Itoigawaite exhiibited at the Mining Museum of Akita University — Photo: 掬茶 · CC BY-SA 4.0
Itoigawaite
Itoigawaite is an IMA-recognized mineral species in the silicate class, with the chemical formula SrAl₂Si₂O₇(OH)₂·H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Lawsonite structural group.
Key properties: Mohs hardness 5–5.5; specific gravity 3.37; White streak; Vitreous luster; optically biaxial.
IMA symbol Ito, IMA status: approved, named in 1998.
Product of late-stage high-P/T metamorphism, in a thin veinlet cutting a lavender- colored Ti-bearing jadeitite boulder in a river cutting serpentinite melange.
It is found associated with Jadeite, natrolite, Sr-bearing pectolite, rutile, titanite.
The name refers to the district in Japan, Itoigawa-Ohmi, where the first samples were collected.