The Abraham Gottlob Werner Silver Medal was awarded to Professor Dr. François Holtz (Institute of Mineralogy, Leibniz University Hannover). François Holtz is one of Europe's leading petrologists of igneous rocks and is among the world's most renowned experimental petrologists. At the beginning of his scientific career, he worked on the petrogenesis, field relationships, and geochronology of Hercynian granites. Since 1990, he has pursued, with great enthusiasm and outstanding experimental expertise, the systematic quantification of the role of volatile components in controlling the physical properties and phase petrology of silicate melts. The results of these highly systematic studies have had, and continue to have, a fundamental impact on our current understanding of the evolution of magmas within the Earth's crust, as well as on their key properties, including viscosity and the solubility of elements such as sulfur, chlorine, and fluorine. Through this work, François Holtz has opened new possibilities for the interpretation of petrological, geochemical, and geophysical observations at volcanoes.