Sapphire (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 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.
Blue, If Any Other Color Designate By Color; Black Sapphires Can Be Black, Dark Brown, Dark Blue, Dark Green
Sapphire-cats-eye classificationCommonNameSapphire (Cat's-Eye)SpeciesCorundumVarietyCat's-Eye SapphireColorsBlue, If Any Other Color Designate By Color; Black Sapphires Can Be Black, Dark Brown, Dark Blue, Dark GreenAlternateNamesGemstoneGroupsKeySeparationsappearance, RI and magnificationClassificationCommentsStone usually cut as cabochons. Black stones are often twinned and susceptible to parting.
Sapphire-cats-eye chemistry & crystallographyChemicalNamealuminum oxideChemicalFormulaAl2O3SynthesisCrystalSystemTrigonalChemistryClassificationOxideNatureNaturalCrystallinityCrystallineChemistryComments
Sapphire-cats-eye optical propertiesTransparencySemitransparent - OpaqueDispersionStrength: weak fire Value: 0.018OpticalCommentsRefractiveIndex1.762-1.77
Tolerance:(+0.009/-0.005)Birefringence0.008-0.01OpticCharacterUniaxialOpticSignNegativePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: 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: inertCCFReactionPleochroismUnobservable
Sapphire-cats-eye characteristic physical propertiesHardness9CharacteristicCommentsStreakWhiteSpecificGravity4.1-3.95 Typical:4ToughnessVariesInclusionsCat'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.LusterSubAdamantineStabilityVery GoodFractureConchoidalCleavageNone