- © The Mineralogical Society Of America
In the most general sense, biomineralization is a process by which organisms produce materials solutions for their own functional requirements. Because so many biomineral products are derived from an initial solution phase and are either completely crystalline or include crystalline components, an understanding of the physical principles of crystallization from solutions is an important tool for students of biomineralization. However, crystal growth is a science of great breadth and depth, about which many extensive texts have been written. In addition, there are already other thorough reviews that specifically address the crystal growth field of study as it relates to biomineral formation. Consequently, the goals of this chapter are both modest and specific. It is intended to provide: 1) a simple narrative explaining the physical principles behind crystallization for those who are completely new to the topic, 2) a few basic equations governing nucleation and growth for those who wish to apply those principles—at least in a semi-quantitative fashion—to experimental observations of mineralization, and 3) an overview of some recent molecular-scale studies that have revealed new insights into the control of crystal growth by small molecules, both organic and inorganic.
This last topic gets to the heart of what makes crystallization in biological systems unique. Every day, many tons of crystals are produced synthetically in non-biological processes, but by-and-large, the degree of control over nucleation and growth achieved by deterministic additions of growth modifiers or the presence of a controlling matrix is very minor. More commonly, crystal growers view modifying agents as unwanted impurities and work extremely hard to eliminate them from the starting materials. Indeed, the degree to which living organisms are able to control the crystallization process is most striking when contrasted to the products of such synthetic crystallization processes. This contrast applies to both the compositional differences that …