Star of Bombay corundum sapphire - Smithsonian Museum of Natural History - 2012-05-17
The Star of Bombay, a cabochon-cut star sapphire, on display in the Hall of Gems and Minerals at the Smithsonian Museum of Natural History in Washington, D.C.
Sapphires are gemstones that are made of the mineral corundum (crystalline aluminum oxide). Pure corundum is colorless, but when trace elements like chromium, vanadium, iron, or nickel get mixed in it takes on color. The red variety is known as ruby; all the other varities are known as sapphires. The violet-blue color is caused by the presence of titanium, iron, and vanadium.
The star effect is known as asterism. Minute fibers of titanium oxide (known as "rutile fibers" or "silk") have formed inside the mineral. These fibers can only form at 60-degree angles to one another. This causes the "star" effect. A gemologist has to carefully analyze the mineral before polishing it to choose exactly the right angle. Only at the right angle does the star effect become most apparent.
The “Star of Bombay” is 182 carats. (A carat is 200 milligrams). It is cabochon-cut, which means it is shaped and polied rather than faceted. It is also dome-shaped.
The jewel came from Sri Lanka, not India. It was acquired by the jewelry firm of Trabert & Hoeffer (New York), although it is unclear if it was already cut and polished by then or if it already had its name by then. Where it came from in Sri Lanka is completely unknown.
The gem was set in a necklace of diamonds and sapphires in a platinum setting, and given by Douglas Fairbanks, Sr. to Mary Pickford as a wedding gift. She bequeathed it to the Smithsonian Institution. At her death in 1979, the Smithsonian actually traded a $15,000 diamond necklace, $45,000 sapphire bracelet, and $34,000 sapphire ring for it.
It went on display in 1984.
Lots of people erroneously report that this was in a ring setting; sorry! no! They also confuse it with the "Star of Bombay" diamond, which is in a ring setting.
Star of Bombay corundum sapphire - Smithsonian Museum of Natural History - 2012-05-17
The Star of Bombay, a cabochon-cut star sapphire, on display in the Hall of Gems and Minerals at the Smithsonian Museum of Natural History in Washington, D.C.
Sapphires are gemstones that are made of the mineral corundum (crystalline aluminum oxide). Pure corundum is colorless, but when trace elements like chromium, vanadium, iron, or nickel get mixed in it takes on color. The red variety is known as ruby; all the other varities are known as sapphires. The violet-blue color is caused by the presence of titanium, iron, and vanadium.
The star effect is known as asterism. Minute fibers of titanium oxide (known as "rutile fibers" or "silk") have formed inside the mineral. These fibers can only form at 60-degree angles to one another. This causes the "star" effect. A gemologist has to carefully analyze the mineral before polishing it to choose exactly the right angle. Only at the right angle does the star effect become most apparent.
The “Star of Bombay” is 182 carats. (A carat is 200 milligrams). It is cabochon-cut, which means it is shaped and polied rather than faceted. It is also dome-shaped.
The jewel came from Sri Lanka, not India. It was acquired by the jewelry firm of Trabert & Hoeffer (New York), although it is unclear if it was already cut and polished by then or if it already had its name by then. Where it came from in Sri Lanka is completely unknown.
The gem was set in a necklace of diamonds and sapphires in a platinum setting, and given by Douglas Fairbanks, Sr. to Mary Pickford as a wedding gift. She bequeathed it to the Smithsonian Institution. At her death in 1979, the Smithsonian actually traded a $15,000 diamond necklace, $45,000 sapphire bracelet, and $34,000 sapphire ring for it.
It went on display in 1984.
Lots of people erroneously report that this was in a ring setting; sorry! no! They also confuse it with the "Star of Bombay" diamond, which is in a ring setting.