Matsubaraite
Matsubaraite is an IMA-recognized mineral species in the silicate class, with the chemical formula Sr₄Ti₅O₈(Si₂O₇)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Chevkinite structural group.
Key properties: Mohs hardness 5.5; specific gravity 4.13; White streak; Adamantine luster; optically biaxial.
IMA symbol Mbr, IMA status: approved, named in 2000.
From a boulder of Ti-bearing jadeitite, the product of late stage high-P/T metamorphism.
It is found associated with Jadeite, natrolite, lamprophyllite, titanite, zircon, rutile, tausonite, rengeite.
The mineral was named to honor Dr. Satoshi Matsubara, Department of Geology, National Science Museum, Tokyo, Japan, in recognition of his work on strontium-dominant minerals from Japan.