The Tourmaline Group


Tourmaline Classification Scheme
(Species approved by the International Mineralogical Association)

 Adachite CaFe2+3Al6(Si5AlO18)(BO3)3(OH)3OH
 Bosiite NaFe3+3(Al4Mg2)(Si6O18)(BO3)3(OH)3OH
 Chromium-dravite  NaMg3Cr6(Si6O18)(BO3)3(OH)3OH
 Chromo-alumino-povondraite NaCr3[Al4Mg2](Si6O18)(BO3)3(OH)3O
 Darrellhenryite NaLiAl2Al6(Si6O18)(BO3)3(OH)3O
 Dravite  NaMg3Al6(Si6O18)(BO3)3(OH)3OH
 Elbaite   Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3OH
 Feruvite CaFe2+3[Al5Mg](Si6O18)(BO3)3(OH)3OH
 Fluor-buergerite NaFe3+3Al6(Si6O18)(BO3)3(O)3F
 Fluor-dravite NaMg3Al6(Si6O18)(BO3)3(OH)3F
 Fluor-elbaite Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F
 Fluor-liddicoatite Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3F
 Fluor-schorl NaFe2+3Al6(Si6O18)(BO3)3(OH)3F
 Fluor-tsilaisite NaMn2+3Al6(Si6O18)(BO3)3(OH)3F
 Fluor-uvite CaMg3(Al5Mg)Si6O18(BO3)3(OH)3F
 Foitite   [][Fe2+2Al]Al6(Si6O18)(BO3)3(OH)3OH
 Lucchesiite Ca(Fe2+)3Al6Si6O18(BO3)3(OH)3O
 Luinaite-(OH) (Na,[])(Fe2+Mg)3Al6(Si6O18)(BO3)3(OH)3(OH)
 Magnesio-foitite   [][Mg2Al]Al6(Si6O18)(BO3)3(OH)4
 Maruyamaite K(MgAl2)(Al5Mg)Si6O18(BO3)3(OH)3O
 Olenite  NaAl3Al6(Si6O18)BO3)3(O)3(OH) 
 Oxy-chromium-dravite NaCr3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O
 Oxy-dravite Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3O
 Oxy-schorl Na(Fe2+2Al)Al6(Si6O18)(BO3)3(OH)3O
 Oxy-vanadium-dravite NaV3(V4Mg2)(Si6O18)(BO3)3(OH)3O
 Povondraite   NaFe3+3[Fe3+4Mg2](Si6O18)(BO3)3(OH)3O
 Rossmanite  [](LiAl2)Al6(Si6O18)(BO3)3(OH)4
 Schorl  NaFe2+3Al6(Si6O18)(BO3)3(OH)4
 Tsilaisite NaMn2+3Al6(Si6O18)(BO3)3(OH)3OH
 Uvite  CaMg3[Al5Mg](Si6O18)(BO3)3(OH)3OH
 Vanadio-oxy-chromium-dravite NaV3[Cr4Mg2](Si6O18)(BO3)3(OH)3O
 Vanadio-oxy-dravite NaV3[Al4Mg2](Si6O18)(BO3)3(OH)3O

    [] 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.
[Blue iron-containing elbaite from Pakistan.] [The spectrum of blue copper-containing elbaite from Paraiba State, Brazil. 

Green color comes from either Fe2+-Ti4+ IVCT together with Fe2+, or from either Cr3+ or V3+ alone, or in combination.
[Uvite from the Mogok region of Myanmar containing mostly V and some Cr]

Amber to orange-brown colors (often seen in dravites) come from Fe2+-Ti4+ alone.
[Dravite from Yinietharra, Western Austrailia, dominated by color derived from the Fe2+-Ti4+ interaction.]

Yellow to yellow-brown colors result from Mn2+-Ti4+ IVCT.
[Elbaite from the Hyakule Mine, Nepal, displaying colors from interactions with titanium with Mn2+-Ti4+ IVCT and Fe2+-Ti4+ IVCT in different zones].

A greenish yellow to yellow color is from Mn2+ plus Mn2+-Ti4+  IVCT. 
[Faceted 'canary tourmaline' from Zambia].  [Mn-elbaite spectrum].

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).

Black tourmalines (schorls, 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. [60 cm cluster of schorl from the Czech Republic]. [schorl spectrum].

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.
[A slice of tourmaline from the Himalaya Mine, San Diego County, California, showing different colors from different causes]


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; 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; 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; 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; 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, 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, 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; 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
  • Elbaite; Usakos, Namibia, blue crystal. 3.641 mm thick. Data Files: a 20K ; c 20K .
  • Elbaite; Usakos, Namibia, green crystal, 3.654 mm thick. Data Files: a 20K ; c 20K .
  • Green V3+ and Cr3+ tourmalines

     Cu2+ colored tourmalines

  • R030 image; Elbaite, São José da Batalha, Paraíba, Brazil, 0.20 mm thick. Blue crystal colored by Cu2+. Ref: Rossman et al. (1991) Amer. Mineral 76, 1479-1484. Data Files: a 7K ; c 12K
  • Elbaite-MT image; Elbaite, São José da Batalha, Paraíba, Brazil, 1.84 mm thick. Pink crystal colored by both manganese and copper.  Data Files: a 14K ; c 14K Contributed data from Michael Taran, Kiev.
  • Pink and yellow-green Mn-containing tourmalines

  • GRR 1368 image; dark pink elbaite from Otjimbinque, Namibia. The color is from Mn3+ and represents one of the deeper colored natural pink tourmalines.
  • GRR 565 image; light pink elbaite from the Himalaya Mine, Mesa Grande, California. The color is natural color from Mn3+.
  • GRR 565 image; 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; 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; Yellow-green elbaite, GRR 757, Zambia, 2.00 mm thick, with high Mn2+ content and some Ti4+ that interacts with the Mn2+. Ref: Rossman & Mattson (1986) Amer. Mineral 71, 599-602. Data Files: a 0K ; c 0K ;
  • Elbaite; Usakos, Namibia, pale yellow crystal, 5.353 mm thick. Data Files: a 20K ; c 20K .
  • GRR 1932 image; 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 ;
  • Red tourmaline with Fe

    Orange tourmaline


    Tourmaline with the Usambara Effect