Demantoid Garnet (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 demantoid garnet. 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. Demantoid garnets that feature a cat's eye are rare.
Light To Dark Green To Yellow-Green
Demantoid-garnet-cats-eye classificationCommonNameDemantoid Garnet (Cat's-Eye)SpeciesAndraditeVarietyCat's-Eye Demantoid GarnetColorsLight To Dark Green To Yellow-GreenAlternateNamesGemstoneGroupsGarnetKeySeparationsOTL RI, spectrum and SGClassificationComments
Demantoid-garnet-cats-eye chemistry & crystallographyChemicalNamecalcium iron silicateChemicalFormulaCa3Fe2(SiO4)3SynthesisCrystalSystemCubicChemistryClassificationSilicateNatureNaturalCrystallinityCrystalline to AggregateChemistryComments
Demantoid-garnet-cats-eye optical propertiesTransparencySemitransparent To OpaqueDispersionStrength: strong fire Value: 0.57OpticalCommentsRefractiveIndex1.888-0BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionSingly Refractive (SR) With ADRFluorescenceSWUV: Inert
Demantoid-garnet-cats-eye characteristic physical propertiesHardness6.5-7CharacteristicCommentsStreakSpecificGravity3.81-3.87 Typical: 3.84ToughnessPoorInclusionsCat's-eye demantoid garnet is type II clarity stone. Chatoyancy is caused by parallel needles. Due to the stones low mohs hardness it might have scratches and abrasions. Fibrous asbestos "horsetail inclusions" in Russian material. Stress fractures in Namibian stones.LusterSubAdamantineStabilityGoodFractureConchoidal, UnevenCleavageNone