Chrysoberyl
Description
A hard green to yellow mineral composed of beryllium aluminate. Chrysoberyl occurs in granitic rocks, pegmatites, and mica schists. Some transparent varieties of chrysoberyl have been used as gemstones. In the 18th century, a large deposit of clear, yellowish-green chrysoberyls was found in Brazil and the stones were popularly used for Portuguese and Spanish jewelry. Cat's eye chrysoberyls are cut as cabochons and polished. The Alexandrite variety of chrysoberyl appears red in artificial light and green in daylight. Chrysoberyls are found in the Ural Mountains (alexandrite), Czech Republic, Sri Lanka, Rhodesia, Brazil, Malagasy Republic and the United States (New York, Colorado).
Synonyms and Related Terms
cat's eye; cymophane; golden beryl; alexandrite; oriental chrysolite; crisoberilo (Esp., Port.); chryzoberyl (Pol.); Chrysoberyll (Deut.); chrysoberyl (Ned.)
Physical and Chemical Properties
- Orthorhombic crystal system with tabular or short prismatic crystals
- Good cleavage in one direction
- Fracture = uneven to conchoidal
- Luster = vitreous
- Streak = colorless to white
- Fluorescence = generally inert; yellow to green stone may show weak yellow under SW; 'mint' chrysoberyl shows strong red in LW
- Pleochroism = generally weak to moderate (red, yellow, green); Alexandrite is strongly pleochroic (green, red)
| Composition | BeAl2O4 |
|---|---|
| Mohs Hardness | 8.5 |
| Density | 3.5-3.8 g/ml |
| Refractive Index | 1.745-1.754 |
| Birefringence | 0.008 - 0.010 |
Comparisons
Resources and Citations
- Mineralogy Database: Chrysoberyl
- Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
- Gem Identification Lab Manual, Gemological Institute of America, 2016.
- R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
- Encyclopedia Britannica, http://www.britannica.com Comment: "chrysoberyl." Accessed 7 Apr. 2005 .
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Wikipedia: Chrysoberyl (Accessed Sept. 2, 2005 and Dec 2022)
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 101
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998