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March-April 2011

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Connoisseur's Choice: Wavellite, Mauldin Mountain, Montgomery County, Arkansas

Phosphate minerals are a traditional favorite of many mineral collectors. They are colorful and of widespread geologic and geographic occurrence. Clearly, minerals such as pyromorphite, mimetite, other members of the apatite group, and a very long list of additional minerals, all characterized by the phosphate radical, are some of the most attractive species and indeed represent some of our most valuable specimens.

Interestingly, however, many of our favorite phosphates are of only secondary origin, forming during the weathering of metal-bearing deposits or even from the decomposition of other primary phosphates, a common situation in some pegmatite districts. Of course, phosphate is a highly sought economic commodity, both as a fertilizer component and for the production of industrially important phosphoric acid. Its commercial deposits often are nothing more than impure beds of one or more of the apatite species, having formed in an ancient, restricted marine environment whose rocks are now stranded on dry ground, sometimes far from the present coast. In terms of distribution in mineral collections, some interesting issues arise. Some phosphate minerals are quite colorful yet are relatively common and have been sold as specimens for more than a century from occurrences that are still productive today. It is likely that many collectors' first phosphate specimen was a wavellite from one of the traditional Arkansas localities, for these have been available from dealers, beginning with A. E. Foote, seemingly forever. These unusual occurrences have recently been the source of some of the finest wavellite ever found, and, consequently, one such specimen has been selected as this issue's Connoisseur's Choice.

Dr. Robert B. Cook, an executive editor of Rocks & Minerals, is a professor emeritus in the Department of Geology and Geography at Auburn University, Auburn, Alabama. He welcomes suggestions for this column and can be contacted at the addresses above.

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