Geochemistry is referred to as the study of the phenomena that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. It is vital to understand the processes related to production of economic concentrations of minerals by hydrothermal, magmatic, metamorphic, hydraulic, or weathering agents. Geochemistry encompasses the topics such as the Earth's aggregate physical and chemical state, thermodynamics, solutions and simple phase relations and mineral chemistry. The chemistry of natural waters, the chemistry of igneous rocks, chemical controls on soil formation, diagenesis, metamorphism, hydrothermal ore deposition, radioactive isotope geochemistry, stable isotope geochemistry, surface sorption geochemistry, chemical kinetics, organic geochemistry and atmospheric chemistry are also undertaken within this field. This book contains some path-breaking studies in the field of geochemistry. The topics covered herein deal with the core subjects of geochemistry. This book will provide comprehensive knowledge to the readers.