Biomineralization: Complete conversion of organic substances to inorganic derivatives by living organisms, especially micro-organisms.

Biomineralization, also written biomineralisation, is the process by which living organisms produce minerals, often resulting in hardened or stiffened mineralized tissues. It is an extremely widespread phenomenon: all six taxonomic kingdoms contain members that can form minerals, and over 60 different minerals have been identified in organisms. Examples include silicates in algae and diatoms, carbonates in invertebrates, and calcium phosphates and carbonates in vertebrates. These minerals often form structural features such as sea shells and the bone in mammals and birds.

Organisms have been producing mineralized skeletons for the past 550 million years. Calcium carbonates and calcium phosphates are usually crystalline, but silica organisms (such as sponges and diatoms) are always non-crystalline minerals. Other examples include copper, iron, and gold deposits involving bacteria. Biologically formed minerals often have special uses such as magnetic sensors in magnetotactic bacteria (Fe₃O₄), gravity-sensing devices (CaCO₃, CaSO₄, BaSO₄) and iron storage and mobilization (Fe₂O₃•H₂O in the protein ferritin).

In terms of taxonomic distribution, the most common biominerals are the phosphate and carbonate salts of calcium that are used in conjunction with organic polymers such as collagen and chitin to give structural support to bones and shells. The structures of these biocomposite materials are highly controlled from the nanometer to the macroscopic level, resulting in complex architectures that provide multifunctional properties. Because this range of control over mineral growth is desirable for materials engineering applications, there is interest in understanding and elucidating the mechanisms of biologically-controlled biomineralization.

Mineralization can be subdivided into different categories depending on the following: the organisms or processes that create chemical conditions necessary for mineral formation, the origin of the substrate at the site of mineral precipitation, and the degree of control that the substrate has on crystal morphology, composition, and growth. These subcategories include biomineralization, organomineralization, and inorganic mineralization, which can be subdivided further. However, the usage of these terms varies widely in the scientific literature because there are no standardized definitions. The following definitions are based largely on a paper written by Dupraz et al. (2009), which provided a framework for differentiating these terms.

Biomineralization, biologically controlled mineralization, occurs when crystal morphology, growth, composition, and location are completely controlled by the cellular processes of a specific organism. Examples include the shells of invertebrates, such as molluscs and brachiopods. Additionally, the mineralization of collagen provides crucial compressive strength for the bones, cartilage, and teeth of vertebrates.

This type of mineralization includes both biologically induced mineralization and biologically influenced mineralization.

Biological mineralization can also take place as a result of fossilization. See also Calcification.