is the process by which living organisms produce minerals, often to harden or
stiffen existing tissues. It is an extremely widespread phenomenon; all five
taxonomic kingdoms contain members that are able to form minerals, and over
60 different minerals have been identified in organisms. Examples include
silicates in algae, carbonates in diatoms
and 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 mineralised skeletons for
the past 550 million years. 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