Crystal growth recrystallization

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

The habit of pharmaceutical compounds has been used for purposes of identification, although the method can only be reliably used when the crystallization solvent used to generate the test crystals is carefully controlled. Since the faces of a crystal must reflect the internal structure of the solid, the angles between any two faces of a crystal will remain the same even if the crystal growth is accelerated or retarded in one direction or another. Toxicologists have made extensive use of microscopy following multiple recrystallization, and they have developed useful methods for compound identification [5]. 

G. Ibe, K. Lucke, Growth selection during recrystallization of single crystals, in Recrystallization, Grain Growth and Textures, 1966, p. 434. 

Although most additives that have been studied retard growth on all faces of the crystal, there are some which definitely promote growth on certain faces. For example, repeated recrystallization of lactose removes growth-promoting trace substances, so that crystal growth is much slower in supersaturated solutions of this lactose than in less purified solutions. The tendency toward spontaneous nucleation is also lowered upon repeated recrystallization. 

On heating there occurs the possibility of renewed crystal growth whereby undeformed crystals are again produced at the expense of the deformed lattice with higher energy content (recrystallization). The broadening of the X-ray lines disappears completely thereby. 

Gel dissolution Zeolite nucleation Crystal growth of the zeolite nuclei Dissolution/recrystallization of metastable phases (Oswald s Law of successive transformations)... 

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