This is the seventh edition of a book which has been for years the ''bible'' of professional and amateur gemmologists, as well as retail jewellers. Originally written by Robert Webster, an expert who dedicated most of his life to the subject and who worked in the London Gem Testing Laboratory for twenty-five years, this edition has been completely revised and updated by E. Alan Jobbins, Keeper of Minerals and Gemstones at the Geological Museum in London for thirty-five years. The first part of the book is a comprehensive glossary on all aspects of gemstones and the terms associated with them. The second part includes sections on manufactured gems, the enhancement of gem materials and on the precautions necessary for avoiding damage to gemstones and jewellery during manufacturing, repairs and cleaning. There are comprehensive sets of tables of the physical constraints needed for gem testing, of the sources of gem materials and the cuts used to demonstrate their beauty. Fifteen pages of colour photographs will assist in the identification of inclusions and there are many useful conversion tables.Acknowledged as one of the most useful reference books available, this should be the vade mecum of all gemmologists.