February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.

Unlike earlier books in this series, this review describes the selection of chemical thermodynamic data for species of two elements, neptunium and plutonium. Although this came about more by circumstance than design, it has allowed for a more consistent approach to chemical interpretation than might have occurred in two separate treatments. It has also drawn attention to cases where the available data do not show expected parallels, and where further work may be useful to confirm or refute apparent differences in the behaviour of neptunium and plutonium.

Volume 38 of Reviews in Mineralogy provides detailed reviews of various aspects of the mineralogy and geochemistry of uranium. We have attempted to produce a volume that incorporates most important aspects of uranium in natural systems, while providing some insight into important applications of uranium mineralogy and geochemistry to environmental problems. The result is a blend of perspectives and themes: historical (Chapter 1), crystal structures (Chapter 2), systematic mineralogy and paragenesis (Chapters 3 and 7), the genesis of uranium ore deposits (Chapters 4 and 6), the geochemical behavior of uranium and other actinides in natural fluids (Chapter 5), environmental aspects of uranium such as microbial effects, groundwater contamination and disposal of nuclear waste (Chapters 8, 9 and 10), and various analytical techniques applied to uranium-bearing phases (Chapters 11-14). This volume was written in preparation for a short course by the same title, sponsored by the Mineralogical Society of America, October 22 and 23, 1999 in Golden, Colorado, prior to MSA's joint annual meeting with the Geological Society of America.