Petrology is the branch of geology that studies the origin, composition, distribution and structure of rocks. Petrology utilizes the classical fields of mineralogy, petrography, optical mineralogy, and chemical analyses to describe the composition and texture of rocks. Modern petrologists also include the principles of geochemistry and geophysics through the studies of geochemical trends and cycles and the use of thermodynamic data and experiments to better understand the origins of rocks. Some observers believe that oil shales will be mined and utilized as a major source of fuel in the future as petroleum and natural gas supplies inevitably dwindle. This valuable book is designed to give students a balanced and comprehensive coverage of these new advances, as well as a firm grounding in the classical aspects of igneous and metamorphic petrology.