ALBERT

Description / Table of Contents: At the time of the first printing (1996), interest in the element boron was growing rapidly. We felt that it was an opportune moment to ask investigators active in research on boron to review developments in their respective fields so that readers could learn what was-and wasn't-known about boron and its minerals, geochemistry and petrology. Since 1996, interest in boron has, if anything, increased, and continued demand for the Reviews in Mineralogy "boron bible" has motivated the Mineralogical Society of America to reprint the volume. Demand is reflected in citations, and according to ISI's Science Citation Index, the number of citations since publication to the volume is about 380, with some individual chapters having been cited as many as 44 times. In preparation for this printing, authors of 15 of the 19 original chapters have updated, corrected or added to their chapters within the constraints that no pages be added. Most addenda are bibliographies of literature published since 1996; a few also include summaries of significant findings. Addenda for each chapter follow the chapter, except for those for Chapters 1 and 2, which are merged onto pages 115-116 and 385. A table of new B-minerals since 1996 is given on p. 28, and many modifications were made to the table (p. 7-27) of B-minerals known prior to 1996 (corrections to formulae, mineral names, localities, etc.). Similar up-datings of Table 1 (p. 223) in Chapter 5 and numerous tables in Chapter 9 (p. 387) were undertaken, and Figure 15 in Chapter 11 (p. 619), which-embarrassingly-was missing from the first printing, has been supplied. Addenda to Chapter 13 are introduced on p. 744 and completed on p. 863 and 864. The following salient developments in research related to B are mentioned in the addenda: New minerals. Twenty-two boron minerals have been or are about to be described, and four more have been approved by the International Mineralogical Association, representing an increase of 10%, comparable to the increase in the number of all new minerals described during the same period (Anovitz and Grew, Chapter 1) Tourmaline group. In addition to four new tourmaline species, a new classification has been proposed. Another tourmaline, olenite, has been shown to contain substantial amounts of excess B in tetrahedral coordination, a finding that has revolutionized our view of tourmaline crystal chemistry (Werding and Schreyer, Chapter 3; references in addendum to Henry and Dutrow, Chapter 10). Boron isotopes. New techniques for measuring isotope ratios using secondary ion mass spectroscopy (SIMS) with the ion microprobe open up new opportunities for in situ analyses of individual grains and fluid inclusions (Hervig, Chapter 16). Boron isotopes have found applications in paleoceanography and thus add to the tools available for the study of past climates (Palmer and Swihart, Chapter 13). One of the major questions facing the use of hydrogeochemical models is whether or not they can be used with confidence to predict future evolution of groundwater systems. There is much controversy concerning the validity and uncertainties of non-reactive fluid flow systems. Adding chemical interaction to these flow models only confounds the problem. Although such models may accurately integrate the governing physical and chemical equations, many uncertainties are inherent in characterizing the natural system itself. These systems are inherently heterogeneous on a variety of scales rendering it impossible to know precisely the many details of the flow system and chemical composition of the host rock. Other properties of natural systems such as permeability and mineral surface area, to name just two, may never be known with any great precision, and in fact may be unknowable. Because of these uncertainties, it remains an open question as to what extent numerical models of groundwater flow and reactive transport wilI be useful in making accurate quantitative predictions. Nevertheless, reactive transport models should be able to predict the outcome for the particular representation of the porous medium used in the model. Finally, it should be mentioned that numerical models are often our only recourse to analyze such environmental problems as safe disposal of nuclear waste where predictions must be carried out over geologic time spans. Without such models it would be impossible to analyze such systems, because they involve times too long to perform laboratory experiments. The results of model calculations may affect important political decisions that must be made. Therefore, it is all the more important that models be applied and tested in diverse environments so that confidence and understanding of the limitations and strengths of model predictions are understood before irreversible decisions are made that could adversely affect generations to come.

Description / Table of Contents: The pore scale is readily recognizable to geochemists, and yet in the past it has not received a great deal of attention as a distinct scale or environment that is associated with its own set of questions and challenges. Is the pore scale merely an environment in which smaller scale (molecular) processes aggregate, or are there emergent phenomena unique to this scale? Is it simply a finer-grained version of the “continuum” scale that is addressed in larger-scale models and interpretations? We would argue that the scale is important because it accounts for the pore architecture within which such diverse processes as multi-mineral reaction networks, microbial community interaction, and transport play out, giving rise to new geochemical behavior that might not be understood or predicted by considering smaller or larger scales alone. Fortunately, the last few years have seen a marked increase in the interest in pore-scale geochemical and mineralogical topics, making a Reviews in Mineralogy and Geochemistry volume on the subject timely. The volume had its origins in a special theme session at the 2015 Goldschmidt Conference, Prague, Czech Republic, August 16-21, 2015, where at least some of the contributors to this volume gave presentations. From the diversity of pore-scale topics in the session that spanned the range from multi-scale characterization to modeling, it became clear that the time was right for a volume that would summarize the state of the science. Based in part on the evidence in the chapters included here, we would argue that the convergence of state of the art microscopic characterization and high performance pore scale reactive transport modeling has made it possible to address a number of long-standing questions and enigmas in the Earth and Environmental Sciences. Among these is the so-called “laboratory-field discrepancy” in geochemical reaction rates, which may be traceable in part to the failure to consider porescale geochemical issues that include chemical and physical heterogeneity, suppression of precipitation in nanopores, and transport limitations to and from reactive mineral surfaces. This RiMG volume includes contributions that review experimental, characterization, and modeling advances in our understanding of pore-scale geochemical processes. The volume begins with chapters authored or co-authored by two of the éminences grises in the field of pore-scale geochemistry and mineralogy, two who have made what is perhaps the strongest case that the pore-scale is distinct and requires special consideration in geochemistry. The chapter by Andrew Putnis gives a high level overview of how the pore-scale architecture of natural porous media impacts geochemical processes, and how porosity evolves as a result of these. The chapter makes the first mention of what is an important theme in this volume, namely the modification of thermodynamics and kinetics in small pores. In a chapter authored by Røyne and Jamtveit, the authors investigate the effects of mineral precipitation on porosity and permeability modification of rock. Their principal focus is on the case where porosity reduction results in fracturing of the rock, in the absence of which the reactions will be suppressed due to the lack of pore space. The next chapter by Emmanuel, Anovitz, and Day-Stirrat addresses chemo-mechanical processes and how they affect porosity evolution in geological media. The next chapter by Anovitz and Cole provides a comprehensive review of the approaches for characterizing and analyzing porosity in porous media. Small angle neutron scattering (SANS) plays prominently as a technique in this chapter. Stack presents a review of what is known about mineral precipitation in pores and how this may differ from precipitation in bulk solution. Liu, Liu, Kerisit, and Zachara focus on porescale process coupling and the determination of effective (or upscaled) surface reaction rates in heterogeneous subsurface materials. Micro-continuum modeling approaches are investigated by Steefel, Beckingham, and Landrot, where the case is made that these may provide a useful tool where the computationally more expensive pore and pore network models are not feasible. The next chapter by Noiriel pursues the focus on characterization techniques with a review of X-ray microtomography (especially synchrotron-based) and how it can be used to investigate dynamic geochemical and physical processes in porous media. Tournassat and Steefel focus on a special class of micro-continuum models that include an explicit treatment of electrostatic effects, which are particularly important in the case of clays or clay-rich rock. Navarre-Sitchler, Brantley, and Rother present an overview of our current understanding of how porosity increases as a result of chemical weathering in silicate rocks, bringing to bear a range of characterization and modeling approaches that build toward a more quantitative description of the process. In the next chapter, Druhan, Brown, and Huber demonstrate how isotopic gradients across fluid–mineral boundaries can develop and how they provide insight into pore-scale processes. Yoon, Kang, and Valocchi provide a comprehensive review of lattice Boltzmann modeling techniques for pore-scale processes. Mehmani and Balhoff summarize mesoscale and hybrid models for flow and transport at the pore scale, including a discussion of the important class of models referred to as “pore network” that typically can operate at a larger scale than is possible with the true pore-scale models. Molins addresses the problem of how to represent interfaces (solid–fluid) at the pore scale using direct numerical simulation.