The idea for a series of volumes dealing with the 'Landmark Papers' defining the development of different areas of our science was discussed at a meeting of the council of the Mineralogical Society of Great Britain & Ireland in 2002. Council approved the idea by reasoning "which of us would not be interested in a collection of papers illustrating the development of a branch of mineralogy?" This, the third collection of such papers has been selected by Bernard Evans of the University of Washington. Much of Earth's crust and arguably parts of its mantle are composed of rock that has undergone...