Surinamite
Surinamite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mg₃Al₃O(Si₃BeAlO₁₅).
It crystallizes in the monoclinic crystal system (space group P2/n). It is a member of the Sapphirine structural group.
Key properties: specific gravity 3.3; optically biaxial.
IMA symbol Sum, IMA status: approved, named in 1974.
Found in mylonitic mesoperthite gneiss, probably developed during high-pressure granulite facies metamorphism of aluminous rocks (Bakhuis Mountains, Surinam); in sillimanite-rich segregations in pegmatites (Casey Bay, Antarctica).
It is found associated with Biotite, kyanite, sillimanite, spinel (Bakhuis Mountains, Surinam); quartz, sillimanite, sapphirine, taaffeite (Casey Bay, Antarctica).
The name refers to Surinam, the country of first occurrence.