Statistical evaluations of exploration data are the basis for decisions to be made at various stages of an exploration project. In contrast to other geostatistical books, Statistical Evaluations in Exploration for Mineral Deposits focuses not only on theory, but examples are also given, frequently originating from experience in mineral exploration by the author who worked worldwide for a mining company. Together with its companion volume, Economic Evaluations in Exploration, the book illustrates methods used in exploration campaigns and mining activities. It is intended as a vademecum for geologists who are forced to make quick decisions regarding an exploration project. It also addresses scientists and students involved in teaching or in mineral economic evaluations, recommendations or decisions.

This book represents the proceedings of the 9th written by a very active group of physicists at Kongsberg seminar, held at the Norwegian Mining the University of Oslo - physicists interested in Museum located in the city of Kongsberg about complex systems in general and geo-like systems 70 km Southwest of Oslo. The Kongsberg district in particular. is known for numerous Permian vein deposits of The content of the book is organized into three native silver, and mining activity in the area lasted major parts following the introductory chapter. for more than 300 years, finally ceasing in 1957. Chapters 2 to 7 primarily treat the role of fluids The previous eight Kongsberg seminars were in specific geological environments, ranging from focused on ore-forming processes and all of these sedimentary basins (Chapters 2-3) to contact were organized by Professor Arne Bj0rlykke, now metamorphic/hydrothermal scenarios (Chapters director of the Norwegian Geological Survey. 4-5) and regional metamorphic settings (Chapters Since process-orientated research tends to break 6-7). The following four chapters (8-11) focus down the traditional barriers between the different on various properties of fluid-rock systems that geological disciplines, this seminar has always are critical in controlling flow and transport been a meeting point for people with a variety through rocks. These include: mineral solubility of geological backgrounds.

Identificationof rock-forming minerals in thin section is a key skill needed by all earth science students and practising geologists. This translation of the completely revised and updated German second edition (by Leonore Hoke, Institute of Geological and Nuclear Sciences, New Zealand) provides a comprehensive guide to identifying 140 of the most important rock-forming mineral species. The book is divided into three main parts. Part A is a practical guide to the fundamentals of crystal optics, polarization microscopy and the practical use of microscopes. Part B gives a detailed description of the characteristic optical features, special features, and the paragenesis of the most common rock-forming minerals. This well-illustrated part is divided into opaque minerals, isotropic, uniaxial and optical biaxial mineral groups. Part C contains identification tables for the minerals and diagrams showing the international classification of magmatic rocks, as well as a colour plate section showing crystal forms of minerals. The book will provide an invaluable guide to all undergraduate earth scientists, as well as to professional geologists requiring an overview of mineral identification in thin section.

This book consists of a collection of papers presented at the NATO Advanced Research Workshop (ARW) on "Crust/mantle Recycl ing at Convergence Zones," held in Antalya, Turkey, between May 25 to 29, 1987. The workshop was attended by 36 earth scientists from ten countries and 28 papers were presented. Crust/mantle recycling is one of the most fundamental processes in the Earth. The study and understanding of this process requires the consideration of the Earth as a whole system including the atmosphere, the hydrosphere and the core, as well as the crust and the mantle; effective interdisciplinary collaboration is therefore essential to our progress. The Antalya ARW gave us the opportunity to assemble key specialists from relevant branches of the earth sciences and to address our state of knowledge. This ARW proved to be very useful in attaining an interdisciplinary, mutual understanding among specialists from diverse fields such as isotope and trace element geochemistry, mineral physics, theoretical geophysics, seismology, experimental petrology, and structural geology.

The collection of papers in this volume is a direct result of the Society of Economic Paleontologists and Mineralogists Research Symposium on "Thermal History of Sedimentary Basins: Methods and Case Histories" held as part of the American Association of Petroleum Geologists Annual Convention in New Orleans in March 1985. The original goal of the sym posium was to provide a forum where specialists from a variety of dis ciplines could present their views of methods that can be used to study the thermal history of a sedimentary basin or an important portion of a basin. An explicit part of that goal was to illustrate each method by presentation of a case history application. The original goal is addressed by the chapters in this volume, each of which emphasizes a somewhat different approach and gives field data in one way or another to illustrate the practical useful ness ofthe method. The significance of our relative ignorance of the thermal conductivities of sedimentary rocks, especially shales, in efforts to understand or model sedimentary basin thermal histories and maturation levels is a major thrust of the chapter by Blackwell and Steele. Creaney focuses on variations in kerogen composition in source rocks of different depositional environments and the degree to which these chem- . ically distinct kerogens respond differently to progressive burial heating."

We have used in Vol.2 the same structural scheme similar they are organized alphabetically, just for as used in Vol. 1. convenience in consulting.The alphabetical order We used as the list of minerals the reference is provisional, it is not an important aspect of the book Mineral Reference Manual by Nickel and classification, and willtend to disappear. Nichols, edited by Van Nostrand Reinhold, New In Vol. 1 some condensed model sheets were York, 1991, and we first organized the minerals by presented to illustrate the simplicityof the patterns chemical formulas, from the simpler to the more of the packing layers of the A, AmB and ApBqC n r complex (Tables 73 to 172), as presented on page close-packed minerals (Tables lL to 17Lof Vol.1). 1of Vol.1.The results of the structural studywere The aim was to stimulate the complete systematic ordered by structural formulas (Tables 27S to derivation of the simple mineral close-packed 59S). Then we summarized the classified structure structures, as was tried by the author (Lima-de- types (not including the tentatively classified) in Faria (1965) Zeit. Krist., 122, 359-374). In Vol. 2 Tables 60S to 61S. Finally we presented some the layers are more complex and the correspond- global results (Tables 62S and 63S). ing condensed models sheets were not included. In certain cases the general chemical and the The reader should refer to the book Structural structural formulas may be difficult to compare.

Acknowledgements xix pioneering workers on igneous layering in Greenland xx Wbrkshop participants xxii Henning Sfl!rensen, University of Copenhagen, Dermark. Latte Melchior Larsen, Geological SUrvey of Greenland, Copenhagen, Dermark. Abstract 1 1 * Introduction 1 1. 1 The agpaitic rocks of the Ilimaussaq intrusion 3 2. Igneous layering in the Ilimaussaq intrusion 4 3. Mineralogy of the layered kakortokite series 15 4. Chemistry of the layered kakortokite series 19 5. Origin of the kakortokite layering 20 5. 1 Discussion 22 6. Conclusion 25 References 26 2. I. AYERn";r CCMPl\CTIOO NID PCBJ. "--MN}tATIC ~ IN '!HE KLOKKEN INTRUSIOO 29 Ian Parsons and SUsanne M. Becker, University of Aberdeen, U. K. Abstract 29 1. Introduction 30 2. Age of the intrusion 31 3. General structure and mineral variation 31 vi TABLE OF CONTENTS 3. 1 Nomenclature of rock types 31 3. 2 Bulk chemical and modal variation 36 4. The contacts and wall-rocks 37 4. 1 Guter contact 37 4. 2 The gabbro sheath 37 4. 3 The unlaminated syenite sheath 39 4. 4 The gabbro-syenite transition 41 5. The layered series 43 5. 1 General relationships 43 5. 2 Granular syenites 43 5. 2. 1 Structure and cryptic variation 43 5. 2. 2 Origin of granular layers 46 5. 2. 3 Trace elements and chamber dlinensions 47 5. 3 Laminated syenites 48 5. 3. 1 General features 48 5. 3. 2 Mineral layering 51 5. 3.

During the past few years there has been a marked increase in the use of advanced chemical methods in studies of soil and clay mineral systems, but only a relatively small number of soil and clay scientists have become intimately associ ated and acquainted with these new techniques. Perhaps the most important obstacles to technology transfer in this area are: 1) many soil and clay chemists have had insufficient opportunities to explore in depth the working principles of more recent spectroscopic developments, and therefore are unable to exploit the vast wealth of information that is available through the application of such ad vanced technology to soil chemical research; and 2) the necessary equipment gen erally is unavailable unless collaborative projects are undertaken with chemists and physicists who already have the instruments. The objective of the NATO Advanced Study Institute held at the University of Illinois from July 23 to August 4, 1979, was to partially alleviate these obstacles. This volume, which is an extensively edited and reviewed version of the proceedings of that Advanced Study Institute, is an essential aspect of that purpose. Herein are summarized the theory and most current applications of six different spectroscopic methods to soil and/or clay mineral systems. The instrumental methods examined are Mossbauer, neutron scattering, x-ray photoelectron (XPS, ESCA), nuclear magnetic resonance (NMR), electron spin resonance (ESR, EPR), and photoacoustic spectroscopy. Contributing authors were also lecturers at the Advanced Study Institute, and are each well known and respected authorities in their respective disciplines."

After the spectacular successes of the 1960's and 1970's, the mineral exploration business is at a crossroads, facing uncertain t: imes in the decades ahead. This situation requires a re-thinking of the philosophy guiding mineral exploration if it is to emulate its recent performance. The ma: i. n argument of a previous volume titled "Designing Opt: lmal Strategies for Mineral Exploration," published in 1985 by Plenum Publishing Corporation of New York, is that a possible answer to the challenge facing mineral explorationists lies in the philosophy of opt: irn1zation. This new approach should help exploration staff make the best achievable use of the sophisticated and costly technology which is presently available for the detection of ore deposits. The main emphasis of the present volume is placed on the mathematical and computational aspects of the opt: irn1zation of mineral exploration. The seven chapters making up the ma: i. n body of the book are devoted to the description and application of various types of computerized geomathematical models which underpin the optimization of the mineral exploration sequence. The topics covered include: (a) the opt: lmal selection of ore deposit types and regions of search, as well as prospecting areas within the regions (Chapters 2, 3, 4, 6), (b) the designing of airborne and ground field programs for the opt: lmal coverage of prospecting areas (Chapters 2, 3, 4), (c) delineation and evaluation of exploration targets within prospecting areas by means of opt: irn1zed models (Chapter 5).

In the extensive field of earth sciences, with its many subdisciplines, the trans fer of knowledge is primarily established via personal communication, during meetings, by reading journal articles, or by consulting books. Because more information is available than can be assimilated, it is necessary for the individual to search selectively. Books take more time from the inception of an idea until publication than any of the other means of communication men tioned. As a consequence, their function is somewhat different. Many good books are a compilation of up to date knowledge and serve as reference or instruction manuals. Some books are a collection of previously published papers dealing with a certain topic, while others may basically provide large sets of data or examples. The Frontiers in Sedimentary Geology series was established both for stu dents and practicing earth scientists who wish to either stay abreast of the most recent ideas or developments or to become familiar with an important topic in the field of sedimentary geology. The series attempts to deal with sub jects that are in the forefront of both scientific and economic interest. The treatment of a subject in an individual volume should be a combination of topi cal, regional, and interdisciplinary approaches. Although these three terms can be defined separately, in reality they should flow into each other. A topical treatment should relate to a major category of sedimentary geology.

Mine Safety combines detailed information on safety in mining with methods and mathematics that can be used to preserve human life.

By compiling various recent research results and data into one volume, Mine Safety eliminates the need to consult many diverse sources in order to obtain vital information. Chapters cover a broad range of topics, including: human factors and error in mine safety, mining equipment safety, safety in offshore industry and programmable electronic mining system safety.

They are written in such a manner that the reader requires no previous knowledge to understand their contents. Examples and solutions are given at appropriate places, and there are numerous problems to test the reader's comprehension.

Mine Safety will prove useful for many individuals, including engineering and safety professionals working in the mining industry, researchers, instructors, and undergraduate and graduate students in the field of mining engineering.

Granite petrology has achieved significant progress since Tuttle and Bowen (1958) wrote the monograph on the Origin of granite in the light of experimental studies in the system NaAISi308-KAISi308-SiOrH20. Since then, the compo nents CaAI Si 0, FeO, MgO, and excess alumina have 2 2 s been added to the pure system Ab-Or-Qz-H 0 in order to 2 include plagioclase and common mafic minerals in the inves tigations. In addition to synthetic systems, natural rocks have been used as starting materials, and other fluid compo or substituted for water. nents have been added to There are many new data concerning properties of melts and magmas, dehydration melting of synthetic and natural rocks, and phase relationships at H 0-undersaturated con 2 ditions. We found it useful and necessary to summarize the available information in this volume, and an effort has been made to present up-to-date data on various aspects of gran ite petrology. Most parts of the manuscript were reviewed by John Clemens, Peter Nabelek, and Alan White. Their friendly help and suggestions improved it considerably. Some chap ters of this volume benefited from critical review by William Brown, Bruno Scaillet, and Robert Linnen. Peter Wyllie pro vided us with reprints and many critical and useful sugges tions. Jagmohan Singh improved the English considerably."

Many people have contributed to the production of this book, and I wish to acknowledge the following colleagues who have, over the past 15 years, contributed much discussion, preprints, thin sections, rock samples, and unpublished and/or difficult-to- obtain information: Steve Bergman, Roger Clement, Howard Coopersmith, Barry Dawson, Alan Edgar, Tony Erlank, Steve Haggerty, Barry Hawthorne, Bram Janse, Viktoria Komilova, Sergei Kostrovitskii, Henry Meyer, Peter Nixon, Nick Rock, Mike Skinner, Patricia Sheahan, Simon Shee, Barbara Scott Smith, Andy Spriggs, Ken Tainton, Larry Taylor, Nikolai Vladykin, Allan Woolley, and Peter Wyllie. Special thanks go to Henry Meyer, for providing many hours of microprobe time at Purdue University, and to Mike Skinner, for samples and the opportunity to examine the Anglo-American Research Laboratory collection of orangeites. Particular thanks are expressed to Ken Tainton for permission to quote data from his Ph.D. thesis. Particular gratitude is expressed to Sam Spivak for drafting and photographic work and to Anne Hammond for preparing many polished thin sections of these difficult rocks. Their dedication, skills, and attention to detail are greatly appreciated by the author. Others from Lakehead University who helped materially during the production of this work include Reino Viitala (thin sections), Alan MacKenzie (electron microscopy), and Shelley Moogk-Pickard (trace element analysis). Carl Hager is thanked for assistance in using the Purdue microprobe.

This monograph was begun with two objectives in mind. The first was to provide a review of research involving the application of neodymium isotopic measurements to pro blems in earth science. In the process of organizing to do this, I realized that the research in this field had produced a need for an updated review of the underlying paradigms. This need had arisen because of the special properties of the samarium-neodymium isotopic system, and because the research had transgressed the traditional boundaries be tween the subfields of earth science. Without such a review, the significance of the results seemed likely to remain un necessarily obscure to interested scientists from related disciplines. Consequently, the second objective became the provision of a theoretical framework for the application of neodymium isotopic studies. Much of what this contains is not new, but it is drawn together here for the first time. At the time the writing was initiated, the literature of the field was still relatively limited. Over the past 5 years it has grown enormously. Considering the rate at which the writing progressed, it became clear that this could not be a fully up-to-date review and still reach completion. The selection of material for the review sections is biased toward earlier studies. Part I presents most of the background information."

During the last thirty years profound developments in expe- rimental techniques to measure high temperature and pressu- res and thermodynamic properties of minerals have occurred. This technical development has been matched by an increased sophistication in applying theoretical methods to obtain new data or improve the quality of existing data. Using these newtechniques, Assessed Thermodynamic Data on Oxides and Silicates represents the successful attempt of the authors to develop an internally systematized data base which satis- fies the constraints of calorimetric measurements, phase equilibrium data, measured thermophysical properties of a phase, and heat capacities and entropies estimated from lat- tice vibrational models.

The reserves, or extractable fraction, of the fuel-mineral endowment are sufficient to supply the bulk of the world's energy requirements for the immediately forseeable future-well into the next century according to even the most pessimistic predictions. But increasingly sophisticated exploration concepts and technology must be employed to maintain and, if possible, add to the reserve base. Most of the world's fuel-mineral resources are in sedimentary rocks. Any procedure or concept that helps describe, under stand, and predict the external geometry and internal attributes of major sedimentary units can therefore contribute to discovery and recovery of coal, uranium, and petroleum. While conceding the desirability of renewable and nonpolluting energy supply from gravitational, wind, or solar sources, the widespread deployment of these systems lies far in the future-thus the continued commercial emphasis on conventional nonrenewable fuel mineral resources, even though their relative significance will fluctuate with time. For example, a decade ago the progilostications for uranium were uniformly optimistic. But in the early 1980s the uranium picture is quite sombre, although unlikely to remain permanently depressed. Whether uranium soars to the heights of early expectations remains to be seen. Problems of waste disposal and public acceptance persist. Fusion reactors may ultimately eliminate the need for uranium in power generation, but for the next few decades there will be continued demand for uranium to fuel existing power plants and those that come on stream. This book is, to some extent, a hybrid."

Few knowledgeable people would deny that the field of mineral exploration is facing some difficult times in the foreseeable future. Among the woes, we can cite a worldwide economic uneasiness reflected by sluggish and at times widely fluctuating metal prices, global financial uncertainties, and relentless pressures on costs despite a substantial slowing down of the rate of inflation. Furthermore, management is forced to tum to more sophisticated and expensive technologies and to look farther afield to more remote regions, as the better quality and more easily accessible ore deposits have now been revealed. This rather gloomy outlook should persuade explorationists to cast about for a new philosophy with which to guide mineral exploration through the challenging decades ahead. Once already, in the early 1960s, a call for change had been heard (Ref. 30 in Chapter 1), when it became obvious that the prospecting methods of yesteryear, so successful in the past, could not keep up with the rapidly growing demand for minerals of the postwar period. The answer, a massive introduction of sophisticated geophysical and geochemical technologies backed by new geo logical models, proved spectacularly successful throughout the 1960s and the 1970s. But for both economic and technological reasons, the brisk pace of the last two decades has considerably slowed down in the early 1980s, as if a new threshold has been reached."

Metals in the hydrological cycle represent a very broad subject covering all parts of the geological cycle. The present version of this book, therefore, would not have been possible without the comments and suggestions for improvement on draft ver- sions of the various chapters by a large number of colleagues. We wish to express our gratitude to: P.A. Cawse (AERE, UK), J.N. Galloway (University of Virginia, USA) and S.E. Lindberg (Oak Ridge National Labo- ratory, USA) for reviewing the chapter on atmospheric trace metals. G. Batley (CSIRO, Australia) and B.T. Hart (Chisholm In- stitute of Technology, Australia) for reviewing the chapter on speciation of dissolved metals. E.K. Duursma (Delta Institute, The Netherlands), J.M. Bewers and P.H. Yeats (Bedford Institute of Oceanography, Canada) and D. Eisma (Netherlands Institute for Sea Re- search, the Netherlands) for reviewing the chapter on estuaries. P. Baccini (EAWAG, Switzerland) and W. Davison (Fresh- water Biological Association, UK) for reviewing the chapter on lakes. E.T. Degens (University of Hamburg, W-Germany) for re- viewing the chapter on the oceans, and J.P. Al (Public Works Department, The Netherlands) for reviewing most of the indi- vidual chapters. Without the collaboration of these colleagues this book would not have been possible in its present form.

As natural minerals, silica and silicates constitute by far the largest part of the earth's crust and mantle. They are equally important as raw materials and as mass produced items. For this reason they have been the subject of scientific research by geoscientists as well as by applied scientists in cement, ceramic, glass, and other industries. Moreover, intensive fun damental research on silicates has been carried out for many years because silicates are, due to their enormous variability, ideally suited for the study of general chemical and crystallographic principles. Several excellent books on mineralogy and cement, ceramics, glass, etc. give brief, usually descriptive synopses of the structure of silicates, but do not contain detailed discussions of their structural chemistry. A number of monographs on special groups of silicates, such as the micas and clay min erals, amphiboles, feldspars, and zeolites have been published which con tain more crystal chemical information. However, no modern text has been published which is devoted to the structural chemistry of silicates as a whole. Within the last 2 decades experimental and theoretical methods have been so much improved to the extent that not only have a large number of silicate structures been accurately determined, but also a better under standing has been obtained of the correlation between the chemical composition of a silicate and its structure. Therefore, the time has been reached when a modern review of the structural chemistry of silicates has become necessary."

Komatiites erupted billions of years ago as pulsating streams of white-hot lava. Their unusual chemical compositions and exceptionally high formation temperatures produced highly fluid lava that crystallized as spectacular layered flows. Investigation of the extreme conditions in which komatiites formed provides important evidence about the thermal and chemical evolution of the planet, and the nature of the Precambrian mantle. This monograph, written by three experts with long experience in the field, presents a complete account of the characteristics of komatiites including their volcanic structures, textures, mineralogy and chemical compositions. Models for their formation and eruption are evaluated (including the anhydrous vs. hydrous magmas controversy). A chapter is also devoted to the valuable nickel and copper ore deposits found in komatiites. Komatiite is a key reference for researchers and advanced students interested in petrology, Archaean geology, economic geology, and broader questions about the evolution of the Earth's crust and mantle.

Phase transitions in minerals are of interest to a wide spectrum of scientists - geolo- gists, mineralogists, solid state chemists, and physicists. We have now reached the point where mean field theory or Landau Theory of phase transitions as a function of temperature, pressure, or chemical composition can be usefully applied to natural materials, resulting in an improved understanding of the thermodynamics of signifi- cant constituents of the earth. Given the chemical complexity of so many silicate solid solutions, there are two distinct approaches to the problems posed by common minerals: one is to con- centrate on model compounds which could be synthetic analogs or natural end- members; the other is to work on typical minerals, with all the disorder and inhomogeneity that this implies. Model compounds provide the elements needed to build up a realistic understanding of the thermodynamic behavior of natural inor- ganic materials in all their complexity. In the first part of the book, a number of papers are devoted to structural phase transitions in quartz, Na-and Ca-feldspars, MgSi0 perovskite, and PbI , where Landau Theory and lattice and molecular 3 2 dynamics have been used to explain or predict thermodynamic behavior. A different thermodynamic approach has been used to understand phase separation and atomic ordering in solid solutions such as olivines, pyroxenes, rhombohedral carbonates and oxides. E. Salje (Chapter 1) applies the Landau Theory for the second-order phase transi- tion to the feldspar end-members albite, NaAlSi0 , and anorthite, CaAlSi0 .

The idea for a book on anorthosites came to me in January of 1986 while returning to Houston after holiday festivities in Dallas. The original idea was a review paper on anorthosites, but by the time I reached Houston, the subject material I contemplated induding was obviously too extensive for a single paper. The Director of the Lunar and Planetary Institute, Kevin Burke, was receptive to the idea of a book, and suggested that I contact Peter Wyllie, who serves as Editor of the Springer-Verlag series Minerals and Rocks. This effort, which I originally expected would take about a year, has taken nearly 6. I have many excuses- indolence, moving to another continent, other commitments, etc.-but the basic truth is that writing a book is much larger an undertaking than can be anticipated. Many people are aware of this, and I was duly forewarned. . But why write a book on anorthosites? This is a very good question, which I have considered from many angles. One rationale can be expressed in terms of a comparison between anorthosite and basalt. A first-order understanding of basalt genesis has been extant for many years. By contrast, there is little agreement about the origin of anorthosite. There are good reasons for studying and writing about basalt: it is the most abundant rock type on the Earth's surface, and is also plentiful on the surfaces of the other terrestrial planets.

Phenomenal new observations from Earth-based telescopes and Mars-based orbiters, landers, and rovers have dramatically advanced our understanding of the past environments on Mars. These include the first global-scale infrared and reflectance spectroscopic maps of the surface, leading to the discovery of key minerals indicative of specific past climate conditions; the discovery of large reservoirs of subsurface water ice; and the detailed in situ roving investigations of three new landing sites. This an important, new overview of the compositional and mineralogic properties of Mars since the last major study published in 1992. An exciting resource for all researchers and students in planetary science, astronomy, space exploration, planetary geology, and planetary geochemistry where specialized terms are explained to be easily understood by all who are just entering the field.

At last geochemists are offered one comprehensive reference book which gives the Eh-pH diagrams for 75 elements found in the earth's surface environment, including transuranic and other radioactive species. For each of these newly calculated diagrams short explanatory texts are added. For the first time the primary elements are considered in water with metal, sulfur, carbon, and other species as appropriate. Furthermore, based on these figures and up-to-date thermodynamic data presented in this reference, researchers can predict the behavior of elements in the surface environment. Geoscientists, chemists and environmental agencies will also benefit from several brief texts on the importance of various elements to problems of radioactive waste disposal.

33 14. 3. 5 REE between Plagioclase and Aqueous Fluid 0 Cullers et al. (1973) measured the distribution of REE at 850 C and 750 bars pressure between a natural plagioclase, An, and gaseous water. The rare earths 65 favored the plagioclase by a factor which varies from about 25 for Ce to 10 for Lu. Data were also obtained for forsterite, diopside, enstatite and two rhyolite glasses, on the one hand, and water on the other hand, thereby permitting estimation of the partition coefficients between all pairs of phases. 14. 4 Chemical Substitution in Natural Feldspars 14. 4. 1 Introduction It is quite impracticable to give all the data on chemical substitution in natural feldspars: indeed many of the details are significant only to some particular pegmatite or rock body. As far as possible, emphasis is placed on features of general interest to crystal chemists and to petrologists. Ironically the well established features can be described more easily than the uncertain ones, and unfortunately it is necessary to use valuable space on data of dubious value. The bibliography is fairly complete, but it was impracticable to locate all data, especially those in obscure journals. Each reference is followed by a list of the elements referred to in the paper, thereby permitting a reader to compile a fairly compre hensive set of references on any chosen element. Not all papers are mentioned in the text. The book on Geochemistry and Mineralogy of Rare Elements, etc."