Tourmaline (/ˈtʊərməlɪn, -ˌliːn/ TOOR-mə-lin, -⁠leen) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium.

Tourmaline was sometimes called the "Ceylonese Magnet" because it could attract and then repel hot ashes due to its pyroelectric properties.

[5] Tourmalines were used by chemists in the 19th century to polarize light by shining rays onto a cut and polished surface of the gem.

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".

[8] The name dravite was used for the first time by Gustav Tschermak (1836–1927), Professor of Mineralogy and Petrography at the University of Vienna, in his book Lehrbuch der Mineralogie (published in 1884) for magnesium-rich (and sodium-rich) tourmaline from village Dobrova near Unterdrauburg in the Drava river area, Carinthia, Austro-Hungarian Empire.

[10] A lithium-tourmaline elbaite was one of three pegmatitic minerals from Utö, Sweden, in which the new alkali element lithium (Li) was determined in 1818 by Johan August Arfwedson for the first time.

In 1914, Vladimir Vernadsky proposed the name Elbait for lithium-, sodium-, and aluminum-rich tourmaline from Elba Island, Italy, with the simplified formula (Li,Na)HAl6B2Si4O21.

[11] The first crystal structure determination of a Li-rich tourmaline was published in 1972 by Donnay and Barton, performed on a pink elbaite from San Diego County, California, United States.

It occurs as long, slender to thick prismatic and columnar crystals that are usually triangular in cross-section, often with curved striated faces.

Small slender prismatic crystals are common in a fine-grained granite called aplite, often forming radial daisy-like patterns.

[citation needed] A crystal of tourmaline is built up of units consisting of a six-member silica ring that binds above to a large cation, such as sodium.

The ring binds below to a layer of metal ions and hydroxyls or halogens, which structurally resembles a fragment of kaolin.

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.

Tourmaline is a durable mineral and can be found in minor amounts as grains in sandstone and conglomerate, and is part of the ZTR index for highly weathered sediments.

[24] Gem and specimen tourmaline is mined chiefly in Brazil and many parts of Africa, including Tanzania, Nigeria, Kenya, Madagascar, Mozambique, Malawi, and Namibia.

It is also mined in Asia, notably in Pakistan, Afghanistan, and Indonesia as well as in Sri Lanka and India,[25] where some placer material suitable for gem use is found.

The Empress Dowager Cixi of China loved pink tourmaline and bought large quantities for gemstones and carvings from the then new Himalaya Mine, located in San Diego County, California.

The first documented case was in 1890 when Charles Russel Orcutt found pink tourmaline at what later became the Stewart Mine at Pala, California in San Diego County.

Much of the paraiba tourmaline from Brazil does not actually come from Paraíba, but the neighboring state of Rio Grande do Norte.

A more recent African discovery from Mozambique has also produced tourmaline colored by copper, similar to the Brazilian paraiba.

Of the standard elbaite colors, blue indicolite gems are typically the most valuable,[32] followed by green verdelite and pink to red rubellite.