Natural Freshwater Pearl Gemstone & Information | Gemopedia by JTV | Gemopedia™

Natural Freshwater Pearl

Natural freshwater pearls occur in freshwater mollusks without the intervention of humans. These pearls are beautiful accidents of nature caused by an irritant that becomes lodged inside the mollusk. The animal naturally coats the irritant with nacre to protect its sensitive internal tissues, creating a pearl. Natural freshwater pearls are rare and are usually found by fishermen harvesting the mollusks.

Colors

White, Cream, Golden, Silver, Gray, Brown, Black

  • Natural-freshwater-pearl classification

    CommonName
    Natural Freshwater Pearl
    Species
    NA
    Variety
    Natural Freshwater Pearl
    Colors
    White, Cream, Golden, Silver, Gray, Brown, Black
    AlternateNames
    GemstoneGroups
    KeySeparations
    refractive index, birefringence blink, specific gravity and magnification. A "tooth test" is commonly used in which a pearl is rubbed against a tooth; if gritty, this is an indication that the surface is nacre, versus plastic and glass imitations that feel smooth. X-rays are the only nondestructive test to confirm natural versus cultured origin.
    ClassificationComments
  • Natural-freshwater-pearl chemistry & crystallography

    ChemicalName
    calcium carbonate + conchiolin and water
    ChemicalFormula
    CaCO3
    Synthesis
    CrystalSystem
    NA
    ChemistryClassification
    Organic
    Nature
    Natural
    Crystallinity
    Aggregate
    ChemistryComments
  • Natural-freshwater-pearl optical properties

    Transparency
    Translucent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.53-1.685
    Birefringence
    0.155
    OpticCharacter
    NA
    OpticSign
    NA
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    None
  • Natural-freshwater-pearl characteristic physical properties

    Hardness
    3.5-4
    CharacteristicComments
    Streak
    SpecificGravity
    2.66-2.78
    Toughness
    Fair
    Inclusions
    Natural freshwater pearls will have an iridescent surface. If the pearl is drilled you can inspect the hole to look for lack of bead nucleus.
    Luster
    Pearly
    Stability
    Poor
    Fracture
    Uneven
    Cleavage
    None