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March-April 2016

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Who's Who in Mineral Names: Alexander U. Falster (b. 1952)

Falsterite, ideally Ca2MgMn22+(Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14, is a late-stage secondary phosphate (Kampf et al. 2012). It was named in honor of Alexander U. Falster in recognition of his research on pegmatites and pegmatite minerals (e.g., columbite-group minerals [Falster, Simmons, and Webber 2001]), tourmaline-group minerals (Simmons et al. 2005), REE minerals (Hanson et al. 2012), and londonite (Simmons et al. 2001). He has described the mineralogy and geochemistry of NYF-type pegmatites of the Wausau complex in Marathon County, Wisconsin (Falster, Buchholz, and Simmons 2013), and the LCT-type pegmatites of Florence County, Wisconsin (Falster, Simmons, and Webber 1996). He has been a coauthor on the descriptions of seven new pegmatite minerals: esperanzaite (Foord et al. 1999a), simmonsite (Foord et al. 1999b), londonite (Simmons et al. 2001), pezzottaite (Laurs et al. 2003), samarskite-(Yb) (Simmons, Hanson, and Falster 2006), galliskiite (Kampf et al. 2010), and nizamoffite (Kampf et al. 2013). Falsterite was discovered in a zinc- and lead-rich phosphate-carbonate assemblage at the margin of a 1.5-meter triphlite crystal in the core margin of the Palermo No. 1 pegmatite, North Groton, Grafton County, New Hampshire. It occurs in small cavities in a 10–30-cm-thick alteration rind consisting mainly of siderite, fluorapatite, and quartz along one side of a large triphylite crystal. This carbonate-rich zone also hosts a number of locally abundant sulfides including pyrite, sphalerite, galena, and chalcopyrite. A considerable fraction of the sulfides has been altered by aqueous phosphate- and carbonate-bearing solutions resulting in the formation of numerous secondary Zn- and Pb-bearing phosphate and carbonate species including phosphophyllite, parascholzite, schoonerite, keckite, smithsonite, pyromorphite, and cerussite (Nizamoff et al. 2007). Falsterite is monoclinic and forms extremely thin, blue-green rectangular plates and laths to 1 mm that exhibit {010}, {100}, and {001} crystal forms. Crystals are transparent and typically flattened on {010}, elongate along [100], and exhibit lamellar twinning. Falsterite has also been identified from the Estes quarry, West Baldwin, Cumberland County, Maine, where it is associated with sphalerite, schoonerite, quartz, fairfieldite, and muscovite.

Dr. Steven C. Chamberlain, a consulting editor of Rocks & Minerals, is an avid collector and researcher specializing in the minerals of New York State.

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