Apatite (Cat's-Eye) Gemstone & Information | Gemopedia by JTV | Gemopedia™
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.
Bluish Green To Yellowish Green
Apatite-cats-eye classificationCommonNameApatite (Cat's-Eye)SpeciesApatiteVarietyCat's-Eye ApatiteColorsBluish Green To Yellowish GreenAlternateNamesFluorapatiteGemstoneGroupsKeySeparationsRI, spectrum, fluorescence and SGClassificationCommentsSometimes 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 & crystallographyChemicalNamecalcium phosphate with fluorine, chlorine or hydroxyl groupChemicalFormulaCa5(PO4)3(F,OH,Cl)SynthesisCrystalSystemHexagonalChemistryClassificationPhosphateNatureNaturalCrystallinityCrystallineChemistryComments
Apatite-cats-eye optical propertiesTransparencyTransparent - TranslucentDispersionStrength: weak fire Value: 0.013OpticalCommentsRefractiveIndex1.634-1.638
Tolerance:(+0.012/-0.006)Birefringence0.002-0.008OpticCharacterUniaxialOpticSignNegativePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Variable
Apatite-cats-eye characteristic physical propertiesHardness5CharacteristicCommentsStreakWhite To Yellow-GraySpecificGravity3.13-3.23 Typical:3.18ToughnessFairInclusionsApatite is a type II stone. Fairly well defined chatoyant band that is made up of finer tubular inclusions than cat's-eye tourmaline.LusterVitreousStabilityFairFractureConchoidal, UnevenCleavagePoor, in two directions