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November-December 2015

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Who's Who in Mineral Names: Jeffrey Edward Post (b. 1954)

Postite, Mg(H2O)6Al2(OH)2(H2O)8(V10O28)•13H2O, is an orthorhombic hydrous decavanadate stabilized by an interstitial unit consisting of hydrated magnesium and aluminum hydroxide. It was named in honor of Dr. Jeffrey E. Post, curator-in-charge of the National Gem and Mineral Collection, U.S. National Museum of Natural History (Smithsonian Institution). It was discovered and described from cotype localities in the La Sal mining district, Utah: the Vanadium Queen mine, La Sal Creek Canyon, and the Blue Cap mine, Lyon Canyon Creek, San Juan County, Utah. Crystals of postite are thin, golden-yellow, elongated prisms terminated by pyramids. They occur as needles on corvusite-montrosite-bearing sandstone blocks. Although first discovered at the Vanadium Queen mine, better crystals were later found at the Blue Cap mine in the same stratigraphic horizon some distance to the east. Associated minerals include baryte, calcite, clausthalite, devilline, dickthomssenite, hewettite, lasalite, magnesiopascoite, martyite, natrozippeite, navajoite, paramontroseite, pascoite, pyrite, rossite, selenium, sherwoodite, sulfur, tyuyamunite, uranophilite, and zeunerite. Postite forms from the oxidation of corvusite-montrosite assemblages in a moist environment, where aqueous solutions acidified by the breakdown of pyrite mobilize and precipitate secondary vanadate phases at near-surface conditions. It is a rare species (Kampf et al. 2012).

Jeffrey Edward Post was born in Madison, Wisconsin, in 1954. From an early age, he collected minerals, rocks, and fossils. Growing up, he always enjoyed both geology and chemistry and was fortunate to find a career that combined these interests.

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