Gangue

Gangue is the commercially worthless material that surrounds or is mixed with ore. In mining and mineral processing, it denotes the non-valuable minerals and rock that accompany ore minerals and must be separated during beneficiation. In coal mining, gangue also refers to the non-combustible mineral matter within coal, including quartz, clays, feldspars, calcite, and pyrite.

The composition of gangue varies by deposit and ore type. Common gangue minerals include quartz, feldspar, calcite, clays, mica, and various rock fragments. The presence of gangue lowers the ore grade and increases energy, chemical, and physical requirements for processing, handling, and waste disposal.

Separation techniques are designed to remove gangue from ore, improving recoveries and product quality. Methods include crushing and grinding, flotation, gravity separation, magnetic separation, and leaching. In coal preparation plants, washing removes gangue to reduce ash content and improve calorific value.

Economically, the gangue-to-ore ratio influences mine planning, metallurgical design, and environmental management. Large quantities of gangue lead to tailings production and potential storage and contamination concerns.