Shell Gemstone & Information | Gemopedia by JTV | Gemopedia™

Shell

Shells were one of the first items used for ornamentation, and for good reason. Unique, one-of-a-kind shells have their own allure and appealing, natural beauty. Formed as the hard outer covering of many mollusks, shell is grown in layers by cells in the mantle, a skin-like tissue in the mollusk's body wall. As there are many varieties of mollusk, shells come in an endless array of shapes, sizes, and colors.

Colors

White, Gray, Brown, Yellow, Orange, Pink

  • Shell classification

    CommonName
    Shell
    Species
    NA
    Variety
    Colors
    White, Gray, Brown, Yellow, Orange, Pink
    AlternateNames
    GemstoneGroups
    KeySeparations
    Appearance, RI, birefringence blink and magnification.
    ClassificationComments
    Misnomers: Chinese cat's-eye, shell cat's-eye Helmut shell are usually carved as cameos, generally layered in two colors, white and brown or white and orangeConch shell: pink to orangeOperculum: white, green and brown with eye-like appearance
  • Shell chemistry & crystallography

    ChemicalName
    calcium carbonate, conchiolin and water
    ChemicalFormula
    CaCO3 with H2O and other organic materials
    Synthesis
    CrystalSystem
    NA
    ChemistryClassification
    Organic
    Nature
    Natural
    Crystallinity
    Non-Crystalline
    ChemistryComments
  • Shell optical properties

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

    Hardness
    3.5
    CharacteristicComments
    Streak
    SpecificGravity
    2.7-2.89 Typical:2.86
    Toughness
    Fair
    Inclusions
    Shell cameos will show concave backs due to structure of the shell. Shells might show orient and will have a parallel growth structure.Helmut shell cameos will have a straight irregular fibrous structure and concave back.Operculum is the eye-like marking on the front and spiral growth on the back of a shell.Conch shells will have a flame-like structure.
    Luster
    Greasy
    Stability
    Fracture
    Uneven, Splintery
    Cleavage
    None