Intended as a reference for the academically-oriented geologist as well as the practising economic geologist, this book is concerned with the study of skarn deposits having anomalously high tin or tungsten contents, or both. Unlike many other books on economic geology, both economic W-Sn skarns and non-economic examples are covered, in order to enable the academically-oriented reader to grasp the full range of such deposits, and also to aid the economic geologist in distinguishing between W-Sn skarns having economic potential and those which do not.W-Sn skarns are notoriously complex, containing a wide range of textures, grain sizes, mineral assemblages, bulk compositions and structures. The lack of a sufficiently detailed data base, coupled with some unsupportable genetic models, has led to many misunderstandings and has often resulted in needless expenditure and effort on fruitless mineral exploration. Thus, the first aim of this book is simply to provide an adequate data base with sufficient references to enable an interested worker to define a skarn deposit and know where to find additional information on similar examples. To aid this, as much data as possible is presented as tables and diagrams.The second aim of the book is to show the reader how to separate skarn rocks found in W-Sn-bearing environments into those produced by metamorphic, isochemical processes (metamorphic skarns) which are uneconomic, and those produced by the introduction and exchange of components from an ore solution (ore skarn). W-Sn skarns are also separated into genetically logical subdivisions so that, if a deposit or a specific geological environment can be identified, then skarn zonation or the potential of finding specific skarn types can be predicted. This is particularly important to the practising exploration geologist because often only a small part of a skarn or only certain skarn types contain economic mineralization.In addition, the book provides an insight into how to assess where mineralogical complications may occur, especially with respect to Sn-skarns, and in which environments such complications may be expected. It also provides enough information for the reader to be able to conceptualize suitable models for W-Sn skarns based on primary data.