Ammoniomathesiusite
Ammoniomathesiusite is an IMA-recognized mineral species in the vanadate class, with the chemical formula (NH₄)₅(UO₂)₄(SO₄)₄(VO₅)·4H₂O.
It crystallizes in the tetragonal crystal system (space group P4/n). It is a member of the Mathesiusite structural group.
Key properties: Mohs hardness 2.5; specific gravity 3.672; Very pale yellow streak; Vitreous luster; optically uniaxial.
IMA symbol Amat, IMA status: approved, named in 2017.
Found in a U-V roll-front deposit in sandstone; a product of postmining oxidation of a montroseite-corvusite assemblage with pyrite and chalcopyrite. The NH4+ presumably derived from organic matter.
It is found associated with Ammoniozippeite, gypsum, jarosite, natrozippeite, asphaltum, quartz.
The prefix indicates the ammonium analogue of K-dominant mathesiusite.