Hans-Rudolf Wenk is Professor of the Graduate School in the Department of Earth and Planetary Science at the University of California, Berkeley. Since joining the Berkeley faculty, he has been engaged in teaching and research, covering a wide field of mineralogy, from feldspars to carbonates, metamorphic rocks to shales, and from the Earth's surface to the inner core. His particular focus has been on microstructures, investigated using electron microscopy and synchrotron X-rays. Andrey Bulakh is Professor in the Department of Mineralogy at St Petersburg State University. He is a specialist in mineralogy, geochemistry and the origin of alkaline rocks and carbonatites. More recently, he has studied the history of ornamental stones in architecture. He has written several books that are widely used at Russian universities, and was a long-time member of the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association.