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

Apatite (Cat's-Eye)

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case apatite. 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 throughout the crystal, scattering and reflecting light back to the viewer as a thin line. Chatoyancy is the only known phenomenon seen in apatite. The most common colors for cat's eye apatite are bluish green, green and yellow. Brazil and Sri Lanka are the principal sources of chatoyant apatite, although it may also be found in Madagascar and Tanzania.

Colors

Bluish Green To Yellowish Green

  • Apatite-cats-eye classification

    CommonName
    Apatite (Cat's-Eye)
    Species
    Apatite
    Variety
    Cat's-Eye Apatite
    Colors
    Bluish Green To Yellowish Green
    AlternateNames
    Fluorapatite
    GemstoneGroups
    KeySeparations
    RI, spectrum, fluorescence and SG
    ClassificationComments
    Sometimes a distorted optic figure is observed and can be mistaken for a biaxial figure. Most gemstones are Ca5(PO4)3F Calcium Fluroro Phosphate
  • Apatite-cats-eye chemistry & crystallography

    ChemicalName
    calcium phosphate with fluorine, chlorine or hydroxyl group
    ChemicalFormula
    Ca5(PO4)3(F,OH,Cl)
    Synthesis
    CrystalSystem
    Hexagonal
    ChemistryClassification
    Phosphate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Apatite-cats-eye optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: weak fire Value: 0.013
    OpticalComments
    RefractiveIndex
    1.634-1.638
    Tolerance:(+0.012/-0.006)
    Birefringence
    0.002-0.008
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    Unobservable
  • Apatite-cats-eye characteristic physical properties

    Hardness
    5
    CharacteristicComments
    Streak
    White To Yellow-Gray
    SpecificGravity
    3.13-3.23 Typical:3.18
    Toughness
    Fair
    Inclusions
    Apatite is a type II stone. Fairly well defined chatoyant band that is made up of finer tubular inclusions than cat's-eye tourmaline.
    Luster
    Vitreous
    Stability
    Fair
    Fracture
    Conchoidal, Uneven
    Cleavage
    Poor, in two directions