Abstract The crystal structures and chemical compositions of sulfide minerals are summarized briefly before going on to review their redox chemistries, particularly the roles played by bacteria. In the formation of sulfide minerals, two processes need to be considered; one applicable to all sulfide systems is the microbial reduction of sulfate, the other is microbial reduction of metals, especially iron. Sulfate-reducing prokaryotes (SRP) can supply reactive sulfide ions for the formation of sulfide minerals. The SRP, of which there are more than 120 species, are ubiquitous in many anaerobic environments, although marine sediments are the most important. The SRP are able to grow under extreme conditions of pH and temperature. Bacteria can also conserve energy by reducing metals, such as reduction of Fe(III) coupled to the oxidation of organic matter. Biological processes also mediate the dissolution of sulfides under acid mine drainage conditions, and there are a diversity of acidophilic (pH <3) metal sulfide-oxidizing microorganisms. The oxidation reactions of pyrite, galena, arsenopyrite and chalcopyrite are discussed in detail before considering how toxic metals may be bound to the surfaces of sulfides such as pyrite and mackinawite. The applications of sulfide bacterial redox processes in clean technologies, such as bioleaching and biomining, are discussed briefly.

Abstract Minerals, as the inorganic solids that comprise the rocks, sediments and soils of the Earth, are an essential part of our environment. So, in a sense, all mineralogy is ‘environmental mineralogy’. However, the term ‘environmental’ has come to be employed (particularly in combination with terms such as ‘science’, ‘issue’ or ‘problem’) to refer to those systems at or near the surface of the Earth where the geosphere comes into contact with the hydrosphere, atmosphere and biosphere. This is, of course, the ‘environment’ upon which the human race depends for survival and, hence, is now sometimes referred to as the ‘critical zone’. It can be subject to disruptions due to human activity, particularly activity associated with the exploitation and utilization of Earth’s resources. This is the sense in which we use the term ‘environmental’ in this book. Thus, we consider here those systems containing minerals that constitute the most important or key environments: soils, modern sediments, atmospheric aerosols, and the interior or exterior parts of certain micro- and macro-organisms. Particularly important are the roles that minerals play in processes that act over time to control or influence the environment at various scales of observation. Both pure systems and those contaminated as a result of human activity are considered. We also focus on certain specific problems that arise from resource exploitation or utilization and that involve minerals in some way; either, or both, in creating the problem or ameliorating it. These include problems associated with the waste generated by mining, particularly mining of metals, industrial and domestic wastes, and those wastes produced by the nuclear industry. Particular problems can arise from use of minerals and rocks in buildings and monuments and other cultural artefacts. The relationship between minerals and human health constitutes a special case where the environment includes the human body itself.

Abstract The analytical, experimental and computational methods now used in environmental mineralogy are introduced and illustrated with selected examples. Following a note on the importance of the radiation sources used for diffraction and spectroscopic studies, and a brief reminder of the key role still played by routine methods of mineral characterization (optical microscopy, X-ray powder diffraction [XRD], electron microbeam methods), more specialist techniques for the characterization of bulk solids (including nanoparticles) are considered. These include synchrotron-based advanced XRD and X-ray scattering methods, X-ray absorption spectroscopies, X-ray microprobe techniques, and infrared and Raman spectroscopies. Also considered are transmission electron microscopy, nuclear and magnetic spectroscopies, and particle induced X-ray emission. Following this, attention is focused on the characterization of mineral surfaces and interfaces using low-energy electron diffraction, X-ray reflectivity, X-ray absorption and X-ray standing wave methods, X-ray photoelectron and Auger electron spectroscopies, secondary ion mass spectrometry, environmental scanning electron microscopy, scanning tunnelling and atomic force microscopies and laser confocal microscopy. Computer modelling of solids, surfaces and solution species is discussed briefly before experimental approaches to determining reaction kinetics are considered, followed by experimental studies of the phenomena of adsorption, of evolution of the mineral surface during processes such as silicate weathering, and of how combinations of methods can be used to study the geochemical cycling of arsenic, olivine breakdown, or the comparative reactivities of silicate, carbonate, sulfide and oxide minerals. Environmental mineralogy necessarily begins with the characterization of minerals and associated phases in the key environmental systems. Such characterization involves the identification of minerals, and determination of quantities of the phases, together with compositional and textural information. It may extend to more detailed studies of, for example, very small (‘nano-’) particles, microtextures, or mineral surface chemistry. Beyond such studies of the natural materials, whether ‘pristine’ or ‘contaminated’ through some human activity, it is possible to undertake experiments in the laboratory using minerals or synthetic analogues in order to elucidate some processes of environmental importance. In many low-temperature systems, the minerals occur as both important reactants and as reaction products.