This article is about the characteristic in some gems. For other uses, see Asterism

In gemmology, an asterism is an optical phenomenon displayed by some rubies, sapphires, and other gems of an enhanced reflective area in the shape of a “star” on the surface of a cabochon cut from the stone.

A distinction can be made between two types of asterism:

• Epiasterism, such as that seen in sapphire and most other gems, is the result of a reflection of light on parallel arranged inclusions inside the gemstone.
• Diasterism, such as that seen in rose quartz, is the result of light transmitted through the stone. In order to see this effect, the stone must be illuminated from behind.

References

• AIGS (Bangkok) and New Aurora Gem lab (Mogok) present: A new rare File Format: PDF/Adobe Acrobat - View as HTMLA Mogok gemologist familiar with Poudretteite was excited when he discovered this gem. He. had some interest in Scapolite as its’ properties approximate
• Topazius, Peridot King: Gems or Decorative Stones This gem derived its name from the island in the Red Sea, 300 stadia (37-1/2 miles) off the mainland, where it was first discovered ; Juba, quoted by Pliny
• Diamond Education,Diamond Information Later that night, when Nadir Sha h unfolded the host's turban he discovered the gem. Upon seeing it he exclaimed, "Koh-i-noor," meaning "mountain of light.
• Commodore 64 - Night Gem Anyway, I also discovered the fabulous world of emulators. Little gems like CCS64 and WinVICE have brought me many hours of fun until now, and I know that
• GEMS FROM THE COLLECTION OF PRINCESS DASHKOV Princess Dashkov also owned gems discovered by. eighteenth-century archaeologists in various parts of. the world, including the Mediterranean lands and the
• ASIA BEACHES: Gems waiting to be discovered. - Journal, Magazine ASIA BEACHES: Gems waiting to be discovered. Publication Date: 17-DEC-04 Publication Title: Travel Trade Gazette UK & Ireland
• Topazius, Peridot King: Precious Stones and Gems This gem derived its name from the island in the Red Sea, 300 stadia (30 miles) off the mainland, where it was first discovered ; Juba, quoted hy Pliny (32)
• Rare Gem Triplite Specimen Discovered in Tucson News , Press Release and Blog Rare Gem Triplite Specimen Discovered in Tucson. PRNN News , Press Release and Blog Dish Logo
• The Secret Life of Shoes: Jazz Shoe Gems Discovered Jazz Shoe Gems Discovered. Only Shoes In MindBooks, Shoes, Music and Accessories. Thelonious Monk Quartet with John Coltrane- At Carnegie Hall
• Lets'eng Produces Four More Gems In November 2003, the mine discovered a 215 carat diamond, a week later, the company discovered a 95 carat gem on its sorting table.
• The Dynamic Earth @ National Museum of Natural History The gems in the National Gem Collection were discovered in all corners of the world and are among the Earth's great splendors.
• Colored Stone May/June 2003 - Rukwa: Tanzania's Unknown Gem Giant Other gems have also been discovered which have not yet been identified. Many of Rukwa's local people base their technical know-how on witchcraft;
• Scoop: U.S. Election Integrity Flaw Discovered At Diebold SYSTEM INTEGRITY FLAW DISCOVERED AT DIEBOLD ELECTION SYSTEMS . Harris: "…you guys have a file on your FTP that says "Replace the GEMS files with these.
• Shell Controls: Delphi's Hidden Gems Delphi's shell controls are hidden gems: they are hard to find and lack any meaningful documentation. I discovered them, almost by accident, while working