The Tourmaline Group

Tourmaline Classification Scheme
(as proposed by Hawthorne and Henry (1999))

 Buergerite  NaFe3+3Al6(BO3)3Si6O18(O)3(OH) 
 Chromdravite  NaMg3Cr6(BO3)3Si6O18(OH)4
 Dravite  NaMg3Al6(BO3)3Si6O18(OH)4
 Elbaite   Na(Li1.5Al1.5)Al6(BO3)3Si6O18(OH)4
 Foitite   [][Fe2+2Al]Al6(BO3)3Si6O18(OH)4
 Hydroxy-feruvite  CaFe2+3[Al5Mg](BO3)3Si6O18(OH)4
 Magnesiofoitite   [][Mg2Al]Al6(BO3)3Si6O18(OH)4
 Liddicoatite  Ca(Li2Al)Al6(BO3)3Si6O18(OH)3F
 Olenite  NaAl3Al6(BO3)3Si6O18(O)3(OH) 
 Povondraite  NaFe3+3[Fe3+4Mg2](BO3)3Si6O18(OH)3O
 Rossmanite  [](LiAl2)Al6(BO3)3Si6O18(OH)4
 Schorl  NaFe2+3Al6(BO3)3Si6O18(OH)4
 Uvite  CaMg3[Al5Mg](BO3)3Si6O18(OH)3F

    [] in these formulas refers to a vacant cation site (the X site)

Tourmaline colors

The color of tourmaline originates from the metal ions (Fe, Mn, Cr, V, Ti, Cu) in its structure. Colors come both from light absorption by the individual ions (eg, Fe2+ or Cr3+) and by light absorbed by interactions between ions (eg, Fe2+-Ti4+, Mn2+-Ti4+ or Fe2+-Fe3+ intervalence charge transfer [IVCT]).

Blue color is usually caused by Fe2+ but can also come from Cu2+ in rare Brazilian elbaites [spectrum, 7K].

Green color comes from Fe2+-Ti4+ IVCT together with Fe2+, or from Cr3+ or V3+ alone.

Amber to orange-brown colors (often seen in dravites) come from Fe2+-Ti4+ alone.

A greenish yellow color is from Mn2+ [Mn-elbaite spectrum 5K].

Pink and red colors are from Mn3+. The color of pink manganese-containing tourmalines often is associated with exposure to ionizing radiation (such as from the decay of 40K, a common  constituent of pegmatites).

Brown to orange-brown colors result from Mn2+-Ti4+ IVCT.

Black tourmalines (schorls (60 cm cluster, Czech Republic), etc.) are dark because of their high concentrations of iron, manganese and titanium. When they are ground very thin, they are usually blue or brownish-green [schorl spectrum, 6K].

Many tourmalines owe their color to a mixture of metal ions. The great diversity of color in tourmalines is due the the variability in which these mixtures occur. 

Images of Tourmaline Slices

For images of colorful tourmaline slices and more information about their color go to the section on tourmaline slices . 

Images of representative tourmaline spectra

Visible Spectra: polarizations: (a = incident light polarized perpendicular to c-axis; c = parallel to c-axis)

Blue, green, brown and black Fe-containing tourmalines

  • GRR 512 image, 6K; Schorl, GRR 512, White Queen Mine, Pala, California, 0.010 mm thick. Black in mass, blue when very thin. Contains 13.5% "FeO" and 0.95% "MnO". Data Files: a 0K; c 0K;
  • GRR 596 image, 6K; Elbaite, GRR 596G, Afghanistan, 0.25 mm thick. Dark green crystal colored by Fe2+ and Ti4+ - Fe2+ interactions. Contains 4.32% "FeO", 1.67% "MnO" and 0.04% "TiO2". Data Files: a 8K ; c 8K ;
  • GRR 787 image, 5K; Dravite, GRR 787, Sweeney Canyon, Anza Borrego, California, USA, 0.10 mm thick. The black crystal that most people would call schorl is green when thin. The intense absorptions in the perpendicular to c direction at 730 and 1120 nm result from enhancement of Fe2+ bands caused by interactions with Fe3+. The intense absorption in the same direction near 430 nm is from Fe2+ - Ti4+ intervalence charge transfer. The crystal contains 6.93% "FeO", 0.05% "MnO" and 0.53% "TiO2". Data Files: a 0K ; c 0K .
  • GRR 794 image, 5K; Foitite, GRR 794, Schindler Mine, California, USA, 0.048 mm thick. Black crystal, blue when thin. Data Files: a 22 K ; c 22 K .
  • S3 image, 4K, Dravite, S3, Newry, Maine, USA.  Brown to green, complexly zoned.  Spectra from a green zone.  Contains Mg1.19 Fe1.16 Ti 0.04. Data files:  a 0K ; c 0K .
  • CIT 12683 image, 5K, Dravite, CIT 12683, Yinnietharra, Australia. Brown crystal, 0.680 mm thick. The absorption band near 450 nm arising from Fe2+ - Ti4+ intervalence charge transfer is the primary cause of the color of this crystal. Data files:  a 67 K ; c 66 K .
  • GRR 2098 image; Uvite, GRR 2098, Wata Poore area, Konar Province, Afghanistan. 3.98 mm thick. Pale brown crystal. The color is dominated by the Fe2+ - Ti4+ intervalance charge transfer arising from the minor amounts of both Fe and Ti that are in this crystal. Data Files: a 0K ; c 0K .
  • S 8 image, 5K; Uvite, S 8, Pierrepont, New York, USA, NMNH 81511, 0.10 mm thick. Black crystal. Contains 8.23% "FeO" and 0.55% "TiO2". Data Files: a 0K ; c 0K . 
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    Pink and yellow-green Mn-containing tourmalines

  • GRR 1368 image 5K; dark pink elbaite from Otjimbinque, Namibia. The color is from Mn3+ and represents one of the deeper colored natural pink tourmalines.
  • GRR 565 image 5K; light pink elbaite from the Himalaya Mine, Mesa Grande, California. The color is natural color from Mn3+.
  • GRR 565 image 5K; dark pink elbaite from the Himalaya Mine, Mesa Grande, California. This sample has been irradiated with 60Co gamma rays to enhance its color. The color is from Mn3+ and represents a typical treated color for pink tourmalines.
  • GRR 876 image 5K; heavily irradiated pink elbaite from the Stewart Mine, Pala, California. Although the sample has been treated, the color is from Mn3+ and resembles the color of natural pink tourmaline.
  • GRR 757 image, 5K; Yellow-green elbaite, GRR 757, Zambia, 2.00 mm thick, with high Mn2+ content. Ref: Rossman & Mattson (1986) Amer. Mineral 71, 599-602. Data Files: a 0K ; c 0K ;
  • GRR 1932 image, 4K; rossmanite, GRR 1932, Rozná, Czech Republic, 2.976 mm thick. This is a light pink crystal of the type specimen. The color comes from the radiation-induced Mn3+ content. Here is the NIR OH region 4K; of the same crystal. Data Files: a 0K ; c 0K ;
  • Paraiba pink tourmaline. Elbaite, São José da Batalha, Paraíba, Brazil, 1.84 mm thick. Pink crystal colored by both Mn and Cu2+. Contributed data from M Taran, Kiev. Data Files: a 14K ; c 14K . 

    •   Other colored varieties and species of tourmalines