Nearly every mineralogy, metallurgy, chemistry, and physics textbook now contains a short section on crystallography. These abbreviated treatments can hardly be expected to present more than some of the conclusions of the science. Something was plainly needed to explain the reasoning leading to these conclusions. This book was written to supply a fuller account of the subject.

Thousands of scholars, professors, teachers, and members of the public have visited the Geological Museum Valentí Masachs, associated with the Universitat Politècnica de Catalunya (UPC) (Polytechnic University of Catalonia) in Manresa (Barcelona, Catalonia), since it opened in June 1980.

The Geological Museum Valentí Masachs is an unconventional one, very different from the traditional type. The exhibition’s main aim is to visualize the connection between human activity and planet Earth (Fig. 1).

One purpose of this book is to advance the idea that many minerals are not fixed and simple in composition. Some years ago Professor D. Jerome Fisher of the University of Chicago pointed out that the writer's Elements of Optical Mineralogy had made such a treatment available to advanced students for some years, but that no elementary textbook, in any language, presented the subject in a similar way. A result of Dr. Fisher's suggestion has been the preparation of this volume.

The oil industry has changed much since I first entered it some 30 years ago, and still more dramatically since I completed the first edition of Elements of Petroleum Geology in 1982. In the past 15 years major changes have occurred in the way in which the oil industry is organized and in how it conducts its business.
Traditionally, the leading edge of research was conducted in the laboratories of the oil companies. Now it is conducted within service companies and consultancies. Whereas traditionally the oil companies were regarded as the best employers in terms of opportunity and continuity of employment, today this is no longer true. The service companies and larger consultancies may now provide better long-term career prospects than the major oil companies.