The discovery of comatose – ultramafic volcanic rocks – was one of the most important petrological advances on this century. Not only are comatose economically important as host rocks to many nickel deposits, but they are also of great scientific interests since they provide unique information on the early history of the Earth's crust and upper mantle. This book should come to be regarded as the definitive volume on comatose. Over forty acknowledged authorities on the subject have been brought together by the editors to provide a comprehensive survey of what is known about comatose a decade after their discovery. These contributors – including M. J. & R. P. Viljoen, the discoverers of the rocks – also present much new and important work. Part of the book is devoted to concise and up-to-date- descriptions of the better known occurrences of komatiites throughout the world and in areas ranging in age from Archaean to Tertiary. Other sections include chapters on all aspects of the rocks: definition, analogous modern rocks, textures, metamorphism and alteration, geochemistry, economic geology and petrogenesis. This book should be of enduring value to all igneous petrologists, to geologists specializing in Precambrian rocks, and to economic geologists concerned with the mineral resources of Archaean and Lower Proterozoic terrains. N. T. Arndt is a Research Fellow at the Max Planck Institute, Mainz, West Germany, and was previously Assistant Professor at the University of Saskatchewan, Canada. E. G. Nisbet is Associate Professor at the University of Saskatchewan, Canada, and Honorary Fellow of the Department of Geology, University of Zimbabwe. He was previously at Cambridge, ETH-Zurich, and Oxford.