Okayamalite
Okayamalite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂B₂SiO₇.
It crystallizes in the tetragonal crystal system (space group P-42_1m). It is a member of the Melilite structural group.
Key properties: Mohs hardness 5.5; specific gravity 3.3; White streak; Earthy luster; optically uniaxial.
IMA symbol Oky, IMA status: approved, named in 1997.
Found in skarn by boron metasomatism of a wollastonite-calcite aggregate (Japan); probably by desilication-dehydroxylation of datolite in a magnetite-hematite skarn deposit (Norway).
It is found associated with Wollastonite, vesuvianite, calcite, johnbaumite (Japan); datolite, calcite, apophyllite, chlorite, amorphous silica (Norway).
The name refers to Okayama prefecture, Japan.