Chrysoberyl (Cat's-Eye) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Chrysoberyl (Cat's-Eye)

The term cat's eye is used to describe a phenomenal optical property in gemstones, but in this case, chrysoberyl. Known as chatoyancy, this effect appears as a bright, narrow slit--similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by the presence of parallel fibrous or needle-like inclusions that interfere with the passage of light through the crystal, scattering and reflecting light back to the viewer as a thin line.

Colors

Yellow To Yellowish Green, Grayish Green, Brown To Brownish Yellow

  • Chrysoberyl-cats-eye classification

    CommonName
    Chrysoberyl (Cat's-Eye)
    Species
    Chrysoberyl
    Variety
    Cat's-Eye Chrysoberyl
    Colors
    Yellow To Yellowish Green, Grayish Green, Brown To Brownish Yellow
    AlternateNames
    Cymophane, Cat's-Eye
    GemstoneGroups
    KeySeparations
    refractive index, specific gravity, appearance and spectrum. Spectrum should reflect a strong diagnostic band at 444nm.
    ClassificationComments
    Phenomenal chrysoberyl may exhibit chatoyancy, in which case it is classified as "cat's-eye chrysoberyl." Cymophane will show a broad sheen instead of a distinct cat's-eye. Most often seen with yellowish green to orangy yellow background with strong silvery white cat's-eye.Cat's-eye chrysoberyl is the only chatoyant stone allowed to be called by only the name cat's-eye. Rare stones might show 4 rayed stars.
  • Chrysoberyl-cats-eye chemistry & crystallography

    ChemicalName
    beryllium aluminum oxide
    ChemicalFormula
    BeAl2O4
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Chrysoberyl-cats-eye optical properties

    Transparency
    Semitransparent - Translucent
    Dispersion
    Strength: weak fire Value: 0.015
    OpticalComments
    RefractiveIndex
    1.746-1.755
    Tolerance:(+0.004/-0.006)
    Birefringence
    0.008-0.01
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Unobservable
  • Chrysoberyl-cats-eye characteristic physical properties

    Hardness
    8.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.71-3.75 Range:+/-0.02 Typical:3.73
    Toughness
    Varies
    Inclusions
    Cat's-eye chrysoberyl will have parallel rutile needles or hollow growth tubes parallel to the c-axis that have give the appearance of silk. Stone can contain fingerprints or liquid inclusions and have angular included crystals. Stone might show twinning
    Luster
    Bright Vitreous
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    Good, in one direction, Poor, in two directions