Star sapphire

Star Sapphire is a very rare form of sapphire that exhibits asterism, a reflective optical effect that highlights a white six-pointed star on the surface of cabochon-cut stones. Star sapphires are more opaque than regular gem-quality sapphires. They were often used in making and decorating devices and objects to ward off hostile magic. A typical specimen had a base value of 1000 gp or 5000 gp depending on market conditions.