This book is designed to be used as an introduction to geochemistry by undergraduate and graduate chemistry and geology students as well as by those from other sciences. It summarizes the significant facts and ideas concerning the chemistry of the earth and synthesizes these data into an account of the physical and chemical evolution ol the earth. The aim of the book is to explore an intlresting, complex, and changing subject. An attempt has !'een made to cover the entire field of geochemistry. However, not alI subjects have been coveredwith equal detail becauseto properly cover the facts and theories would require a volume far too long to be suitably used as a text. Some areas of geochemical interest such as phase diagrams and ore deposits have been adopted by other courses in thc geology curriculum. and thermodynamics, a key to understanding geochemical processes, requires the depth of presentation given in physical chemistry courses. <...>

This chapter introduces rocks and petrology, the science that attempts to explain the origin and distribution of rocks. Rocks are the solid material constituting the Earth, and it is essential to know what composition the planet has. We begin with a brief review of the planetary formation process and how it determined the Earth’s composition and major divisions into core and mantle.