Prase Gemstone & Information | Gemopedia by JTV | Gemopedia™

Prase

Prase is a dull green to yellowish green variety of chalcedony, a cryptocrystalline quartz. It is commonly fashioned en cabochon to show off its leek-green color. Prase can be confused with chrysoprase since they are very similar in appearance, but a darker, less saturated color is typically indicative of prase.

Colors

Dark Green With White, Yellowish Spots

  • Prase classification

    CommonName
    Prase
    Species
    Chalcedony
    Variety
    Prase
    Colors
    Dark Green With White, Yellowish Spots
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI, SG, appearance and fracture
    ClassificationComments
    Prase is less saturated in color than chrysoprase and its translucent to semi transparent nature separates it from plasma.
  • Prase chemistry & crystallography

    ChemicalName
    silicon dioxide (aka silica)
    ChemicalFormula
    SiO2
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Polycrystalline
    ChemistryComments
  • Prase optical properties

    Transparency
    Transparent - Semitranslucent
    Dispersion
    Strength: none
    OpticalComments
    RefractiveIndex
    1.535-1.539
    Birefringence
    0.004-0.004
    OpticCharacter
    Uniaxial
    OpticSign
    Positive
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    None
  • Prase characteristic physical properties

    Hardness
    6.5-7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.55-2.7 Typical:2.6
    Toughness
    Excellent
    Inclusions
    Prase's green color is due to chlorite inclusions, the grayish green color is due actinolite fibers and the blue color is due to crocidolite fibers.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal, Granular
    Cleavage
    None