A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism. Star sapphires contain intersecting needle-like inclusions (often the mineral rutile, a mineral composed primarily of titanium dioxide that cause the appearance of a six-rayed 'star'-shaped pattern when viewed with a single overhead light source. The value of a star sapphire depends not only on the carat weight of the stone but also the body color, visibility and intensity of the asterism.
The Star of India is thought to be the largest star sapphire in the world and is currently on display at the American Museum of Natural History in New York City. The 182 carat (36.4 g) Star of Bombay, housed in the National Museum of Natural History, Washington D.C., is a good example of a blue star sapphire.
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