery
2. Gold Concentration (Pre-Concentration)
a. Gravity Separation:
Used when gold is coarse and free-milling:
* Panning
* Sluice boxes
* Shaking tables
* Centrifugal concentrators (Knelson, Falcon)
👉 Common in artisanal and small-scale mining
3. Chemical Extraction:
a. Cyanidation (Most Common Method)
Used for fine-grained gold:
Gold dissolves in a cyanide solution
Forms a gold–cyanide complex
Methods:
> Heap leaching
> Tank leaching
> Carbon-in-Pulp (CIP)
> Carbon-in-Leach (CIL)
b. Carbon Adsorption:
√ Dissolved gold is absorbed onto activated carbon
√ Gold is later stripped from carbon using heat and chemicals
4. Gold Recovery
a. Electrowinning:
Electric current causes gold to deposit on steel wool cathodes
b. Smelting:
Gold concentrate is melted with fluxes
Produces doré bars (gold + silver)
5. Refining:
Doré bars are refined to produce 99.5–99.99% pure gold
Methods:
✓ Miller process
✓ Wohlwill electro-refining
6. Waste Management:
# Tailings stored in tailings dams
# Cyanide detoxification before discharge
# Environmental monitoring is critical
Types of Gold Ore and Processing Methods
Ore Type Processing Method
< Free-milling gold Gravity + cyanidation
< Refractory gold Roasting, pressure oxidation
< Oxide ore Heap leaching
< Sulphide ore Flotation + cyanidation
Key Challenges:
√ Refractory ores (gold locked in sulphides)
√ Environmental risks (cyanide handling)
√ Recovery efficiency
