Chemical weathering is the process by which a material breaks down into its component elements through the action of a chemical agent. This type of weathering requires precise temperature conditions and the presence of a chemically-laden fluid. Substances capable of causing chemical weathering include water and acids.
There are three types of chemical weathering: oxidation, dissolution and hydrolysis. Oxidation is the formation of rust on iron caused by prolonged contact with water. Dissolution involves acidic water and porous minerals, such as limestone and other soft minerals. This type of chemical weathering frequently occurs on gravestones, stone statues and building blocks made from porous rocks. The third type of chemical weathering is called hydrolysis. Like dissolution, hydrolysis involves the interaction of acidic water and minerals.
Several secondary factors also promote chemical weathering. Minerals with small particle sizes are much more susceptible to this type of weathering as compared to those with large particles. The ambient climate and the passage of time also influence the scope and extent of chemical weathering. Natural organisms, such as bacteria, algae and fungi, are important catalysts in this type of weathering. Those that produce acid as a digestive by-product have a particularly large impact on the process.