how gold processed in canada
Gold processing in Canada follows a well-established series of steps, from extraction to refining, ensuring high purity and quality. The methods vary depending on the type of deposit, whether it’s hard rock (lode) or placer (alluvial) gold. Here’s an overview of the typical gold processing methods used in Canadian mines.
1. Exploration and Mining
Before processing begins, extensive exploration is conducted to identify viable gold deposits. Once a site is confirmed, mining operations commence. In Canada, both open-pit and underground mining are common. Open-pit mining is used for near-surface deposits, while underground mining targets deeper veins. Placer mining, though less common today, involves extracting gold from riverbeds and sediments using techniques like panning or sluicing.
2. Crushing and Grinding
After extraction, the ore is transported to a processing plant where it undergoes crushing and grinding. Large chunks of ore are reduced to smaller pieces using jaw crushers or cone crushers. The material is then ground into a fine powder in ball mills or SAG (semi-autogenous grinding) mills. This step increases the surface area of the ore, making it easier to extract gold during subsequent stages.
3. Concentration and Separation
The ground ore is mixed with water to form a slurry, which is then processed using gravity separation or flotation methods. Gravity separation relies on the density difference between gold and other minerals, often using centrifuges or shaking tables. Flotation involves adding chemicals that make gold particles hydrophobic (water-repellent), allowing them to attach to air bubbles and rise to the surface for collection.
4. Leaching and Recovery
For finer gold particles, cyanidation is commonly used—a process where gold dissolves in a diluted cyanide solution. The resulting liquid (pregnant solution) is then treated with activated carbon or zinc dust to precipitate the gold (carbon-in-pulp or Merrill-Crowe processes). Alternatively, some mines use heap leaching, where crushed ore is piled on impermeable pads and irrigated with cyanide solution over weeks or months to dissolve the gold slowly.
5. Refining and Smelting
The recovered gold undergoes further purification to remove impurities like silver or copper. Smelting involves heating the material in a furnace at high temperatures to separate precious metals from slag (waste material). The molten gold is poured into molds to form doré bars—a semi-pure alloy typically containing 80-95% gold—which