Crystals of ianthinite from Menzenschwand, Germany, partly oxidised to schoepite as well as yellow schoepite crystals pseudomorph after ianthinite — Photo: Klaproth · CC BY-SA 3.0
Ianthinite
Ianthinite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula U⁴⁺₂(UO₂)₄O₆(OH)₄·9H₂O.
It crystallizes in the orthorhombic crystal system (space group P2_1cn).
Key properties: Mohs hardness 2–3; specific gravity 5.16; Dull violet-brown streak; Vitreous to submetallic luster; optically biaxial.
IMA symbol Ian, grandfathered status — known before the IMA’s founding, named in 1926.
A rare secondary mineral found in the unoxidized portions of uranium deposits.
It is found associated with Uraninite, schoepite, becquerelite, kasolite, parsonsite, dewindtite, fourmarierite.
Its name comes from the Greek for violet, in allusion to its color when fresh.