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

Star Ruby

Star ruby 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

Red, Orangy Red To Purplish Red

  • Star-ruby classification

    CommonName
    Star Ruby
    Species
    Corundum
    Variety
    Star Ruby
    Colors
    Red, Orangy Red To Purplish Red
    AlternateNames
    GemstoneGroups
    KeySeparations
    Appearance, RI and magnification
    ClassificationComments
    Stones are usually cut as cabochons.
  • Star-ruby chemistry & crystallography

    ChemicalName
    aluminum oxide
    ChemicalFormula
    Al2O3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline to Aggregate
    ChemistryComments
  • Star-ruby optical properties

    Transparency
    Semitransparent - Opaque
    Dispersion
    Strength: moderate fire Value: 0.018
    OpticalComments
    RefractiveIndex
    1.762-1.77
    Tolerance:(+0.009/-0.005)
    Birefringence
    0.008-0.01
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Weak to strong red
    LWUV: Weak to strong red
    CCFReaction
    Pleochroism
    Unobservable
  • Star-ruby characteristic physical properties

    Hardness
    9
    CharacteristicComments
    Streak
    White
    SpecificGravity
    4.1-3.95 Typical:4
    Toughness
    Varies
    Inclusions
    Star rubies will have silk or sets of parallel rutile needles that produce a 6-rayed star, hexagonal growth lines, color zoning, liquid, negative and mineral inclusions. Some stone might show twinning.
    Luster
    SubAdamantine
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    None