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

Star Garnet

Star garnet 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".

Colors

Light To Dark Purplish Red To Reddish Purple

  • Star-garnet classification

    CommonName
    Star Garnet
    Species
    Pyrope-Almandite
    Variety
    Star Garnet
    Colors
    Light To Dark Purplish Red To Reddish Purple
    AlternateNames
    Star Rhodolite
    GemstoneGroups
    Garnet
    KeySeparations
    refractive index, SR nature and spectrum. Color is also helpful. Stones with SG lower than 3.8 and a RI lower than 1.76 are pyrope and those with higher SG are almandine.
    ClassificationComments
    Stone are only star rhodolite if there is a purple component to the color.
  • Star-garnet chemistry & crystallography

    ChemicalName
    magnesium iron aluminum silicate
    ChemicalFormula
    ((Mg,Fe)3Al2(SiO4)3)
    Synthesis
    CrystalSystem
    Cubic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Star-garnet optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: moderate fire Value: 0.026
    OpticalComments
    RefractiveIndex
    1.75-1.78
    Birefringence
    0-0
    OpticCharacter
    NA
    OpticSign
    NA
    PolariscopeReaction
    Singly Refractive (SR) With ADR
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    None
  • Star-garnet characteristic physical properties

    Hardness
    7-7.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.74-3.94 Typical:3.84
    Toughness
    Good
    Inclusions
    Pyrope-almandite garnet is a type II clarity stone. Needle like inclusions produce 4 to 6 rayed stars and will sometimes show both in well cut stones. Stones might have zircon crystals with stain halos and irregular rounded included crystals that might be zircon or apatite.
    Luster
    SubAdamantine
    Stability
    Good
    Fracture
    Conchoidal
    Cleavage
    None