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2. 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]

3. Star sapphire - Wikipedia

   en.wikipedia.org/wiki/Star_sapphire

   Star sapphire, a type of sapphire gemstone that exhibits a star-like reflection of light (an asterism) The Armstrong Siddeley Star Sapphire, a British car manufactured from 1958 to 1960; Star Sapphire (DC Comics character), the name of several fictional supervillains in DC Comics publications; Star Sapphire, a fictional character from the ...

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. List of sapphires by size - Wikipedia

   en.wikipedia.org/wiki/List_of_sapphires_by_size

   Sapphire Origin Date Size Cut Color Location Ref Star of Adam: Sri Lanka 2015 1,404.49 carats (280.898 g) 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]

6. 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 ...

7. Verneuil method - Wikipedia

   en.wikipedia.org/wiki/Verneuil_method

   However, the Verneuil process could also be used for the production of other stones, including blue sapphire, which required oxides of iron and titanium to be used in place of chromium oxide, as well as more elaborate ones, such as star sapphires, where titania (titanium dioxide) was added and the boule was kept in the heat longer, allowing ...