A lichen consists of a photosynthetic microorganism such as, for example, a photosynthetic green alga, which is surrounded by the filaments of a fungus. Moreover, chemical weathering is a gradual process where chemicals react with the minerals in the rock to form new minerals, oxidize or simply dissolve them. Lichens can lead to chemical weathering of rocks via the excretion of organic acids (e.g, oxalic acid) capable of dissolving minerals and chelating metallic cations.
