Tourmaline semiprecious gemstone index and mineral information

Tourmaline is a group of aluminoborosilicates, notably elbaite, dravite, schorl, and uvite. They crystallize as characteristic long prisms of triangular cross-section. Tourmalites are found in granites, pegmatites and quartz veins, and as an accessory in schists and gneisses. The true name for most gem tourmaline is elbaite, named for its type locality.

Tourmaline was discovered on the island of Elba, off the west coast of Italy. The name derives from the Sinhalese term turmali given to colored mixed crystals on the island of Sri Lanka. The tourmaline group refers to a number of related species and varieties.

The following varieties are recognized in the trade, according to color:

Achroite: colorless or almost colorless, quite rare.

Dravite: yellow-brown to dark brown, sometimes used for stones not of the dravite species.

Indicolite or Indigolite: named after the color blue in all shades.

Rubellite: pink to red, sometimes with a violet tint; ruby color is the most valuable.

Schorl: black, very common; used for mourning jewelry. Its name derives from an old mining term, sometimes applied to tourmaline that is not actually schorl.

Siberite: named after finds in Urals, lilac to violet blue.

Verdelite: Name meaning “green stone”, green in all shades. Instead of variety names, color names are simply added to the word tourmaline; like yellow tourmaline, pink tourmaline.

Other varieties of tourmalines are: the bi-and tricolor tourmalines, which consist of two, three or more colors. The most well-known combination of colors is the watermelon tourmaline, in which the crystal has a pink center and a green rim, or rind, so that it looks like a watermelon in cross-section. The best pink and green watermelon crystals can be found in South Africa, East Africa and Brazil. The tourmalized quartz, which occur when black tourmaline needles form as an inclusion within clear quartz; and the tourmalines cat’s eye in which the cat’s eye effect occurs when the tourmaline has a large quantity of needles; and they are ordered in a parallel manner, and the base of the stone is oriented parallel to the needles; then the stone will take the cat’s-eye effect. It is called cat’s-eye tourmaline and is particularly strong in the pink and green colors.

Tourmaline is confused with many gemstones, due to the large variety of colors, especially amethyst, andalusite, chrysoberyl, citrine, demantoid, emerald, hiddenite, idocrase, kunzite, morganite, peridot, prasiolite, ruby, topaz, zircon, and glass imitations.

Mohs’ hardness: 7 – 7.5