orthochemical rock

Orthochemical rocks are a type of sedimentary rock where the carbonate minerals, such as calcite and dolomite, form in situ rather than being transported as clastic material. This contrasts with allochems, which are discrete grains like fossil fragments or ooids that have a history of transport and deposition.1

Orthochemical material includes microcrystalline carbonate mud (micrite) and sparry carbonate cement (sparite). Micrite often originates from the activity of algae, which produce tiny needles of aragonite that form mud after their death. Sparite, on the other hand, can be recrystallized micrite or directly precipitated calcium carbonate. These processes are considered geochemical, occurring within the depositional environment. Chemical precipitation is the formation of a solid substance from a solution, often used to remove ions or isolate pure compounds.123