An Introduction to the Rock-Forming Minerals

In this edition of Introduction to the Rock-Forming Minerals, most of the commonly occurring minerals of igneous, metamorphic and sedimentary rocks are discussed in terms of structure, chemistry, optical and other physical properties, distinguishing features and paragenesis. Important correlations between these aspects of mineralogy are emphasized wherever possible. The content of each section has been updated where needed in the light of published research over the 21 years between editions. Tables of over 200 chemical analyses and formulae are included and a number of older entries have been replaced by more recent examples. Major new features include: Entirely new views of crystal structures in perspective using CrystalMaker colour images; CrystalViewer interactive CD with >100 mineral structures included; Over 60 colour photographs of minerals in thin sections of rocks under the petrological microscope; Considerably expanded treatment of feldspar and zeolite minerals; Mineral identification table based on birefringence and listing other properties; and Colour strip with appropriate interference colours and birefringences for the main rock-forming minerals. This book will be useful to undergraduate students of mineralogy, petrology and geochemistry, especially those at third or fourth year, engaged in more advanced courses or specialized projects, and also as a reference work for students for ‘Masters’ degrees by taught courses or research. For doctorate students, and research workers in the Earth Sciences as well as those in Materials Science and other related disciplines, this work can be useful as a condensed version of the very extensive treatment presented in the volumes of the DHZ Series ‘Rock-Forming Minerals’, second edition.
Abstract
Kyanite has a structure in which the oxygen atoms are arranged in a slightly distorted close-packed cubic array. As in andalusite and sillimanite, there are chains of Al-O octahedra (Al coloured green in Fig. 29) and these are linked together by the remaining Si, Al and O atoms, Si being coordinated by four oxygen atoms, and Al by six oxygen atoms. The Si-O tetrahedra do not share corners with other Si-O tetrahedra, although they may appear to do so because of overlap in projection. The volumes of the unit cell of the three Al2SiO5 polymorphs and their molar volumes are as listed in Table 6, confirming that kyanite has the lowest specific volume and will thus be the polymorph favoured by highest pressure conditions.