Star sapphire is rare variety of sapphire that exhibits a rare asterism under specific lighting. When viewing star sapphire, a six-rayed star will appear to float across the surface of the stone. The effect is best viewed under a direct light source and while tilting and rotating the stone from different angles. Star sapphires contain unusual tiny needle-like inclusions of rutile. Aligned needles that intersect each other at varying angles produce the rare phenomenon known as asterism.