In
geology, Polymorphic transformation describes the
transformation of a
mineral into one of its
polymorphs.
Polymorphic transformation has two main processes:
- Reconstructive transformation
This is the slow transformation of one polymorph into another. In this process, bonds between molecules are broken, and new bonds formed. This is a slow transformation due to the large amount of energy required to break and reform bonds. One example of reconstructive transformation is graphite to diamond.
- Displacive transformation
This is the rapid transformation of one polymorph into another by the expansion, distortion or rotation of coordination polyhedra without the existing bonds being broken. In other words, the angles between bonds are changed rather than the bonds being broken and reformed. An example of displacive transformation is the changing of high (or alpha) quartz to low (or beta) quartz.