Coral (Calcareous) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Coral (Calcareous)

Coral has been prized throughout history for its natural beauty. Like pearl, coral is also an organic gem consisting of more than 90% calcium carbonate. All coral consists of the remains of skeleton-like support structures that were built by colonies of very small marine animals, known as coral polyps. Proteinaceous coral differs from calcareous coral because it is made up of strong keratin proteins.

Colors

Light Pink, Dark Red, Orange, White, Cream, Blue, Purple

  • Coral-calcareous classification

    CommonName
    Coral (Calcareous)
    Species
    NA
    Variety
    Colors
    Light Pink, Dark Red, Orange, White, Cream, Blue, Purple
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI, birefringence blink, magnification and fluorescence
    ClassificationComments
    Misnomer: polypite
  • Coral-calcareous chemistry & crystallography

    ChemicalName
    calcium carbonate
    ChemicalFormula
    CaCO3
    Synthesis
    CrystalSystem
    NA
    ChemistryClassification
    Organic
    Nature
    Natural
    Crystallinity
    Non-Crystalline
    ChemistryComments
  • Coral-calcareous optical properties

    Transparency
    Semitranslucent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.486-1.658
    Birefringence
    0.172-0.172
    OpticCharacter
    OpticSign
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish red
    LWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish red
    CCFReaction
    Pleochroism
    None
  • Coral-calcareous characteristic physical properties

    Hardness
    3.5-4
    CharacteristicComments
    Streak
    SpecificGravity
    2.6-2.7 Typical:2.65
    Toughness
    Fair
    Inclusions
    Calcareous coral has a wavy fibrous structure with polyp cavities in cross section the branches have concentric web like structure.
    Luster
    Vitreous
    Stability
    Poor
    Fracture
    Uneven, Splintery
    Cleavage
    None