Star Spinel Gemstone & Information | Gemopedia by JTV | Gemopedia™

Star Spinel

Star spinel exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. Depending on the crystal, the star may have four, six, or even twelve rays. When only one band forms, it is classified as a "cat's eye". Star spinel is highly treasured by collectors for its phenomenal quality.

Colors

Red, Violet, Purple

  • Star-spinel classification

    CommonName
    Star Spinel
    Species
    Spinel
    Variety
    Star Spinel
    Colors
    Red, Violet, Purple
    AlternateNames
    GemstoneGroups
    KeySeparations
    Appearance, RI and SG
    ClassificationComments
  • Star-spinel chemistry & crystallography

    ChemicalName
    magnesium aluminum oxide
    ChemicalFormula
    MgAl2O4
    Synthesis
    CrystalSystem
    Cubic
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline to Aggregate
    ChemistryComments
  • Star-spinel optical properties

    Transparency
    Transparent - Opaque
    Dispersion
    Strength: moderate fire Value: 0.02
    OpticalComments
    RefractiveIndex
    1.718
    Tolerance:(+0.017/-0.008)
    Birefringence
    OpticCharacter
    NA
    OpticSign
    NA
    PolariscopeReaction
    Singly Refractive (SR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    None
  • Star-spinel characteristic physical properties

    Hardness
    8
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.57-3.7 Typical:3.6
    Toughness
    Varies
    Inclusions
    Star spinels will contain needles that may show six or four rayed star. In stones cut as spheres it might be possible to see both four and six rayed stars. Stones might contain natural mineral inclusions like spinel or apatite, negative crystals in the shape of an octahedral and fingerprints.
    Luster
    SubAdamantine
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    None