Dravite (Tourmaline) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Dravite (Tourmaline)

Dravite is the dark yellow to brown variety of tourmaline. It is named after a deposit in modern day Slovenia near the Drave river.

Colors

Dark Yellow To Brownish Black

  • Dravite-tourmaline classification

    CommonName
    Dravite (Tourmaline)
    Species
    Dravite
    Variety
    Colors
    Dark Yellow To Brownish Black
    AlternateNames
    GemstoneGroups
    Tourmaline
    KeySeparations
    appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity
    ClassificationComments
    Named for the river Drau in the Republic of Slovenia.Dark stones might have a birefringence as high as 0.040.Pyroelectric: development of opposite charges at the ends of a tourmaline crystal due to change in temperature. Piezoelectric: development of opposite charges at the ends of a tourmaline crystal when placed under stress.
  • Dravite-tourmaline chemistry & crystallography

    ChemicalName
    Sodium magnesium boro-aluminum silicate hydroxide
    ChemicalFormula
    Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Dravite-tourmaline optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: moderate fire Value: 0.017
    OpticalComments
    RefractiveIndex
    1.614-1.666
    Birefringence
    0.014-0.032
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert to weak
    LWUV: Inert to weak
    CCFReaction
    Pleochroism
    Dichroic, strong pale yellow to colorless and yellow, green, or brown
  • Dravite-tourmaline characteristic physical properties

    Hardness
    7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3-3.26 Typical:3.06
    Toughness
    Good
    Inclusions
    Dravite is a Type II 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