Tourmaline ( /ˈtʊərməlɪn/, -/iːn/ TOOR-mə-lin, -⁠leen) is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gemstone can be found in a wide variety of colors.

According to the Madras Tamil Lexicon the name comes from the word "thoramalli" (තෝරමල්ලි) or "tōra- molli", which is applied to a group of gemstones found in the southern parts of the Indian Subcontinent. According to the same source, the Tamil "tuvara-malli" (துவரைமல்லி) and "toramalli" are also derived from the Sinhalese root word. This etymology is also given in other standard dictionaries including the Oxford English Dictionary.

Brightly colored Ceylonese gem tourmalines were brought to Europe in great quantities by the Dutch East India Company to satisfy a demand for curiosities and gems. Tourmaline was sometimes called the "Ceylonese Sri Lankan Magnet" because it could attract and then repel hot ashes due to its pyroelectric properties.

Tourmalines were used by chemists in the 19th century to polarize light by shining rays onto a cut and polished surface of the gem. Commonly encountered species and varieties: Schorl species: Brownish black to black—schorl, Dravite species: from the Drave district of Carinthia

Dark yellow to brownish black—dravite, Elbaite species: named after the island of Elba, Italy

Red or pinkish-red—rubellite variety, Light blue to bluish green—Brazilian indicolite variety (from indigo), Green—verdelite or Brazilian emerald variety, Colorless—achroite variety (from the Greek "άχρωμος" meaning "colorless").

The most common species of tourmaline is schorl, the sodium iron (divalent) endmember of the group. It may account for 95% or more of all tourmaline in nature. The early history of the mineral schorl shows that the name "schorl" was in use prior to 1400 because a village known today as Zschorlau (in Saxony, Germany) was then named "Schorl" (or minor variants of this name), and the village had a nearby tin mine where, in addition to cassiterite, black tourmaline was found. The first description of schorl with the name "schürl" and its occurrence (various tin mines in the Ore Mountains) was written by Johannes Mathesius (1504–1565) in 1562 under the title "Sarepta oder Bergpostill". Up to about 1600, additional names used in the German language were "Schurel", "Schörle", and "Schurl". Beginning in the 18th century, the name Schörl was mainly used in the German-speaking area. In English, the names shorl and shirl were used in the 18th century. In the 19th century the names common schorl, schörl, schorl and iron tourmaline were the English words used for this mineral.

Tourmaline has a variety of colors. Iron-rich tourmalines are usually black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Rarely, it is colorless. Bi-colored and multicolored crystals are common, reflecting variations of fluid chemistry during crystallization. Crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called watermelon tourmaline. Some forms of tourmaline are dichroic; they change color when viewed from different directions.

Two dark-green rectangular tourmaline stones and one oval tourmaline stone. The pink color of tourmalines from many localities is the result of prolonged natural irradiation. During their growth, these tourmaline crystals incorporated Mn2+ and were initially very pale. Due to natural gamma ray exposure from radioactive decay of 40K in their granitic environment, gradual formation of Mn3+ ions occurs, which is responsible for the deepening of the pink to red color.

Varieties:

Achroite - A colourless variety of Tourmaline

Cat's Eye Tourmaline

Chrome-Tourmaline - An emerald-green variety of tourmaline.

Dravite - A sodium magnesium aluminium tourmaline species.

Elbaite - A sodium lithium aluminium tourmaline species.

Cuprian Elbaite - A copper-bearing Elbaite.

Paraíba Tourmaline

Fluor-uvite-Uvite Series - A calcium magnesium aluminium tourmaline species.

Indicolite - A blue gemmy variety of tourmaline (usually elbaite).

Liddicoatite - A calcium lithium tourmaline species.

Rubellite - A pink to red gem variety of tourmaline.

Schorl - A sodium iron aluminium tourmaline species.

Verdelite - A green gem variety of tourmaline

Watermelon Tourmaline - A variety of Tourmaline with colour zoning showing a pink core and green edges.