Tourmaline Gemstone & Information | Gemopedia by JTV | Gemopedia™
Once proposed to be the national gemstone of the United States, tourmaline is found all over the world and in a variety of colors. Tourmaline is the most colorful of all gemstones because, according to an ancient Egyptian legend, it passed through a rainbow on its journey to Earth and brought all of the colors of the rainbow with it. Tourmaline is a mineral group comprised of multiple species of complex borosilicates. Lovingly referred to by mineralogists as the garbage can mineral, its crystal structure allows for the incorporation of a wide range of elements, many of which cause the stunning color varieties and spectacular zoning of tourmaline, including copper, manganese, iron, and titanium. Major tourmaline species include liddicoatite, dravite, uvite, schorl, and elbaite.
Light To Strong Pink, Orangy Red, Red, Purplish Red, Purple, Inky Blue, Blue, Bluish Violet, Violet, Greenish Blue, Light To Dark Green-Blue To Yellowish Green, Dark Green, Yellow, Orange, Brown, Dark Brown, Black, Rarely Colorless
Tourmaline classificationCommonNameTourmalineSpeciesElbaite, Dravite, SchorlVarietyColorsLight To Strong Pink, Orangy Red, Red, Purplish Red, Purple, Inky Blue, Blue, Bluish Violet, Violet, Greenish Blue, Light To Dark Green-Blue To Yellowish Green, Dark Green, Yellow, Orange, Brown, Dark Brown, Black, Rarely ColorlessAlternateNamesAchroite, Bi-Color Or Parti-Colored, Chrome Tourmaline, Dravite, Elbaite, Fluor-Buergerite, Indicolite, Liddicoatite, Povondtaite, ParaBa Tourmaline, Rubellite, Schorl, Uvite, Verdelite, WatermelonGemstoneGroupsKeySeparationsappearance, 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. Misnomers: Brazilian sapphire-blue tourmaline; Brazilian emerald, Ceylonese peridot-green tourmaline. Achroite: colorlessBi-color or parti-colored: tourmaline with two colors and multiple colors. Chrome tourmaline: fine intense green usually colored by chrome or vanadium. Dravite: yellow or brown tourmaline. Elbaite: a sodium lithium aluminum tourmaline species. Fluor-buergerite: bronzish-brown to dark-brown to almost black with bronze schiller. Indicolite or indigolite: violetish blue to greenish blue. Liddicoatite: a calcium lithium tourmaline species. Povondtaite: dark brown, brownish black to black with resinous luster. Paraba tourmaline: a neon blue to green colored cuprian Elbaite tourmaline originally found in the Brazilian State of Paraiba. Rubellite: deep pink to red stones. Schorl: black, brownish black or blueish black stones. Uvite: a calcium magnesium aluminum tourmaline species. Verdelite: dark green,yellowish green, brownish green to blueish green. Watermelon: pink center with green edges. Birefringence is typically around 0.020 but dark material can be up to 0.040 October birthstone. 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.
Tourmaline chemistry & crystallographyChemicalNamecomplex boro-silicate of Al, Mg and FeChemicalFormula(Ca,K,Na)(Al,Fe,Li,Mg,Mn)3(Al,Cr,Fe,V)6(BO3)Si6O18(OH,F)4SynthesisCrystalSystemTrigonalChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Tourmaline optical propertiesTransparencyTransparent - OpaqueDispersionStrength: weak fire Value: 0.017OpticalCommentsRefractiveIndex1.624-1.644
Tolerance:-1.22222222222222Birefringence0.018-0.04OpticCharacterUniaxialOpticSignNegativePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert to weak red to violet
LWUV: Inert to weak red to violetCCFReactionPleochroismDichroic, moderate to strong, varying shades of body color
Tourmaline characteristic physical propertiesHardness7-7.5CharacteristicCommentsStreakWhiteSpecificGravity3-3.26 Range:0.2/-0.06 Typical:3.06ToughnessFairInclusionsGreen tourmaline is a type I clarity stone. Blue, purple, red, orange, yellow and bi-color or parti-colored tourmaline is a type II clarity stone. Red and watermelon tourmaline are type III clarity stones. Tourmaline might contain tube-like 2-phase inclusions running parallel to crystal's principle axis, film-like, irregular or long and thin liquid inclusions, angular thin reflective inclusions, gas inclusions in net-like pattern, parallel oriented hollow tubes, needles.LusterVitreousStabilityVery GoodFractureConchoidalCleavagePoor, in two directions