Thermodynamics of Crystalline Solutions

Minerals are crystalline solutions showing a very wide range of chemical and structural variations. As opposed to molecular solutions, in which the molecules mix with each other, crystalline solutions are characterized by the mixing of ions (or atoms) on a variety of crystal structure sites. A comprehensive treatment of the thermodynamics of crystalline solutions, a rather daunting task, is beyond the scope of this book. In order to do justice to this subject within a single chapter, we shall concentrate on a few selected topics. Our treatment focuses on the thermodynamics of simple crystalline solutions (defined below). Its extension to complex crystalline solutions will be somewhat cursory, and order-disorder phenomena, observed in numerous minerals, will be barely touched. Readers interested in such topics may find the monograph by Ganguly and Saxena (1987) helpful.