Dilution in mining refers to the unintentional incorporation of waste rock or low-grade material into the ore stream during the extraction process, which reduces the average grade of the mined ore and negatively impacts the economics of mineral processing. Dilution occurs when blasting, loading, or hauling activities cause adjacent waste material to mix with the target ore, or when ore boundaries are not accurately delineated and adhered to during extraction. In bauxite mining, dilution might involve the inclusion of silica-rich overburden material. In gold mining, dilution from barren host rock reduces head grade and increases the tonnage that must be processed to recover the same amount of gold. In iron ore mining, dilution with low-iron or gangue materials reduces the product's Fe content, while in diamond mining, the introduction of non-kimberlitic waste dilutes the diamond-bearing ore. Dilution is typically expressed as a percentage and is a critical metric in mine planning and operational grade control. Strategies to minimize dilution include precise geological modeling, accurate grade control drilling, careful blast design, and selective mining methods.
