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

Sapphire (Cat's-Eye)

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case sapphire. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by 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

Blue, If Any Other Color Designate By Color; Black Sapphires Can Be Black, Dark Brown, Dark Blue, Dark Green

  • Sapphire-cats-eye classification

    CommonName
    Sapphire (Cat's-Eye)
    Species
    Corundum
    Variety
    Cat's-Eye Sapphire
    Colors
    Blue, If Any Other Color Designate By Color; Black Sapphires Can Be Black, Dark Brown, Dark Blue, Dark Green
    AlternateNames
    GemstoneGroups
    KeySeparations
    appearance, RI and magnification
    ClassificationComments
    Stone usually cut as cabochons. Black stones are often twinned and susceptible to parting.
  • Sapphire-cats-eye chemistry & crystallography

    ChemicalName
    aluminum oxide
    ChemicalFormula
    Al2O3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Sapphire-cats-eye optical properties

    Transparency
    Semitransparent - Opaque
    Dispersion
    Strength: weak fire Value: 0.018
    OpticalComments
    RefractiveIndex
    1.762-1.77
    Tolerance:(+0.009/-0.005)
    Birefringence
    0.008-0.01
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Blue: Inert; possibly weak chalky blue or yellowish green this might indicate heat treatmentPink: weak orangy-redOrange: usually inertYellow: weak red to orange-redGreen: inertViolet: inert or weaker to moderate red Colorless: inert to moderate red to orangeBrown: usually inert, maybe weak redBlack: inert
    LWUV: Blue: Inert; possibly red to orangePink: strong orange-redOrange: maybe strong orange red Yellow: inert to moderate orange red to orange-yellowGreen: inertViolet: inert to moderate to strong redColorless: inert to moderate red to orangeBrown: usually inert, maybe weak redBlack: inert
    CCFReaction
    Pleochroism
    Unobservable
  • Sapphire-cats-eye characteristic physical properties

    Hardness
    9
    CharacteristicComments
    Streak
    White
    SpecificGravity
    4.1-3.95 Typical:4
    Toughness
    Varies
    Inclusions
    Cat's-eye sapphire will have silk or sets of parallel rutile needles, hexagonal growth lines, color zoning, liquid , negative and mineral inclusions. Some stone might show twinning.
    Luster
    SubAdamantine
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    None