Sapphirine

Chemistry: Silicate containing magnesium and aluminum.
Crystal system: Monoclinic; small tabular pseudo-hexagonal.
Color: Transparent; dark blue to intense blue, blue, brownish green, purplish pink.
Hardness: 7.5
Cleavage: Indistinct: 3 directions.
Specific gravity: 3.51 (3.4 – 3.58)
Refractive index: 1.705 – 1.718; biaxial positive; 0.006-0.007
Luster: Vitreous.
Dispersion: -
Dichroism: Strong.
Occurrence: In metamorphic rocks; gem quality: Sri Lanka, Thailand, Australia, Madagascar.

Notes
Rare metamorphic mineral; named after its sapphire blue color; faceted.