For this completely new edition of Rock-Forming Minerals we have maintained the general principles and organization adopted for the first edition. The past twenty years, however, have seen an enormous expansion in activity in the Earth Sciences as a whole, and the subjects of Mineralogy and Petrology have certainly not been exceptions. The terms 'literature explosion* and 'exponential growth', although almost cliches, nevertheless are very apt in the present context. Not only have the numbers of researchers and their outputs increased, but exceptional growth has occurred in three particular fields: electron microprobe analysis, experimental petrology, and the determination of crystal structures.
The facility of rapid and accurate electron probe analysis has replaced to a great extent the more laborious chemical and optical analytical methods, giving many more reliable analyses for each mineral and enabling researchers to examine more specimens and to complete a wider range of studies in a shorter time. The availability of more well-analysed material has also led to much more significant discussion of chemical variations and their relationships with crystal structure, physical properties and, most of all, parageneses. The important phenomena of fine-scale intergrowths (exsolution, etc.) and of chemical zoning have also been much more readily investigated using electron probe and other electron-optical methods.
The study of phase equilibria at elevated pressures and temperatures has continued apace, so that the cumulative number of systems which need to be described has grown. In addition, much wider ranges of pressure and temperature have become accessible with improved techniques. At the same time, there has been a growth in the determination of thermodynamic properties of minerals, and in the experimental and theoretical approaches to element distribution within and between minerals.
The advent and growing use of automatic single-crystal diffractometers has made it possible to determine crystal structures much more quickly, so that whereas there was hitherto perhaps one published structure for a mineral or even for a mineral group, now there can be structure determinations for a mineral at each of several chemical compositions, and at a number of different temperatures.
The above, and other growth areas in mineralogy, have led to the fact that in this new edition the average number of pages devoted to each mineral is about three times that for the first edition. The extent of growth is indicated also by the list of references for each mineral which for this volume we have attempted to bring up to date to 1979, and the early months of 1981.
