Geochemistry is an integrated field of chemistry and geology. It deals with the tools and principles of chemistry in order to explain the mechanisms behind major geological systems such as the Earth’s crust and its oceans. The domain of geochemistry extends beyond the Earth, covering the entire Solar System, and has made crucial contributions to the understanding of a number of processes. A few of such processes are mantle convection, planet formation, and the origins of granite and basalt. Some of the subfields of geochemistry are aqueous geochemistry, biogeochemistry, cosmochemistry, isotope geochemistry, organic geochemistry, photogeochemistry and regional geochemistry. This book outlines the processes and applications of geochemistry in detail. It aims to shed light on some of the unexplored aspects of geochemistry and the recent researches in this field. As this field is emerging at a rapid pace, the contents of this book will help the readers understand the modern concepts and applications of the subject.