Sardonyx Gemstone & Information | Gemopedia by JTV | Gemopedia™

Sardonyx

Sardonyx is a form of onyx that is made up of bands of red sard and white chalcedony. Because of its banded patterns, sardonyx has been used for years in making cameos.

Colors

Carnelian, Sard Colors With Either White, Black Banding

  • Sardonyx classification

    CommonName
    Sardonyx
    Species
    Quartz
    Variety
    Chalcedony
    Colors
    Carnelian, Sard Colors With Either White, Black Banding
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI, SG, appearance and fracture
    ClassificationComments
  • Sardonyx chemistry & crystallography

    ChemicalName
    silicon dioxide (aka silica)
    ChemicalFormula
    SiO2
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Polycrystalline
    ChemistryComments
  • Sardonyx optical properties

    Transparency
    Semitransparent - Semitranslucent
    Dispersion
    Strength: none
    OpticalComments
    RefractiveIndex
    1.535-1.539
    Birefringence
    0.004-0.004
    OpticCharacter
    Uniaxial
    OpticSign
    Positive
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    None
  • Sardonyx characteristic physical properties

    Hardness
    6.5-7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.55-2.7 Typical:2.6
    Toughness
    Excellent
    Inclusions
    Sardonyx has white and/or black bands alternating on carnelian or sard colors and this is what separates sardonyx from other calcedonies.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal, Granular
    Cleavage
    None