Well formed orange brown grischunite crystals associated to almost white tilasite crystals. Grischunite has only been found in this locality worldwide, so it's a real rarity. From: Falotta, Tinzen, Grischun, Switzerland. — Photo: David Hospital · CC BY-SA 4.0
Grischunite
Grischunite is an IMA-recognized mineral species in the arsenate class, with the chemical formula NaCa₂Mn²⁺₅Fe³⁺(AsO₄)₆·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Pcab). It is a member of the Wicksite structural group.
Key properties: Mohs hardness 5; specific gravity 3.8; Yellow-brown to orange streak; Vitreous luster; optically biaxial.
IMA symbol Gcn, IMA status: approved, named in 1981.
An alteration product of sarkinite in a manganese deposit.
It is found associated with Sarkinite, brandtite, manganoan berzeliite, tilasite, rhodochrosite, braunite.
The name comes from the former Romansch name Grischun for Graubünden Canton.