Schorl Gemstone & Information | Gemopedia by JTV | Gemopedia™
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."
Very Dark Brown, Very Dark Green, Blueish Black To Black
Schorl classificationCommonNameSchorlSpeciesTourmalineVarietySchorlColorsVery Dark Brown, Very Dark Green, Blueish Black To BlackAlternateNamesGemstoneGroupsKeySeparationsappearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravityClassificationCommentsCrystal 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 & crystallographyChemicalNamecomplex boro-silicate of Al, Mg and FeChemicalFormulaNa(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)SynthesisCrystalSystemTrigonalChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Schorl optical propertiesTransparencySemitranslucent - OpaqueDispersionStrength: moderate fire Value: 0.017OpticalCommentsRefractiveIndex1.635-1.672Birefringence0.018-0.025OpticCharacterUniaxialOpticSignNegativePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Variable
Schorl characteristic physical propertiesHardness7-7.5CharacteristicCommentsStreakWhiteSpecificGravity3-3.26 Range:0.2/-0.06 Typical:3.06ToughnessGoodInclusionsSchorl 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.LusterVitreousStabilityVery GoodFractureConchoidal, UnevenCleavagePoor, in two directions