The Tourmaline Group

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

    [] 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

 Cu²⁺ colored tourmalines

Pink and yellow-green Mn-containing tourmalines

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last updated: 18-Oct-2012