Star sapphire is a very rare variety of sapphire known for its unique optical phenomenon called asterism.
This incredible "star effect" appears as a 6-point star moving across the gem's surface as it interacts with direct light. Star sapphires occur naturally in various colors including blue, pink, purple, yellow, orange, green, gray, and black. (The red variety would be considered a star ruby.)
Star sapphire is presently found in Sri Lanka (Ceylon), Burma (Myanmar), Thailand, and Australia, as well as other locations worldwide to a lesser extent.