Quartz (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 quartz gems. 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.
Brownish Yellow, Brownish Green, Green-Yellow To Gray
Quartz-cats-eye classificationCommonNameQuartz (Cat's-Eye)SpeciesQuartzVarietyCat's-Eye QuartzColorsBrownish Yellow, Brownish Green, Green-Yellow To GrayAlternateNamesGemstoneGroupsKeySeparationsAppearance, RI and SG. Magnification and fluorescence might be helpful. A bull's-eye optic figure is determinative for quartz; may also show Airy's spiral optic figure and Brazil-law twinning under crossed polarizing filters.ClassificationComments
Quartz-cats-eye chemistry & crystallographyChemicalNamesilicon dioxide (aka silica)ChemicalFormulaSiO2SynthesisCrystalSystemTrigonalChemistryClassificationSilicateNatureNaturalCrystallinityCrystalline to AggregateChemistryComments
Quartz-cats-eye optical propertiesTransparencySemitransparent - TranslucentDispersionOpticalCommentsRefractiveIndex1.544-1.553
Tolerance:very constantBirefringence0.009OpticCharacterUniaxialOpticSignPositivePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert
Quartz-cats-eye characteristic physical propertiesHardness7CharacteristicCommentsStreakSpecificGravity2.64-2.69 Typical:2.66ToughnessGoodInclusionsCat's-eye quartz has parallel needle-like inclusions that are typically asbestos or rutile.LusterVitreousStabilityGoodFractureConchoidalCleavageNone