Leaching is a natural or induced process that involves the removal or extraction of soluble constituents from a rock, soil, or ore. The dissolved materials extracted through this process are collectively referred to as the leachate. Leaching typically occurs as a result of the action of percolating waters, such as rainfall, groundwater, or other natural water sources. These waters infiltrate the material and dissolve or disperse its soluble components, often carrying them away to nearby water bodies or soil layers.

This process is commonly observed in the weathering of rocks and minerals, leading to the formation of new compounds and soil types. In agriculture, leaching can cause the loss of vital nutrients from the soil, negatively impacting crop growth and soil fertility. In the mining industry, leaching is often employed as a technique to extract valuable metals from low-grade ores through the use of chemicals, such as cyanide or sulfuric acid. Environmental concerns associated with leaching include groundwater contamination and soil degradation due to the migration of harmful substances, such as heavy metals or chemicals, into surrounding ecosystems.