Staurolite (twinned) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Staurolite (twinned)

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.

Colors

Opaque Brown To Black

  • Staurolite-twinned classification

    CommonName
    Staurolite (twinned)
    Species
    Staurolite
    Variety
    Staurolite Crystal
    Colors
    Opaque Brown To Black
    AlternateNames
    Cross Stones, Fairy Crosses
    GemstoneGroups
    KeySeparations
    Appearance of twins, RI and birefringence
    ClassificationComments
    Twinned crystals are 90o or 60o from each other
  • Staurolite-twinned chemistry & crystallography

    ChemicalName
    iron aluminum silicate hydroxide
    ChemicalFormula
    (Fe,Mg,Zn)2Al9(Si,Al)4O22(OH)2
    Synthesis
    CrystalSystem
    Monoclinic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Aggregate
    ChemistryComments
  • Staurolite-twinned optical properties

    Transparency
    Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.736-1.746
    Tolerance:(+0.015/-0.015)
    Birefringence
    0.009-0.015
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Unobservable
  • Staurolite-twinned characteristic physical properties

    Hardness
    7-7.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.65-3.79 Typical:3.71
    Toughness
    Fair
    Inclusions
    Luster
    Vitreous
    Stability
    Fracture
    Conchoidal, Uneven
    Cleavage
    Good, in one direction