Book excerpt: Volume 39 of Reviews in Mineralogy and Geochemistry about Transformation Processes in Minerals summarises the current state of the art. The selection of transformation processes covered here is by no means comprehensive, but represents a coherent view of some of the most important processes which occur specifically in minerals. Contents: Rigid unit modes in framework structures Strain and elasticity at structural phase transitions in minerals Mesoscopic twin patterns in ferroelastic and co-elastic minerals High-pressure structural phase transitions Order-disorder phase transitions Phase transformations induced by solid solution Magnetic transitions in minerals NMR spectroscopy of phase transitions in minerals Insights into phase transformations from Mössbauer spectroscopy Hard mode spectroscopy of phase transitions Synchrotron studies of phase transformations Radiation-induced amorphization