This text deals with concepts in the genesis of hydrothermal ore deposits and describes a number of key mineral deposits worldwide. It looks at the relationship between hydrothermal mineral deposits and global tectonics in order to understand better the natural ore building processes. In three parts, (A) the nature and types of hydrothermal systems, (B) its relationship to global tectonics and related hydrothermal mineral deposits, and (C) hydrothermal processes and related mineral deposits are discussed in detail.