Chrome Tourmaline Gemstone & Information | Gemopedia by JTV | Gemopedia™

Chrome Tourmaline

First discovered in Tanzania in the 1960's, chrome tourmaline is a fairly new addition to the vast tourmaline family. A true collector's gem, chrome tourmaline exhibits bright green color that resembles, and even rivals, that of the finest emeralds. While it is a type of green tourmaline, not all green tourmalines contain chromium and can be called chrome tourmaline. True chrome tourmaline is more highly prized, as it is a more rare occurrence for chromium to be a coloring agent, which often results in a much brighter and richer green color.

Colors

Fine Intense Green

  • Chrome-tourmaline classification

    CommonName
    Chrome Tourmaline
    Species
    Dravite
    Variety
    Chrome Tourmaline
    Colors
    Fine Intense Green
    AlternateNames
    Chromtourmaline, Chromium Tourmaline
    GemstoneGroups
    Tourmaline
    KeySeparations
    appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity
    ClassificationComments
    Stones are colored by chromium or vanadium.Dark stones might have a birefringence as high as 0.040
  • Chrome-tourmaline chemistry & crystallography

    ChemicalName
    complex boro-silicate of Al, Mg and Fe
    ChemicalFormula
    Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Chrome-tourmaline optical properties

    Transparency
    Transparent - Opaque
    Dispersion
    Strength: moderate fire Value: 0.017
    OpticalComments
    RefractiveIndex
    1.624-1.624
    Tolerance:-1.22222222222222
    Birefringence
    0.018-0.02
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert to weak
    LWUV: Inert to weak
    CCFReaction
    Reddish
    Pleochroism
    Dichroic, strong dark green and yellow-green
  • Chrome-tourmaline characteristic physical properties

    Hardness
    7-7.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3-3.26 Typical:3.06
    Toughness
    Good
    Inclusions
    Chrome tourmaline is a type I clarity stone. Stones might have liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning.
    Luster
    Vitreous
    Stability
    Very Good
    Fracture
    Conchoidal, Uneven
    Cleavage
    Poor, in two directions