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2. Black Star sapphire - Wikipedia

   en.wikipedia.org/wiki/Black_Star_sapphire

   Black star sapphire, also known as 'natural star sapphire' is a type of corundum (aluminum oxide). It is usually cut into a dome shape to show a star feature. If it is cut with a flat or almost flat face, then a golden colour is revealed. The chemical composition and features for black star were analyzed in the Journal of Gemmology. [citation ...

3. Asterism (gemology) - Wikipedia

   en.wikipedia.org/wiki/Asterism_(gemology)

   The star-effect may be also caused by the inclusions of hematite. In black star sapphire hematite needles formed parallel to the faces of the second order prism produce asterism. Some star sapphires from Thailand contain both hematite and rutile needles forming a 12-ray star. [3] Star-stones were formerly regarded with much superstition. [1]

4. Sapphire - Wikipedia

   en.wikipedia.org/wiki/Sapphire

   A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as "star rubies". Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that causes the appearance of a six-rayed "star"-shaped pattern when viewed with a single overhead light source.

5. Black Star of Queensland - Wikipedia

   en.wikipedia.org/wiki/Black_Star_of_Queensland

   The Black Star of Queensland, also known as the Brimstone of Queensland, named after its nature and place of origin, is a 733-carat (146.6 g) black sapphire, and was the world's largest gem quality star sapphire until The Star of Adam was discovered. The Black Star sapphire is an oval-shaped gemstone cut as a cabochon like all other star ...

6. List of sapphires by size - Wikipedia

   en.wikipedia.org/wiki/List_of_sapphires_by_size

   Star Blue Anonymous owner [3] Black Star of Queensland: Australia 1938 733 carats (146.6 g) Star Black Anonymous owner [4] Star of India: Sri Lanka 563.4 carats (112.68 g) Star Blue-gray American Museum of Natural History, New York [5] Queen Marie of Romania: Sri Lanka 478.68 carats (95.736 g) Cushion Blue Anonymous owner [6] Logan Sapphire ...

7. Star of India (gem) - Wikipedia

   en.wikipedia.org/wiki/Star_of_India_(gem)

   Star of India. The Star of India is a 563.35-carat (112.67 g) star sapphire, one of the largest such gems in the world. [1] [a] It is almost flawless and is unusual in that it has stars on both sides of the stone. The greyish-blue gem was mined in Sri Lanka [3] and is housed in the American Museum of Natural History in New York City.