Thermodynamic treatment of mineral equilibria, a topic central to mineralogical thermodynamics, can be traced back to the tum of the century, when J. H. Van't Hoff and his associates pioneered in applying thermodynamics to the mineral assemblages observed in the Stassfurt salt deposit. Although other renowned researchers joined forces to develop the subject - H. E. Boeke even tried to popularize it by giving an overview of the early developments in his "Grundlagen der physikalisch-chemischen Petrographie", Berlin, 1915 - it remained, on the whole, an esoteric subject for the majority of the contemporary geological community. Seen that way, mineralogical thermodynamics came of age during the last four decades, and evolved very rapidly into a mainstream discipline of geochemistry. It has contributed enormously to our understanding of the phase equilibria of mineral systems, and has helped put mineralogy and petrology on a firm quantitative basis. In the wake of these developments, academic curricula now require the students of geology to take a course in basic thermodynamics, traditionally offered by the departments of chemistry. Building on that foundation, a supplementary course is generally offered to familiarize the students with diverse mineralogical applications of thermo dynamics. This book draws from the author's experience in giving such a course, and has been tailored to cater to those who have had a previous exposure to the basic concepts of chemical thermodynamics.