ACKNOWLEDGMENTS
I thank Marie Huizing for affording me the opportunity to write this article, John S. White and Malcolm Southwood for their reviews, and Jeff Scovil, Michael Bainbridge, Christopher Stefano, and Greg Polley for providing the images.
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Notes on contributors
Paul W. Pohwat
Paul W. Pohwat, a consulting editor of Rocks & Minerals, is the manager of the mineral collection of the National Museum of Natural History (Smithsonian Institution).