Polymorphism

Silica Polymorphs. Image Source: Unknown

Situation in which a single chemical composition can exist with two or more different crystal structures. Transformations between crystal structures of the same chemical compound are called polymorphic transformations. These are of three types of polymorphism: displacive, reconstructive, and order-disorder. Examples of polymorphs include:

  1. Silica (SiO2): α quartz, β quartz, coesite, stishovite, tridymite, and cristobalite (see chart)
  2. Aluminosilicates (Al2SiO5): kyanite, andalucite, and sillimanite
  3. Carbon (C): graphite, diamond, and lonsdalite (among others).

Some or all content above used with permission from J. H. Wittke.