Biomineralisation's the process by which living organisms produce minerals, often to harden or stiffen existing tissues. It's an extremely widespread phenomenon; all five taxonomic kingdoms contain members that're 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… (More on Biomineralization)