ALBERT

Description / Table of Contents: PREFACE Phase transformations occur in most types of materials, including ceramics, metals, polymers, diverse organic and inorganic compounds, minerals, and even crystalline viruses. They have been studied in almost all branches of science, but particularly in physics, chemistry, engineering, materials science and earth sciences. In some cases the objective has been to produce materials in which phase transformations are suppressed, to preserve the structural integrity of some engineering product, for example, while in other cases the objective is to maximise the effects of a transformation, so as to enhance properties such as superconductivity, for example. A long tradition of studying transformation processes in minerals has evolved from the need to understand the physical and thermodynamic properties of minerals in the bulk earth and in the natural environment at its surface. The processes of interest have included magnetism, ferroelasticity, ferroelectricity, atomic ordering, radiation damage, polymorphism, amorphisation and many others—in fact there are very few minerals which show no influence of transformation processes in the critical range of pressures and temperatures relevant to the earth. As in all other areas of science, an intense effort has been made to turn qualitative under-standing into quantitative description and prediction via the simultaneous development of theory, experiments and simulations. In the last few years rather fast progress has been made in this context, largely through an inter-disciplinary effort, and it seemed to us to be timely to produce a review volume for the benefit of the wider scientific community which summarises the current state of the art. The selection of transformation processes covered here is by no means comprehensive, but represents a coherent view of some of the most important processes which occur specifically in minerals. A number of the contributors have been involved in a European Union funded research network with the same theme, under the Training and Mobility of Researchers programme, which has stimulated much of the most recent progress in some of the areas covered. This support is gratefully acknowledged.

Description / Table of Contents: The first half-century of X-ray crystallography, beginning with the elucidation of the sodium chloride structure in 1914, was devoted principally to the determination of increasingly complex atomic topologies at ambient conditions. The pioneering work of the Braggs, Pauling, Wyckoff, Zachariasen and many other investigators revealed the structural details and underlying crystal chemical principles for most rock-forming minerals (see, for example, Crystallography in North America, edited by D. McLachlan and J. P. Glusker, NY, American Crystallographic Association, 1983). These studies laid the crystallographic foundation for modem mineralogy. The past three decades have seen a dramatic expansion of this traditional crystallographic role to the study of the relatively subtle variations of crystal structure as a function of temperature, pressure, or composition. Special sessions on "High temperature crystal chemistry" were first held at the Spring Meeting of the American Geophysical Union (April 19, 1972) and the Ninth International Congress of Crystallography (August 30, 1972). The Mineralogical Society of America subsequently published a special 11-paper section of American Mineralogist entitled "High Temperature Crystal Chemistry," which appeared as Volume 58, Numbers 5 and 6, Part I in July-August, 1973. The first complete three-dimensional structure refinements of minerals at high pressure were completed in the same year on calcite (Merrill and Bassett, Acta Crystallographica B31, 343-349, 1975) and on gillespite (Hazen and Burnham, American Mineralogist 59, 1166-1176, 1974). Rapid advances in the field of non-ambient crystallography prompted Hazen and Finger to prepare the monograph Comparative Crystal Chemistry: Temperature, Pressure, Composition and the Variation of Crystal Structure (New York: Wiley, 1982). At the time, only about 50 publications documenting the three-dimensional variation of crystal structures at high temperature or pressure had been published, though general crystal chemical trends were beginning to emerge. That work, though increasingly out of date, remained in print until recently as the only comprehensive overview of experimental techniques, data analysis, and results for this crystallographic sub-discipline. This Reviews in Mineralogy and Geochemistry volume was conceived as an updated version of Comparative Crystal Chemistry. A preliminary chapter outline was drafted at the Fall 1998 American Geophysical Union meeting in San Francisco by Ross Angel, Robert Downs, Larry Finger, Robert Hazen, Charles Prewitt and Nancy Ross. In a sense, this volume was seen as a "changing of the guard" in the study of crystal structures at high temperature and pressure. Larry Finger retired from the Geophysical Laboratory in July, 1999, at which time Robert Hazen had shifted his research focus to mineral-mediated organic synthesis. Many other scientists, including most of the authors in this volume, are now advancing the field by expanding the available range of temperature and pressure, increasing the precision and accuracy of structural refinements at non-ambient conditions, and studying ever more complex structures. The principal objective of this volume is to serve as a comprehensive introduction to the field of high-temperature and high-pressure crystal chemistry, both as a guide to the dramatically improved techniques and as a summary of the voluminous crystal chemical literature on minerals at high temperature and pressure. The book is largely tutorial in style and presentation, though a basic knowledge of X-ray crystallographic techniques and crystal chemical principles is assumed. The book is divided into three parts. Part I introduces crystal chemical considerations of special relevance to non-ambient crystallographic studies. Chapter 1 treats systematic trends in the variation of structural parameters, including bond distances, cation coordination, and order-disorder with temperature and pressure, while Chapter 2 considers P-V-T equation-of-state formulations relevant to x-ray structure data. Chapter 3 reviews the variation of thermal displacement parameters with temperature and pressure. Chapter 4 describes a method for producing revealing movies of structural variations with pressure, temperature or composition, and features a series of "flip-book" animations. These animations and other structural movies are also available as a supplement to this volume on the Mineralogical Society of America web site at (http://www.minsocam.orgIMSAlRimlRim41.html). Part II reviews the temperature- and pressure-variation of structures in major mineral groups. Chapter 5 presents crystal chemical systematics of high-pressure silicate structures with six-coordinated silicon. Subsequent chapters highlight temperature- and pressure variations of dense oxides (Chapter 6), orthosilicates (Chapter 7), pyroxenes and other chain silicates (Chapter 8), framework and other rigid-mode structures (Chapter 9), and carbonates (Chapter 10). Finally, the variation of hydrous phases and hydrogen bonding are reviewed in Chapter 11, while molecular solids are summarized in Chapter 12. Part III presents experimental techniques for high-temperature and high-pressure studies of single crystals (Chapters 13 and 14, respectively) and polycrystalline samples (Chapter 15). Special considerations relating to diffractometry on samples at non-ambient conditions are treated in Chapter 16. Tables in these chapters list sources for relevant hardware, including commercially available furnaces and diamond-anvil cells. Crystallographic software packages, including diffractometer operating systems, have been placed on the Mineralogical Society web site for this volume. This volume is not exhaustive and opportunities exist for additional publications that review and summarize research on other mineral groups. A significant literature on the high-temperature and high-pressure structural variation of sulfides, for example, is not covered here. Also missing from this compilation are references to a variety of studies of halides, layered oxide superconductors, metal alloys, and a number of unusual silicate structures.

Description / Table of Contents: PREFACE Sulfate is an abundant and ubiquitous component of Earth’s lithosphere and hydrosphere. Sulfate minerals represent an important component of our mineral economy, the pollution problems in our air and water, the technology for alleviating pollution, and the natural processes that affect the land we utilize. Vast quantities of gypsum are consumed in the manufacture of wallboard, and calcium sulfates are also used in sculpture in the forms of alabaster (gypsum) and papier-mâché (bassanite). For centuries, Al-sulfate minerals, or “alums,” have been used in the tanning and dyeing industries, and these sulfate minerals have also been a minor source of aluminum metal. Barite is used extensively in the petroleum industry as a weighting agent during drilling, and celestine (also known as “celestite”) is a primary source of strontium for the ceramics, metallurgical, glass, and television face-plate industries. Jarosite is a major waste product of the hydrometallurgical processing of zinc ores and is used in agriculture to reduce alkalinity in soils. At many mining sites, the extraction and processing of coal or metal-sulfide ores (largely for gold, silver, copper, lead, and zinc) produce waste materials that generate acid-sulfate waters rich in heavy metals, commonly leading to contamination of water and sediment. Concentrated waters associated with mine wastes may precipitate a variety of metal-sulfate minerals upon evaporation, oxidation, or neutralization. Some of these sulfate minerals are soluble and store metals and acidity only temporarily, whereas others are insoluble and improve water quality by removing metals from the water column. There is considerable scientific interest in the mineralogy and geochemistry of sulfate minerals in both high-temperature (igneous and hydrothermal) and low-temperature (weathering and evaporite) environments. The physical scale of processes affected by aqueous sulfate and associated minerals spans from submicroscopic reactions at mineral-water interfaces to global issues of oceanic cycling and mass balance, and even to extraterrestrial applications in the exploration of other planets and their satellites. In mineral exploration, minerals of the alunite-jarosite supergroup are recognized as key components of the advanced argillic (acid-sulfate) hydrothermal alteration assemblage, and supergene sulfate minerals can be useful guides to primary sulfide deposits. The role of soluble sulfate minerals formed from acid mine drainage (and its natural equivalent, acid rock drainage) in the storage and release of potentially toxic metals associated with wet-dry climatic cycles (on annual or other time scales) is increasingly appreciated in environmental studies of mineral deposits and of waste materials from mining and mineral processing. This volume compiles and synthesizes current information on sulfate minerals from a variety of perspectives, including crystallography, geochemical properties, geological environments of formation, thermodynamic stability relations, kinetics of formation and dissolution, and environmental aspects. The first two chapters cover crystallography (Chapter 1) and spectroscopy (Chapter 2). Environments with alkali and alkaline earth sulfates are described in the next three chapters, on evaporites (Chapter 3). barite-celestine deposits (Chapter 4), and the kinetics of precipitation and dissolution of gypsum, barite, and celestine (Chapter 5). Acidic environments are the theme for the next four chapters, which cover soluble metal salts from sulfide oxidation (Chapter 6), iron and aluminum hydroxysulfates (Chapter 7), jarosites in hydrometallugy (Chapter 8), and alunite-jarosite crystallography, thermodynamics, and geochronology (Chapter 9). The next two chapters discuss thermodynamic modeling of sulfate systems from the perspectives of predicting sulfate-mineral solubilities in waters covering a wide range in composition and concentration (Chapter 10) and predicting interactions between sulfate solid solutions and aqueous solutions (Chapter 11). The concluding chapter on stable-isotope systematics (Chapter 12) discusses the utility of sulfate minerals in understanding the geological and geochemical processes in both high-and low-temperature environments, and in unraveling the past evolution of natural systems through paleoclimate studies. We thank the authors for their comprehensive and timely efforts, and for their cooperation with our various requests regarding consistency of format and nomenclature. Special thanks are due to the numerous scientists who provided peer reviews, which substantially improved the content of the chapters. This volume would not have been possible without the usual magic touch and extreme patience of Paul H. Ribbe, Series Editor for Reviews in Mineralogy and Geochemistry. Finally, we thank our families for their support and understanding during the past several months.