Brownish crystal aggregates of thevery rare Ca-Mn silicate mineral okhotskite from the TL in Japan (Kokuriki Mine, Kitami City, Okhotsk Subprefecture, Hokkaidō Prefecture, Hokkaido Island, Japan). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Okhotskite
Okhotskite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Mn²⁺Mn³⁺₂(Si₂O₇)(SiO₄)(OH)₂·H₂O.
It crystallizes in the monoclinic crystal system (space group A2/m). It is a member of the Pumpellyite structural group.
Key properties: Mohs hardness 6; specific gravity 3.4; Pale orange streak; Vitreous luster; optically biaxial.
IMA symbol Okh, IMA status: approved, named in 1985.
Found in network veinlets cutting hematite-rich ores.
It is found associated with Hematite, quartz, piemontite, neotocite, bementite, apatite, inesite, rhodochrosite.
The name refers to the Sea of Okhotsk, near the type locality in Japan.