Peridot Gemstone & Information | Gemopedia by JTV | Gemopedia™

Peridot

August's birthstone, peridot, is a relatively inexpensive, beautiful gem with a pedigree dating back as far as early Egyptians. Among its accolades, peridot can count being a favorite among royals and clergy, used to adorn everything from a queen's crown to a knight's sword. Peridot jewels were actually among Cleopatra's beloved treasures, though she believed them to be emeralds, as gems were then classified solely by color. Prized for its all natural, unenhanced range of colors, peridot is the gem variety of olivine and exhibits colors ranging from golden lime greens to rich grass greens.

Colors

Green, Greenish Yellow, Brownish Green

  • Peridot classification

    CommonName
    Peridot
    Species
    Forsterite
    Variety
    Colors
    Green, Greenish Yellow, Brownish Green
    AlternateNames
    Chrysolite, Hawaiite
    GemstoneGroups
    Olivine
    KeySeparations
    refractive index, birefringence, optic character, spectrum and possibly magnification. High birefringence results often in very visible doubling of back facets under magnification.
    ClassificationComments
    Crystal habit is commonly an orthorhombic prism with vertical rhombic faces and side pinacoids. Peridot is a member of the olivine isomorphous series with forsterite (magnesium silicate) and fayalite (iron silicate) as the end members. Misnomers: evening emerald or night emerald. August birthstone.
  • Peridot chemistry & crystallography

    ChemicalName
    magnesium iron silicate
    ChemicalFormula
    (Mg,Fe)2SiO4
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Peridot optical properties

    Transparency
    Transparent
    Dispersion
    OpticalComments
    RefractiveIndex
    1.654-1.69
    Tolerance:(+0.020/-0.020)
    Birefringence
    0.035-0.038
    OpticCharacter
    Biaxial
    OpticSign
    Positive or Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Dichroic, unobservable or weak, varying shades of body color
  • Peridot characteristic physical properties

    Hardness
    6.5-7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.27-3.38 Range:0.04/-0.07 Typical:3.34
    Toughness
    Varies
    Inclusions
    Peridot is a type II clarity stone. Peridot might contain black octahedral chromite crystals. Stones might have liquid and gas inclusions that sometimes cause stress cracks that have a disk-like or "lily pad" appearance. Stones occasionally have mica flakes that give the stone a brownish hue. Stones from Pakistan often contain black ludwigite inclusions that have a hair or rod-like appearance.
    Luster
    Vitreous
    Stability
    Fair
    Fracture
    Conchoidal
    Cleavage
    Good, in two directions