Onyx Marble Gemstone & Information | Gemopedia by JTV | Gemopedia™

Onyx Marble

The term onyx marble is a misnomer sometimes used to describe a rock made up of alternating layers of different colored calcite. The alternating bands closely resemble those that can form in onyx, however, onyx is a silicate mineral and calcite is a carbonate and their physical properties are dramatically different.

Colors

Various

  • Onyx-marble classification

    CommonName
    Onyx Marble
    Species
    Calcite
    Variety
    Onyx Marble
    Colors
    Various
    AlternateNames
    Marble Onyx, Banded Calcite
    GemstoneGroups
    Calcite
    KeySeparations
    cleavage, refractive index, birefringence (using distant vision method), specific gravity. Use birefrigence blink method.
    ClassificationComments
    When banded and Translucent to opaque, the calcite variety is referred to as "onyx marble," although some disfavor this nomenclature. Misnomers: Oriental alabaster, Mexican onyx and California onyx. Type of limestone used for ornamental objects.
  • Onyx-marble chemistry & crystallography

    ChemicalName
    calcium carbonate
    ChemicalFormula
    CaCO3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Carbonate
    Nature
    Natural
    Crystallinity
    Aggregate
    ChemistryComments
  • Onyx-marble optical properties

    Transparency
    Semitranslucent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.486-1.658
    Birefringence
    0.172-0.172
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    None
  • Onyx-marble characteristic physical properties

    Hardness
    3
    CharacteristicComments
    Streak
    Varies By Color
    SpecificGravity
    2.65-2.75 Range:+/-0.05 Typical:2.7
    Toughness
    Varies
    Inclusions
    Onyx marble is a banded granular aggregate and is often dyed.
    Luster
    Vitreous
    Stability
    Fair
    Fracture
    Uneven, Granular, Splintery
    Cleavage
    Perfect, in three directions