Gunterite
Gunterite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Na₄Ca[V₁₀O₂₈]·20H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Pascoite structural group.
Key properties: Mohs hardness 1; specific gravity 2.398; Yellow streak; Subadamantine luster; optically biaxial.
IMA symbol Gun, IMA status: approved, named in 2011.
Found in efflorescencent crusts on mine walls and in fractures in sandstone, formed by the oxidation of montroseite–corvusite assemblages.
It is found associated with Montroseite, corvusite, huemulite, rossite, calcite, hewettite, hughesite, munirite, paramontroseite, pascoite, sherwoodite, rakovanite.
The mineral was named to honor Professor Mickey Eugene Gunter (b. 1953), University of Idaho, Moscow, Idaho, USA, for his studies in optical mineralogy and the mineralogy of asbestos minerals.