Rengeite
Rengeite is an IMA-recognized mineral species in the silicate class, with the chemical formula Sr₄Ti₄ZrO₈(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 5–5.5; specific gravity 4.12; Pale greenish brown streak; Adamantine luster.
IMA symbol Rge, IMA status: approved, named in 1998.
Found in jade pebbles from rocks in a high P/T metamorphic belt as tectonic inclusions in serpentinite melange. Orthorhombic polymorph occurs as domains to 5 μm in monoclinic rengeite.
It is found associated with Jadeite, natrolite, rutile, titanite, pectolite, itoigawaite.
The name refers to Mt. Renge and the Renge metamorphic belt where jadeitite deposits occur in Japan.