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Asterism (gemmology)
From Wikipedia, the free encyclopedia
- This article is about the characteristic in some gems. For other uses, see Asterism
| This article or section relies largely or entirely upon a single source. Please help improve this article by introducing appropriate citations of additional sources. |
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. Star sapphires and rubies get their asterism from the titanium dioxide impurities (rutile) present in them.[1]
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.
- ^ Emsley, John (2001). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press, pp. 451 – 53. ISBN 0-19-850341-5.
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| Precious metals: | Gold · Silver (Sterling silver) · Platinum · Palladium |
| Gemstones: | Diamonds · Rubies · Emeralds · Sapphires · Amethyst · Opals · Topaz · Aquamarine · Tanzanite · Alexandrite |
| Others: | Amber · Pearls |