Ulexite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Ulexite

Also called the "TV rock" or "television stone," ulexite is known for its unusual optical characteristics, notably its ability to transmit images through its natural fibers. A piece of writing placed underneath the stone appears on the surface of the stone! Ulexite was named for German chemist G. L. Ulex, who first correctly analyzed the species in 1850. Most specimens are milky and very poor quality, but those stones that are cut as cabochons often display a strong cat's eye effect.

Colors

White, Colorless, Gray

  • Ulexite classification

    CommonName
    Ulexite
    Species
    Ulexite
    Variety
    Colors
    White, Colorless, Gray
    AlternateNames
    TV Rock, Television Stone
    GemstoneGroups
    KeySeparations
    Appearance, RI and birefringence.
    ClassificationComments
    Ulexite will decompose in water and can be chatoyant. Ulexite is a natural fiber optic material and is called television stone because well polished stones appear to transmit writing below the stone to the surface of the stone.
  • Ulexite chemistry & crystallography

    ChemicalName
    hydrous sodium calcium borate
    ChemicalFormula
    NaCaB5O6(OH)6.5H2O
    Synthesis
    CrystalSystem
    Triclinic
    ChemistryClassification
    Borate
    Nature
    Natural
    Crystallinity
    Crystalline to Aggregate
    ChemistryComments
  • Ulexite optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: none
    OpticalComments
    RefractiveIndex
    1.491-1.52
    Birefringence
    0.029
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    None
  • Ulexite characteristic physical properties

    Hardness
    2-2.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    1.65-1.95
    Toughness
    Poor
    Inclusions
    Ulexite has a silky luster and tightly packed parallel fibers.
    Luster
    Silky
    Stability
    Poor
    Fracture
    Uneven
    Cleavage
    Perfect, in one direction, Good, in one direction, Poor, in one direction