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Concept
Tourmaline
Summary
Tourmaline (ˈtʊərməlɪn,_-ˌliːn ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.
The name is derived from the Sinhalese (ටෝරමල්ලි), which refers to the carnelian gemstones.
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 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 of tourmaline include the following:
Schorl species
Brownish-black to black—
Dravite species (from the Drave district of Carinthia)
Dark yellow to brownish-black—
Elbaite species (named after the island of Elba, Italy)
Red or pinkish-red— variety
Light blue to bluish-green— variety (from indigo)
Green— or emerald variety
Colorless— variety ()
The most common species of tourmaline is , 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.
Official source
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Ontological neighbourhood