Kyanite Gemstone & Information | Gemopedia by JTV | Gemopedia™
Kyanite is named for the Greek word for blue, kyanos. And what a blue! Fine Nepali kyanite can resemble the finest sapphire. Kyanite was a gem far better known to mineral collectors until more recent finds in the Kali Gandaki river region of west central Nepal, the first source to produce a significant amount of facet grade kyanite. Prior to the Nepal discoveries, Brazil was a major source of mineral specimen material, but kyanite also occurs in a variety of locations around the world. More recent kyanite discoveries have yielded additional colors, including orange and green.
Light To Dark Blue To Green; Zoned With Blue, Green, Colorless Bands
Kyanite classificationCommonNameKyaniteSpeciesKyaniteVarietyColorsLight To Dark Blue To Green; Zoned With Blue, Green, Colorless BandsAlternateNamesCyanite Or DistheneGemstoneGroupsKeySeparationsrefractive index, birefringence, optic character (kyanite is biaxial positive, it has been misstated as biaxial negative) and appearance.ClassificationCommentsFibrous structure rarely produces Cat's-eye stones.
Kyanite chemistry & crystallographyChemicalNamealuminum silicateChemicalFormulaAl2SiO5SynthesisCrystalSystemTriclinicChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Kyanite optical propertiesTransparencyTransparent - TranslucentDispersionStrength: moderate fire Value: 0.02OpticalCommentsRefractiveIndex1.716-1.731
Tolerance:(+0.004/-0.004)Birefringence0.012-0.017OpticCharacterBiaxialOpticSignPositivePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Weak red
LWUV: Weak redCCFReactionPleochroismTrichroic, moderate to strong colorless, dark blue, and violet-blue
Kyanite characteristic physical propertiesHardness5.5-7CharacteristicCommentsStreakWhiteSpecificGravity3.56-3.69 Range:0.01/-0.12 Typical:3.68ToughnessPoorInclusionsKyanite displays color zoning often in bands and may appear fibrous. Stones may contain natural inclusions.LusterVitreousStabilityFractureUnevenCleavagePerfect, in one direction, Good, in two directions