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 Precambrian crust of Saudi Arabia, the eastern Sudan and Egypt consists of abundant granites and granodiorites, arc-type volcanics, and well-authenticated ophiolites. The metamorphic grade is generally low. Archaean remnants are absent. In contrast, the Precambrian in the Mozambique belt in Kenya and Tanzania consists of high-grade metamorphic rocks, contains much reworked Archaean basement, and few granitic or granodioritic plutons. It is proposed that there is a transition from crust formed by successive accretion of island arc/back arc complexes in the north to products of collisions between plates carrying Archaean continental crust in the south. The collision led to Himalayan-type crustal thickening, deep erosion and isostatic uplift, exposing deep-crustal rocks. <...>

In October 1975 a Short Course on Feldspar Mineralogy was held at the Hotel Utah, Salt Lake City, in conjunction with the annual meetings of the Mineralogical Society of America. Richard A. Yund, David B. Stewart, Joseph V. Smith and Paul H. Ribbe presented workshops on x-ray single-crystal and powder diffraction methods and electron optical techniques as applied to the study of feldspars and presented eight lectures, the substance of which became the nine chapters of the first edition of Feldspar Mineralogy. That book was published by the Mineralogical Society as the second volume of its series entitled "Short Course Notes". <...>

Prior to Hubbert and Rubey's classic paper (Hubbert & Rubey 1959), which specifically recognized the role of high fluid pressures in
lowering the shear stress required to move and emplace large thrust sheets, geologists had tended to ignore the importance of fluids in crustal deformation (Fyfe et al. 1978). Much has changed in the intervening 40 years. It is now accepted that not only do fluids enable deformation but that the converse is also true, i.e. that faulting can cause fluid migration.