Taaffeite

Chemistry: Beryllium magnesium aluminate.
Crystal system: Hexagonal; trapezohedral.
Color: Transparent; red, pink, blue, mauve, green.
Hardness: 8
Cleavage: -
Specific gravity: 3.613
Refractive index: 1.718 – 1.723; Uniaxial negative; 0.004
Luster: Vitreous
Dispersion: -
Dichroism: -
Occurrence: Sri Lanka, China, Tanzania.

Notes
First discovered in 1945 by Count Taaffe; rare collector’s stone; appearance and values close to spinel but distinguished by birefringence; fluorescence: green in UV; faceted.