Forsterite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Forsterite

Forsterite is a colorless to greenish transparent member of the olivine mineral family, which also includes peridot. Forsterite has a heavy magnesium chemical composition and large crystals are not common, but highly sought after by collectors.

Colors

Colorless, Green, Yellow Green, Yellow, White

  • Forsterite classification

    CommonName
    Forsterite
    Species
    Forsterite
    Variety
    Colors
    Colorless, Green, Yellow Green, Yellow, White
    AlternateNames
    GemstoneGroups
    Olivine
    KeySeparations
    RI and birefringence
    ClassificationComments
    Forsterite is in the olivine group with peridot. If the stone is bright green it is probably peridot if the stone is colorless it is forsterite.
  • Forsterite chemistry & crystallography

    ChemicalName
    magnesium silicate
    ChemicalFormula
    Mg2SiO4
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Forsterite optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: none
    OpticalComments
    RefractiveIndex
    1.635-1.671
    Birefringence
    0.034-0.035
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert to weak greenish yellow
    LWUV: Inert to weak orangy white
    CCFReaction
    Pleochroism
    Dichroic, unobservable or weak, varying shades of body color
  • Forsterite characteristic physical properties

    Hardness
    6.5-7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.23-3.26 Typical:3.2
    Toughness
    Poor
    Inclusions
    Luster
    Vitreous
    Stability
    Fracture
    Conchoidal
    Cleavage
    Good, in two directions