Iyoite
A very rare manganese-copper chloride-hydroxide — an atacamite-group mineral with ordered Mn and Cu.
Intro adapted from Wikipedia (CC BY-SA).
Iyoite is an IMA-recognized mineral species in the halide class, with the chemical formula MnCuCl(OH)₃.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Atacamite structural group.
Key properties: Mohs hardness 3.22; specific gravity 3.22; Vitreous luster; optically biaxial.
IMA symbol Iy, IMA status: approved, named in 2013.
A secondary mineral formed by reaction between seawater and primary ore minerals (hausmannite, tephroite, alleghanyite, rhodonite, rhodochrosite, copper, chalcocite) in greenschist facies, metamorphosed.
It is found associated with Cuprite, kutnohorite, malachite, chrysocolla, misakiite.
The name refers to the Sea of Iyo, located near the Sadamisaki Peninsula, Japan.