Biomineralisation

Biomineralisation is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. 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. As a result biomineralization is employed in metal extraction.

The aim of biomimetics is to mimic the natural way of producing minerals such as apatites. Many man-made crystals require elevated temperatures and strong chemical solutions whereas the organisms have long been able to lay down elaborate mineral structures at ambient temperatures. Often the mineral phases are not pure but are made as composites which entail an organic part, often protein, which takes part in and controls the biomineralisation. These composites are often not only as hard as the pure mineral but also tougher, as at last, the micro-environment controls biomineralisation.

Biominerals generally consist of either calcium, iron, or silicon. The hardness of biominerals depends on both the degree of mineralisation (i.e., structure) and the type of mineral.