Asterism - when certain en cabochon cut stones display stars across their surface. These gemstones contain tiny needle-like inclusions of a mineral called rutile, these fibres of rutile intersect each other at various angles to produce the star asterism. Ruby, sapphires, citrine show 6 pointed stars, moonstone and garnet 4 pointed stars. Maker Mends can supply star gemstones. One of the largest star sapphire in the world is the 563.35-carat Star of India.