Sounds like a condition, and in the world of gems, it is. When needle-like inclusions (often minerals composed of titanium dioxide) intersect following the underlying structure of the crystal, it creates a six-rayed pattern on this type of Sapphire, exhibiting a star-like phenomenon which is called - yes - Asterism. These crystals are cut in cabochon as seen in picture, with the star on the top of the dome.
The Black Star of Queensland is believed to be the largest star sapphire ever mined weighing 733 carats, discovered in the 1930s in the Anakie Sapphire fields of the Rubyvale area in the State of Queensland, in northeastern Australia. Followed by the Star of India weighing 563.4 carats. The latter is currently in display at the American Museum of Natural History, in NY city.
The visibility and intensity of the Asterism (the star-like pattern) along with the weight will determine the value of the Star Sapphire. The Black Star of Queensland would make its way around the world, weaving in and out of spotlight and obscurity, with stops in the Smithsonian in the '60s, on Cher's neck in the '70s, and at the Royal Ontario Museum in Toronto in 2007. Currently, the sapphire is owned by an unknown private party and is not believed to be on public display.
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