How does mineral processing separate valuable minerals from gangue?

Mineral processing separates valuable minerals from waste rock, known as gangue, through a multi-stage approach that begins with physical liberation and follows with concentration techniques.

Comminution

Before separation can occur, the ore must be physically broken down to liberate the valuable minerals from the interlocked waste rock. This process, called comminution, involves crushing the ore into smaller sizes and grinding it into a fine powder. The required fineness of the powder depends on how the desired mineral is disseminated within the ore.1

Concentration Methods

Once liberated, the minerals are separated from the gangue using methods that exploit differences in physical or chemical properties:

• Flotation: This is the most widely used method for fine-grained minerals. It utilizes the surface properties of minerals, specifically their wettability. By adding chemical reagents, valuable minerals are made hydrophobic (water-repelling) so they adhere to air bubbles and rise to the surface as a froth, while hydrophilic (water-attracting) gangue remains in the pulp.23
• Gravity separation: These methods rely on density differences. Techniques include heavy-media separation, jigging, and the use of spirals or shaking tables to stratify particles based on their weight, allowing heavier valuable minerals to be collected separately from lighter gangue.4