Weathering is the in situ (in position) breakdown of rocks by natural forces into sediments or chemical constituents. Weathering may be physical or chemical. Physical weathering is the mechanical disintegration of rocks into finer particles. Chemical weathering is the decomposition of rocks according to the weathering series, a list of minerals arranged in order of their relative chemical stability at the earth's surface.

Chemical weathering occurs via a variety of processes such as dissolution, oxidation, hydration, or carbonation. These processes alter minerals at the molecular level either producing, as weathering products, different minerals or non-mineral chemical constituents. Based on their chemical stability, some minerals are more susceptible to the agents and processes of chemical weathering than others. A mineral's stability is determined to a large extent by the conditions under which it formed. Many igneous and metamorphic minerals that equilibrated deep within...