Star sapphire

star sapphire

A star sapphire is a type of corundum sapphire that exhibits a star-like phenomena known as asterism.

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Red corundum are rubies. The stone contain intersecting needle-like inclusions. It follows the underlying crystal structure. That causes the appearance of a six-rayed star-shaped pattern. When viewed with a single overhead light source. The inclusion is often silk needles. The stones are cut as cabochon. It is better if the center of the star is on the top of the dome.

Twelve-rays star sapphire stone

Occasionally, twelve-rayed stars can be visible. Typically because two different corundum crystal grow together in the same structure. Such as a combination of fine needles with small platelets of hematite. The first results in a whitish star. And the second results in a golden-colored star.

During crystallisation, the two types of inclusions become preferentially oriented in different directions within the crystal. Thereby forming two six-rayed stars.

They are superimposed upon each other to form a twelve-rayed star. Misshapen stars or 12-rayed stars may also form as a result of twinning. The inclusions can alternatively produce a cat’s eye effect.

If the face-up direction of the cabochon’s dome is oriented perpendicular to the crystal’s c-axis. Rather than parallel to it. If the dome is oriented in between these two directions. An off-center star will be visible. Offset away from the high point of the dome.

World records

The Star of Adam is the largest gemstone which weighs 1404.49 carats. We found the gem in the city of Ratnapura, southern Sri Lanka. Also, The Black Star of Queensland, the second largest gem-quality in the world, weighs 733 carats.

Star of india sapphire gem

Another, The Star of India comes from in Sri Lanka. Its weight is 563.4 carats. It is the third-largest star sapphire. And is currently on display at the American Museum of Natural History in New York City. Furthermore, the 182 carat Star of Bombay, mined in Sri Lanka and located in the National Museum of Natural History in Washington, D.C.

It is another example of a large blue star sapphire. The value of a gemstone depends not only on the weight of the stone, but also the body color, visibility, and intensity of the asterism.

Star sapphires untreated from Myanmar (Burma)

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