Star Corundum (Lattice-Diffused) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Star Corundum (Lattice-Diffused)

Corundum with star induced by lattice diffusion has been treated with a heat treatment at high temperatures with beryllium that deeply penetrates the gem material to alter the color. This gem 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 narrow bands of light.

Colors

Blue

  • Star-corundum-lattice-diffused classification

    CommonName
    Star Corundum (Lattice-Diffused)
    Species
    Corundum
    Variety
    Lattice Diffused Star Corundum
    Colors
    Blue
    AlternateNames
    Corundum With Star Induced By Lattice Diffusion
    GemstoneGroups
    KeySeparations
    magnification and appearance
    ClassificationComments
  • Star-corundum-lattice-diffused chemistry & crystallography

    ChemicalName
    aluminum oxide
    ChemicalFormula
    Al2O3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Star-corundum-lattice-diffused optical properties

    Transparency
    Semitransparent - Opaque
    Dispersion
    Strength: weak 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: Inert to strong red
    LWUV: weak to strong red
    CCFReaction
    Pleochroism
    Unobservable
  • Star-corundum-lattice-diffused characteristic physical properties

    Hardness
    9
    CharacteristicComments
    Streak
    White
    SpecificGravity
    4.1-3.95 Typical:4
    Toughness
    Varies
    Inclusions
    Stars that are induced by lattice diffusion will have a unnaturally sharp or well defined star. The color of the stone is confined to the surface and concentrated around the girdle edge. The stone can have color concentrations in the pits and fractures. None of the rays of the star are perpendicular to the stone's hexagonal growth structure.
    Luster
    SubAdamantine
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    None