The feldspars form the most abundant group of minerals in the crust of the Earth and Moon and also occur in many meteo rites. They playa fundamental role in all rock-forming processes at shallow depths, but are rare or absent from the upper mantle. Their detailed study is thus essential for the understan ding of such varied processes as magma genesis and differentia tion, metamorphism, al teration, erosion and sedimentation. This interest is show by the fact that two previous NATO Advanced Study Institutes on feldspars were held in Oslo in 1962 and in Manchester in 1972. The feldspars are particularly sui table for detailed studies, as they have very simple chemistry and develop some of the most complex microstructures known. The microstructures are often slow to form but are easily preserved, so that they are potentially extremely informative about the geological history of the rocks in which they occur. Furthermore, their study involves physical and chemical methods of increasing sophistication so that the results obtained are not always immediately understandable to research workers outside the field of modern mineralogy. Progress in knowledge about feldspars is probably slower in penetrating the fields of petrology and geochemistry than that on other mineral groups. For these reasons among others, i~ was particularly appropriate to hold a third NATO ASI on feldspars approximately ten years after the last one.

GEOLOGICAL FIELD TECHNIQUES The understanding of Earth processes and environments over geological time is highly dependent upon both the experience that can only be gained through doing fieldwork, and the collection of reliable data and appropriate samples in the field. This textbook explains the main data gathering techniques used by geologists in the field and the reasons for these, with emphasis throughout on how to make effective field observations and record these in suitable formats. Equal weight is given to assembling field observations from igneous, metamorphic and sedimentary rock types. There are also substantial chapters on producing a field notebook, collecting structural information, recording fossil data and constructing geological maps. Geological Field Techniques is designed for students, amateur enthusiasts and professionals who have a background in geology and wish to collect field data on rocks and geological features. Teaching aspects of this textbook include: step-by-step guides to essential practical skills such as using a compass-clinometer, making a geological map and drawing a field sketch; tricks of the trade, checklists, flow charts and short worked examples; over 200 illustrations of a wide range of field notes, maps and geological features; appendices with the commonly used rock description and classification diagrams; a supporting website hosted by Wiley-Blackwell is available at www.wiley.com/go/coe/geology