Staurolite Gemstone & Information | Gemopedia by JTV | Gemopedia™
The name staurolite comes from the Greek word stauros, meaning cross. Staurolite is prized for its twinned crystals that intersect at 60 or 90 angles forming x-like or perpendicular crosses and specimens exhibiting these forms are highly prized by collectors. Sometimes referred to respectively as St. Andrew's and Greek crosses as well as lucky cross, fairy stone or fairy cross, one legend says the crystal crosses were created by the tears of fairies whom could not help but cry when they heard of Christ's crucifixion. Staurolite is a metamorphic mineral that ranges from translucent to opaque in appearance and facetable gems are vary rare.
Reddish Brown, Blackish Brown, Yellowish Brown, Rarely Blue
Staurolite classificationCommonNameStauroliteSpeciesStauroliteVarietyFacet Grade StauroliteColorsReddish Brown, Blackish Brown, Yellowish Brown, Rarely BlueAlternateNamesGemstoneGroupsKeySeparationsAppearance of twins, RI and birefringenceClassificationCommentsTwinned crystals are 90o or 60o from each other.
Staurolite chemistry & crystallographyChemicalNameiron aluminum silicate hydroxideChemicalFormula(Fe,Mg,Zn)2Al9(Si,Al)4O22(OH)2SynthesisCrystalSystemMonoclinicChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Staurolite optical propertiesTransparencyTransparent - TranslucentDispersionStrength: moderate fire Value: 0.021OpticalCommentsRefractiveIndex1.736-1.746
Tolerance:(+0.015/-0.015)Birefringence0.009-0.015OpticCharacterBiaxialOpticSignPositivePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert
LWUV: InertCCFReactionPleochroismTrichroic, moderate yellow to red, brownish yellow, and colorless
Staurolite characteristic physical propertiesHardness7-7.5CharacteristicCommentsStreakWhiteSpecificGravity3.65-3.79 Typical:3.71ToughnessFairInclusionsLusterVitreousStabilityFractureConchoidal, UnevenCleavageGood, in one direction