In the "Earth’s Treasures" gallery on the second floor of the Royal Ontario Museum, in the back room, on the right hand side of the door, there is a star sapphire called the Star of Lanka, produced in Sri Lanka.
This gem is not spherical in the traditional sense. It must be cut into a cabochon so that the shining star can be seen from the top. The gem weighs 193 carats and was acquired by the museum in 1958.
Starlight is formed by the microscopic inclusions in the gemstone. Because the inclusions are natural hexagonal crystal arrangements, star-shaped sapphires always have six rays of light.