Iceland Spar Gemstone & Information | Gemopedia by JTV | Gemopedia™

Iceland Spar

The colorless, transparent variety of calcite is called "Iceland spar," an important variety for its use in optics, including gemological dichroscopes. Originally discovered in Iceland, gems are most often sold as cleavage pieces that beautifully demonstrate calcite's unique birefringence, or double refraction. Because it is a natural polarizing filter, many believe it was used as a navigational tool by ancient Vikings.

Colors

Colorless, Possible Very Pale Yellow

  • Iceland-spar classification

    CommonName
    Iceland Spar
    Species
    Calcite
    Variety
    Iceland Spar
    Colors
    Colorless, Possible Very Pale Yellow
    AlternateNames
    Icelandic Spar
    GemstoneGroups
    Calcite
    KeySeparations
    cleavage, refractive index, birefringence, strong doubling (if transparent), specific gravity. Use birefringence blink method.
    ClassificationComments
    When colorless and transparent, the variety is called "Iceland spar," an important variety for its use in dichroscopes. Most often sold as cleavage pieces.
  • Iceland-spar chemistry & crystallography

    ChemicalName
    calcium carbonate
    ChemicalFormula
    CaCO3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Carbonate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Iceland-spar optical properties

    Transparency
    Transparent
    Dispersion
    Strength: moderate fire Value: 0.017
    OpticalComments
    RefractiveIndex
    1.486-1.658
    Birefringence
    0.172-0.172
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    None
  • Iceland-spar characteristic physical properties

    Hardness
    3
    CharacteristicComments
    Streak
    SpecificGravity
    2.65-2.75 Range:+/-0.05 Typical:2.7
    Toughness
    Poor
    Inclusions
    Iceland spar is identified by strong eye visible doubling and might show adularescence.
    Luster
    Vitreous
    Stability
    Fair
    Fracture
    Uneven, Granular, Splintery
    Cleavage
    Perfect, in three directions