The star sapphire is that variety of sapphire in which, when the stone is cut and rounded off horizontal with the dome of the crystal, the light is condensed across the three lines of crystalline interference. Three cross lines produce a star which moves as a source of light, or as it is moved from the source of light. Star sapphires very rarely possess the deep blue color of the fine blue sapphire; generally the color is somewhat impure, or of a milky-blue, or else a blue-gray, or sometimes almost a pure white. The blue-gray, gray, and white stones frequently show a much more distinct star, possibly from the fact that there are more inclusions between the layers of the crystals than with the darker blue stones, as it is the set of interference bands that produces the peculiar light.
The great Oriental traveller, Sir Richard Francis Burton, had a large star sapphire or asteria, as it was called. He referred to it as his talisman, for it always brought him good horses and prompt attention wherever he went; in fact, it was only in those places where he received proper attention that he would show it to the natives, a favor they greatly appreciated because the sight of the stone was believed to bring good luck. The fame of Burton’s asteria travelled ahead of him, and it served him well as a guiding-star. De Boot, writing in the seventeenth century, states that such a stone was called Siegstein (victory-stone) among the Germans.
The remarkable asteria, known as the “Star of India,” in the Morgan-Tiffany Collection in the American Museum of Natural History, has a more or less indefinite historic record of some three centuries, but after its many wanderings it has now found a worthy resting-place in the great Museum. Its weight is 543 carats. (The subject of the origin, development and reform of the caratweight has been fully treated by the author in the Trans. of the Soc. of Min. Engineers, 1913, pp. 1225-1245, “The New International Metric Diamond Carat of 200 milligrams.”)
The asteria, or star sapphire, might be called a “Stone of Destiny,” as the three cross-bars which traverse it are believed to represent Faith, Hope, and Destiny. As the stone is moved, or the light changes, a living star appears. As a guiding gem, warding off ill omen and the Evil Eye, the star-sapphire is worn for the same reasons as were the oculus mundi and the oculus Beli. One of the most unique of talismanic stones, it is said to be so potent that it continues to exercise its good influence over the first wearer even when it has passed into other hands.