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16.12: Chrysoberyl

  • Page ID
    4327
  • Chrysoberyl
    Chemical composition BeAl2O4
    Crystal system Orthorombic
    Habit Pseudo-hexagonal twins
    Cleavage Weak to moderate
    Fracture Conchoidal to uneven
    Hardness 8.5
    Optic nature Biaxial +
    Refractive index 1.74-1.75
    Birefringence 0.009
    Dispersion Low, 0.014
    Specific gravity 3.72
    Lustre Bright vitreous
    Pleochroism Moderate to strong

    Figure \(\PageIndex{1}\): Chrysoberyl
    Photo courtesy of John Huff, gemcollections.com

    Chrysoberyl image gallery

    Chrysoberyl is a beryllium aluminum oxide, not at all related to the mineral beryl, which is a silicate. Chrysoberyl can occur in various shades of green, yellow, brown, red, and occasionally blue. The most valuable varieties of chrysoberyl are alexandrite, and cat's eye. Cat's eye was long admired in the orient for its chatoyant character, but it wasn't popular in the West until the late 1800s. The third and most common variety of chrysoberyl is a transparent greenish yellow stone. It was very popular in Victorian and Edwardian jewelry. Cat's eye is believed to protect one from evil spirits or the evil eye. According to the Hindus, the stone would preserve your health and guard against poverty. In Asia, it was thought that if you pressed a cat's eye between your own eyes it would enhance your foresight.

    Phenomena

    Cat's-eyes

    File:ChrysCatEye.gif

    Figure \(\PageIndex{2}\): Cat's Eye Chrysoberyl
    Photo courtesy of The Gem Trader

    G&G Articles on Chrysoberyl 1934-1980

    The GIA has published all the G&G's from 1934 until 1980 online. The organization of the list by subject was done by Joseph Gill.

    • Jan. 1934, Chrysoberyl, p. 9, 2pp.
    • Winter 1937, A grayish-green star chrysoberyl, p. 130, 1p.
    • Fall 1945, A 115 ct. star chrysoberyl (non-gem quality), by Anderson, p. 252, 2pp.
    • Spring 1949, The Origin of Alexandrite Color Change, p. 143, 3pp.
    • Spring 1949, Chrysoberyl, p. 147, 1p.
    • Fall 1953, Inclusions in Yellow Chrysoberyl, by Webster, p. 343, 4pp.
    • Spring 1954, Separating yellow chrysoberyl and yellow corundum, p. 32, 1p.
    • Spring 1959, A 45 ct., a 12 ct., and a 50 ct. alexandrite, p. 264, 1p.
    • Summer 1960, A 4-rayed star brown chrysoberyl, p. 62, 1p.
    • Winter 1963, A cat's-eye alexandrite, p. 104, 2pp.
    • Fall 1964, Synthetic alexandrite made, p. 216, 1p.
    • Fall 1967, Cat's-Eye Doublet, p. 215, 2pp.
    • Summer 1970, High-Property Cat's-Eye (R.I. 1.76–1.77), and absorption spectrum, p. 184, 2pp.
    • Winter 1972, Synthetic alexandrite, introduced to the market by Creative Crystals, Inc., Danville, Calif., p. 102, 3pp.
    • Winter 1972, Chrysoberyl cat's-eye, proved to be natural, p. 113, 1p.
    • Winter 1972, Fine cat's-eye glass with milk and honey effect, p. 108,
    • Spring 1973, Fine cat's-eye glass and optic fibers with milk and honey effect, p. 136, 3pp.
    • Winter 1974, A new synthetic alexandrite by the Czochralski Method, p. 367, 3pp.
    • Summer 1976, A very rare 4-ray star cat's-eye chrysoberyl, p. 170, 1p.
    • Fall 1976, Alexandrite from Lake Manyara, Tanzania, by Gübelin, p. 203, 11 pp., with bibliography
    • Fall 1976, African alexandrites?, p. 211, 3pp.
    • Spring 1979, Natural & Synthetic Alexandrites, p. 148, 1p.
    • Spring 1980, Fiber optic cat’s-eye imitation, p. 278, 1p.
    • Summer 1980, A Giant Chrysoberyl Crystal, p. 320, 2pp.