The Chemistry of Biologically Produced Minerals

More than 60 different minerals are produced by a huge variety of organisms. Many of these minerals differ substantially from their inorganic counterparts not only in shape and orientation, but in their chemistry. Trace element concentrations, as well as stable isotopic compositions are often controlled by the biology. Many biogenic minerals contain occluded macromolecules that can change their mechanical properties. Even more surprising is that single crystals produced by organisms often have a bulk and surface texture consisting of nano-spheres, quite unlike crystals grown from saturated solutions. This texture is a hallmark of a crystal formation pathway via highly disordered and unstable precursor phases. The precursor phases are composed of nano-spheres that are formed in vesicles inside cells. In fact a surprisingly large variety of cells have such mineral-bearing vesicles, even though they are not known to be directly involved in the formation of mineralized tissues. The involvement of disordered precursor phases in biological crystal formation has inspired many non-biological studies of this phenomenon. These studies have in turn revealed that growth of crystals from precursor phases is widespread and that a common mechanism of growth is by amorphous particle attachment as opposed to ion-by-ion accretion. By understanding these alternate processes and mechanisms of crystal growth both in the inorganic world and in biology, we can better understand the perplexing properties of many biogenic minerals.

1. Gal, S. Weiner and L. Addadi: “A perspective on underlying crystal growth mechanisms in biomineralization: solution mediated growth versus nanosphere particle accretion”, CrystEngComm 2015