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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 (19.712 g) Table Blue National Museum of Natural History, Washington [13] James J. Hill Sapphire: 22.66 carats (4.532 g) Cornflower National Museum of Natural History, Washington [14]
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.
Synthetic corundum includes ruby (red variation) and sapphire (other color variations), both of which are considered highly desired and valued. [58] Ruby was the first gemstone to be synthesized by Auguste Verneuil with his development of the flame-fusion process in 1902. [ 59 ]
Corundum is a crystalline form of aluminium oxide (Al 2 O 3) typically containing traces of iron, titanium, vanadium, and chromium. [3] [4] It is a rock-forming mineral.It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. [7]
Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al 2 Si O 4 (F, OH) 2.It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow-orange. [7]
In 1847, Ebelmen made white sapphire by fusing alumina in boric acid. In 1877, Edmond Frémy and industrial glass-maker Charles Feil made crystal corundum from which small stones could be cut. In 1887, Fremy and Auguste Verneuil manufactured artificial ruby by fusing BaF 2 and Al 2 O 3 with a little chromium at red heat .