Postite
Postite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Mg(H₂O)₆Al₂(OH)₂(H₂O)₈(V₁₀O₂₈)·13H₂O.
It crystallizes in the orthorhombic crystal system (space group Pccn). It is a member of the Pascoite structural group.
Key properties: Mohs hardness 2; specific gravity 2.226; Yellow streak; Subadamantine luster; optically biaxial.
IMA symbol Pos, IMA status: approved, named in 2011.
From the oxidation of montroseite-corvusite assemblages in a moist environment in Colorado-type sandstone-hosted uranium deposits.
It is found associated with Corvusite, montroseite.
The mineral was named to honor Jeffrey E. Post (b. 1954), Curator-in-Charge of the National Gem and Mineral Collection, U.S. National Museum of Natural History (Smithsonian Institution).