I was invited to write this book as part of the Minerals, Rocks and Organic Materials Series of Springer-Verlag by Professor Peter J. Wyllie in 1974. Ophiolites have preoccupied me ever since 1948 as a graduate student and up to the present time as part of my research with the U.S. Geological Survey. During this period ophiolite, an obscure European geological term, has attained an ever-increasing importance, is now used to include all fragments of ancient oceanic lithosphere incorporated into the orogenic zones of modern and ancient continental margins, and is a standard part of the plate...