This major revision takes place 38 years after the publication of the first edition. This volume in the second edition of the series Rock-forming Minerals is devoted entirely to the feldspar minerals. The text has been completely re-written and very much expanded,incorporating the advances in knowledge and understanding arising from the new and improved techniques for the study of minerals that have developed over the decades between editions. The authors have maintained the general approach used in the other volumes, summarising important research results and presenting them in an organised fashion. Readership: Rock-forming Minerals is a standard reference work for professionals in mineralogy, petrology and geochemistry, as well as having a wide appeal as a reference work for postgraduate research students and research workers in related fields.