The worldwide acceptance of the first edition of this book encouraged me to extensively revise and extend the second edition. The book was of value to readers of widely ranging interests as demonstrated by the letters received from scientists, students, mining engineers, editors of periodical papers and teachers.

This revision comes five years after the publication of the first edition. Many entries have been improved and now include new data. In total it includes about 25 000 entries, 1 500 graphic figures and 42 tables.

The first edition was criticized by readers who felt that some entries were not related to respective materials: but I would like to emphasize that many minerals are described in the form of references necessary for determining other gemstone materials.

In this edition chapters on light, color and colorant are dealt with in more depth, a large section introduces new terms applying to these areas.

If you have criticisms or suggestions please feel free to contact the author.

The McGraw-Hill Dictionary of Geology and Mineralogy provides a compendium of more than 9000 terms that are central to a broad range of geological sciences and related fields. The coverage in this Second Edition is focused on the areas of geochemistry, geology, geophysics, mineralogy, paleobotany, paleontology, and petrology, with new terms added and others revised as necessary.

Geology deals with the solid earth and the processes that formed and modified it as it evolved Related disciplines include the study of the physics of the earth (geophysics); earth chemistry, composition, and chemical changes (geochemistry); the composition, properties, and structure of minerals (mineralogy); the description, classification, origin, and evolution of rocks (petrology); and the study of ancient life (paleontology).

This work is the result of contributions from 52 active researchers in geophysics, astrophysics and astronomy. We have followed a philosophy of directness and simplicity, while still allowing contributors flexibility to expand in their own areas of expertise. They are cited in the contributors’ list, but I take this opportunity to thank the contributors for their efforts and their patience. The subject areas of this dictionary at the time of this writing are among the most active of the physical sciences. Astrophysics and astronomy are enjoying a new golden era, with remarkable observations in new wave bands (γ -rays, X-rays, infrared, radio) and in new fields: neutrino and (soon) gravitational wave astronomy.

The North American portion of the Cordilleran orogen extends continuously from Alaska to southern Mexico, and from east to west over much of its length the orogen comprises an easterly vergent fold-thrust belt, a complexly deformed metamorphic hinterland that collapsed gravitationally, and an interlaced mosaic of exotic terranes. Although most models for the development of the Cordilleran orogen invoke Late Jurassic–Cretaceous intraplate, backarc shortening above an eastwardly dipping subduction zone, a simple collisional model in which the leading edge of North America was subducted to the west, beneath a segmented, arc-bearing microcontinent, better fi ts the data.