This book examines agate provinces through the lens of plate tectonics, stratigraphy, agatization, and more. It delves into the physical and chemical properties of agate deposits, their environments of formation, and related silica deposits like opal, chert, and petrified wood. Examples, illustrations, maps, and thin-section photos illuminate structural, chemical, and temporal controls. Plate tectonics and lithotectonics are explored to provide a deeper understanding of the volcanic processes behind agate formation.