About
Tourmaline is extremely popular among collectors and is a well-known gemstone. It is the most multicolored mineral type known, occurring in virtually every color of the spectrum. Individual stones are often multicolored and are unsurpassed in their beauty.
The color of some Tourmaline can be enhanced through heat treatment. Some greenish stones can be made deep green, some brownish-red stones can be made red, and some light pink stones can be made colorless through heating.
Tourmaline has many interesting optical properties. Many green and blue specimens are strongly pleochroic. When viewed through their vertical axis, such specimens appear darker in color than when seen through their horizontal axis. In other Tourmalines, the color may actually be different when viewed at different angles because of the pleochroism. Certain Tourmalines exhibit a cat's eye effect when polished into cabochons.
Tourmaline is both pyroelectric and piezoelectric. If a specimen is put under a pressure or temperature change, it will generate an electrical charge. When this happens, dust particles become attached to the crystal ends.
For additional information, see the gemstone section on Tourmaline.
Crystal Forms & Aggregates
Other ID Marks
2) Piezoelectric.
3) A few forms of Tourmaline fluoresce yellow in shortwave ultraviolet light.
Striking Features
Environment
Varieties
✓ common · ✗ uncommon
- {%Buergerite%}— Rare individual member mineral of the Tourmaline group, occurring almost exclusively at Mexquitic, San Luis Potosí, Mexico.
- {%Dravite%}— Individual member mineral of the Tourmaline group. It is usually brown in color, and the term may be corrupted to include all forms of brown Tourmaline.
- {%Elbaite%}— The most well-known individual member mineral of the Tourmaline group. Elbaite is the most transparent and colorful form of Tourmaline. The term Elbaite may be corrupted in the gemstone industry to refer specifically to green Tourmaline.
- {%Liddicoatite%}— Uncommon member mineral of the Tourmaline group found primarily in Madagascar. It is the calcium analogue of Elbaite, containing calcium in its chemical formula instead of sodium.
- {%Schorl%}— Individual member mineral of the Tourmaline group. It is black in color, and the term may be corrupted to include any very dark Tourmaline forms.
- {%Uvite%}— Uncommon member mineral of the Tourmaline group, usually found in metamorphic environments such as marbles.
- Achroite— Colorless variety of Elbaite Tourmaline.
- Indicolite— Blue variety of Elbaite Tourmaline.
- Rubellite— Pink to red variety of Elbaite Tourmaline.
- Watermelon Tourmaline— Variety of Elbaite Tourmaline that is green on the outside and red on the inside.
Uses
Tourmaline can form in extremely aesthetic slender crystals that are highly valued by collectors. It is one of the most prized minerals, and fine crystals can be among the most beautiful examples in the mineral kingdom. Instead of being faceted, many fine Tourmaline crystals are preserved for their beauty. Thick, elongated crystals are sometimes sliced into sections and sold as "Tourmaline cross sections".
The piezoelectric nature of Tourmaline makes it useful as a component of high pressure gauges.
Noteworthy Localities
Elbaite | Schorl | Dravite | Uvite | Liddicoatite | Buergerite
Common Mineral Associations
Distinguishing Similar Minerals
Apatite - Crystals lack striations , softer (5).
Epidote - Softer, different crystal habits.
Photos
See all 13 photos →Crystal forms
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