Chemical Composition : BeAl2O4 Beryllium Aluminum Oxide
Hardness : 8.5
Specific Gravity (Density) : 3.75 (g/cm3)
Refractive Index : 1.746 – 1.756 Biaxial ( + )
Chrysoberyl is a beautiful gem and well suited for jewelry use. The combination of high hardness (8.5) and indistinct cleavage make it very durable. Although its dispersion is low, it is a very bright and colorful gem. Cat’s eye Chrysoberyl is also available. Other gems such as diopside and apatite may be called cat’s eyes, but Chrysoberyl was the original cat’s eye gem. It is the finest cat’s eye of gems. The silky fibers are so fine that a microscope is needed to see the individual fibers. This creates a very sharp cat’s eye effect.
Chrysoberyl is not very well known in the gem world. It is somewhat overshadowed by one of its more famous varieties, Alexandrite. Alexandrite is the best known and most valuable variety of Chrysoberyl. The quality of Alexandrite’s color change effect is what accounts for its desirability and value. It can change from shades of green or blue-green in daylight to shades of mauve, violet, purple or even red in incandescent light. Alexandrite is also available as a cat’s eye gem.
Occurances of Chrysoberyl are widespread, however fine crystals are uncommon. Notable localities include: from many places in Brazil, with exceptional crystals from Tancredo, Itagua¸cu, and Colatina, Espirito Santo; from Faria Lemos, Santa Luzia de Carangola, and Americana, Teófilo Otoni, Minas Gerais; at Campo Formoso, Teixeira de Freitas, and Cachoeira, Bahia. From Maršíkov, Šumperk, Moravia, Czech Republic. At the Izumrudnye mines, Tokovaya River, near Yekaterinburg (Sverdlovsk), and Mursinka, Ural Mountains, Russia. From Miakanjovato, near Lake Alaotra, northeast of Ambatosoratra, Madagascar. Near Masvingo (Ft. Victoria), Zimbabwe. Abundant in gem gravel placers in the Ratnapura district, Sri Lanka. In the USA, from near Golden, Jefferson County, Colorado; in Maine, at Topsham, Sagadahoc County, from Paris, Norway, and Hartford, Oxford County, and elsewhere.