Star sapphire – a sapphire with a star on the surface

Star sapphire – a star hidden in a gemstone
Asterisk sapphire is a special type of sapphire (Al₂O₃) that, when cut into a cabochon, exhibits an optical effect called asterism. When light hits the surface of the stone, a star appears, usually with six rays, rarely with twelve. This effect is caused by inclusions of rutile in the crystal.

Location and origin of asterisk sapphires
The most famous asterisk sapphires come from Sri Lanka, Burma (Myanmar) and Thailand. Sri Lanka (Ceylon) is still considered one of the best locations for star sapphires with an intense blue color and pronounced asterism.

History and uses of star sapphires
Asterisk sapphires have fascinated mankind for centuries. In Asia, they were considered rare gems symbolizing fate and luck. It is still a sought-after collector's gem and its value depends on the color, size and sharpness of the star.

Identification of aster sapphire

Chemical formula: Al₂O₃

Color: most often blue, rarely pink, black or yellow

Crystal appearance: prismatic, hexagonal

Crystal system: hexagonal

Hardness: 9 (Mohs scale)

Luster: vitreous to silky (cabochon)

Cleavage: none

Scratch: white

Density: 3.9 – 4.1 g/cm³