Schorl Gemstone & Information | Gemopedia by JTV | Gemopedia™

Schorl

Schorl is the most common species of tourmaline, however, it is not as commonly faceted as its brightly colored brothers and sisters because of its black color. Well-formed schorl crystals make striking mineral specimens and long, thin schorl crystals are frequently found in quartz, called "tourmalinated quartz."

Colors

Very Dark Brown, Very Dark Green, Blueish Black To Black

  • Schorl classification

    CommonName
    Schorl
    Species
    Tourmaline
    Variety
    Schorl
    Colors
    Very Dark Brown, Very Dark Green, Blueish Black To Black
    AlternateNames
    GemstoneGroups
    KeySeparations
    appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity
    ClassificationComments
    Crystal habit is prismatic and may be 3, 6 or 9-sided; often a triangular prism with convex faces, and often long and heavily striated parallel to the c axis. Pyramidal terminations are common. Tourmaline is part of an isomorphous series.Most common form of tourmaline.Dark material 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.
  • Schorl chemistry & crystallography

    ChemicalName
    complex boro-silicate of Al, Mg and Fe
    ChemicalFormula
    Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Schorl optical properties

    Transparency
    Semitranslucent - Opaque
    Dispersion
    Strength: moderate fire Value: 0.017
    OpticalComments
    RefractiveIndex
    1.635-1.672
    Birefringence
    0.018-0.025
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Pleochroism
    Unobservable
  • Schorl characteristic physical properties

    Hardness
    7-7.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3-3.26 Range:0.2/-0.06 Typical:3.06
    Toughness
    Good
    Inclusions
    Schorl often has tube-like 2-phase inclusions running parallel to crystal's principle axis, film-like, irregular or thread-like liquid inclusions, angular thin film mirror-like inclusions, gas inclusions in mesh-like pattern, parallel oriented hollow tubes or needles.
    Luster
    Vitreous
    Stability
    Very Good
    Fracture
    Conchoidal, Uneven
    Cleavage
    Poor, in two directions