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2. Asterism (gemology) - Wikipedia

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

   The archetypal asteria is the star sapphire, generally corundum with near uniform impurities which is bluish-grey and milky or opalescent, which when lit has a star of six rays. In the red instance stellate reflection is rarer; the star-ruby occasionally found with the star-sapphire in Sri Lanka is among the

3. Rutile - Wikipedia

   en.wikipedia.org/wiki/Rutile

   Small rutile needles present in gems are responsible for an optical phenomenon known as asterism. Asteriated gems are known as "star" gems. Star sapphires, star rubies, and other star gems are highly sought after and are generally more valuable than their normal counterparts. Rutile is widely used as a welding electrode covering.

4. 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.

5. Verneuil method - Wikipedia

   en.wikipedia.org/wiki/Verneuil_method

   Depending on the desired colouration of the crystal, small quantities of various oxides are added, such as chromium oxide for a red ruby, or ferric oxide and titania for a blue sapphire. Other starting materials include titania for producing rutile, or titanyl double oxalate for producing strontium titanate. Alternatively, small, valueless ...

6. 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.

7. List of sapphires by size - Wikipedia

   en.wikipedia.org/wiki/List_of_sapphires_by_size

   Star Blue-violet National Museum of Natural History, Washington [9] Star of Bombay: Sri Lanka 182 carats (36.4 g) Star Blue-violet National Museum of Natural History, Washington [10] Ruspoli Sapphire: 136.9 carats (27.38 g) [11] Stuart Sapphire: Sri Lanka 104 carats (20.8 g) Blue Tower of London [12] Bismarck Sapphire: Myanmar: 98.56 carats (19 ...