Outstanding orange rounded aggregates of plavnoite crystals from the TL and only known locality worldwide in Plavno (Plavno Mine, Krušné Hory Mountains, Karlovy Vary Region, Czech Republic). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Plavnoite
A rare potassium-manganese uranyl sulfate from the Plavno mine at Jáchymov.
Intro adapted from Wikipedia (CC BY-SA).
Plavnoite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₀.₈Mn₀.₆[(UO₂)₂O₂(SO₄)]·3.5H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Zippeite structural group.
Key properties: Mohs hardness 2; specific gravity 4.926; Pale orange streak; Vitreous to silky luster; optically biaxial.
IMA symbol Pvn, IMA status: approved, named in 2015.
A secondary alteration mineral formed by hydration-oxidation weathering of uraninite in a hydrothermal Ag-Bi-Co-Ni-U vein deposit.
It is found associated with Marécottite, magnesiozippeite, blatonite, gypsum.
The name refers to the mine in which the first samples were collected.