Tourmaline

Tourmaline 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 , which refers to the carnelian gemstones.

History

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.

Species and varieties

Commonly encountered species and varieties of tourmaline include the following:

Schorl species
* Brownish-black to black—
Dravite species
* Dark yellow to brownish-black—
Elbaite species
* Red or pinkish-red— variety
* Light blue to bluish-green— variety
* Green— variety
* Colorless— variety
Schorl

The most common species of tourmaline is, the sodium iron 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 was then named "Schorl", 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 was written by Johannes Mathesius 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.

Dravite

, also called, is the sodium magnesium rich tourmaline endmember. Uvite, in comparison, is a calcium magnesium tourmaline. Dravite forms multiple series, with other tourmaline members, including schorl and elbaite.
The name dravite was used for the first time by Gustav Tschermak, Professor of Mineralogy and Petrography at the University of Vienna, in his book Lehrbuch der Mineralogie for magnesium-rich tourmaline from village Dobrova near Unterdrauburg in the Drava river area, Carinthia, Austro-Hungarian Empire. Today this tourmaline locality at Dobrova, is a part of the Republic of Slovenia. Tschermak gave this tourmaline the name dravite, for the Drava river area, which is the district along the Drava River in Austria and Slovenia. The chemical composition which was given by Tschermak in 1884 for this dravite approximately corresponds to the formula, which is in good agreement with the endmember formula of dravite as known today.
Dravite varieties include the deep green chromium dravite and the vanadium dravite.

Elbaite

A lithium-tourmaline elbaite was one of three pegmatitic minerals from Utö, Sweden, in which the new alkali element lithium was determined in 1818 by Johan August Arfwedson for the first time. Elba Island, Italy, was one of the first localities where colored and colorless Li-tourmalines were extensively chemically analysed. In 1850, Karl Friedrich August Rammelsberg described fluorine in tourmaline for the first time. In 1870, he proved that all varieties of tourmaline contain chemically bound water. In 1889, Scharitzer proposed the substitution of by F in red Li-tourmaline from Sušice, Czech Republic. In 1914, Vladimir Vernadsky proposed the name Elbait for lithium-, sodium-, and aluminum-rich tourmaline from Elba Island, Italy, with the simplified formula. Most likely the type material for elbaite was found at Fonte del Prete, San Piero in Campo, Campo nell'Elba, Elba Island, Province of Livorno, Tuscany, Italy. In 1933 Winchell published an updated formula for elbaite,, which is commonly used to date written as. 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.

Chemical composition

The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. Its composition varies widely because of isomorphous replacement, and its general formula can be written as, where:

X = Ca, Na, K, ▢ = vacancy
Y = Li, Mg, Fe²⁺, Mn²⁺, Zn, Al, Cr³⁺, V³⁺, Fe³⁺, Ti⁴⁺, ▢ = vacancy
Z = Mg, Al, Fe³⁺, Cr³⁺, V³⁺
T = Si, Al, B
B = B, ▢ = vacancy
V = OH, O
W = OH, F, O

Species Name	Ideal Endmember Formula	IMA Number	Symbol
Adachiite	CaFe²⁺₃Al₆₃₃OH	2012-101	Adc
Alumino-oxy-rossmanite	▢Al₃Al₆₃₃O	2020-008	Aorsm
Bosiite	NaFe³⁺₃Si₆O₁₈₃₃O	2014-094	Bos
Celleriite	▢Al₆₃₃	2019-089	Cll
Chromium-dravite	NaMg₃Cr₆Si₆O₁₈₃₃OH	1982-055	Cdrv
Chromo-alumino-povondraite	NaCr₃Si₆O₁₈₃₃O	2013-089	Capov
Darrellhenryite	NaLiAl₂Al₆Si₆O₁₈₃₃O	2012-026	Dhry
Dravite	NaMg₃Al₆Si₆O₁₈₃₃OH	- 1884 -	Drv
Dutrowite	NaAl₆Si₆O₁₈₃₃O	2019-082	Dtw
Elbaite	NaAl₆Si₆O₁₈₃₃OH	- 1913 -	Elb
Ertlite	NaAl₃Al₆₃₃O	2023-086	Etl
Ferro-bosiite	NaFe³⁺₃Si₆O₁₈₃₃O	2022-069	Fbos
Feruvite	CaFe²⁺₃Si₆O₁₈₃₃OH	1987-057	Fer
Fluor-buergerite	NaFe³⁺₃Al₆Si₆O₁₈₃O₃F	1965-005	Fbu
Fluor-dravite	NaMg₃Al₆Si₆O₁₈₃₃F	2009-089	Fdrv
Fluor-elbaite	NaAl₆Si₆O₁₈₃₃F	2011-071	Felb
Fluor-liddicoatite	CaAl₆Si₆O₁₈₃₃F	1976-041	Fld
Fluor-rossmanite	▢Al₆Si₆O₁₈₃₃F	2023-111	Frsm
Fluor-schorl	NaFe²⁺₃Al₆Si₆O₁₈₃₃F	2010-067	Fsrl
Fluor-tsilaisite	NaMn²⁺₃Al₆Si₆O₁₈₃₃F	2012-044	Ftl
Fluor-uvite	CaMg₃Si₆O₁₈₃₃F	- 1930 -	Fluvt
Foitite	▢Al₆Si₆O₁₈₃₃OH	1992-034	Foi
Liddicoatite	CaAl₆Si₆O₁₈₃₃	2025-047	Ld
Lucchesiite	Ca₃Al₆Si₆O₁₈₃₃O	2015-043	Lcc
Magnesio-dutrowite	NaAl₆Si₆O₁₈₃₃O	2023-015	Mdtw
Magnesio-foitite	▢Al₆Si₆O₁₈₃₃OH	1998-037	Mfoi
Magnesio-lucchesite	Ca₃₃O	2019-025	Mlcc
Maruyamaite	KSi₆O₁₈₃₃O	2013-123	Mry
Olenite	NaAl₃Al₆Si₆O₁₈₃O₃OH	1985-006	Ole
Oxy-chromium-dravite	NaCr₃Si₆O₁₈₃₃O	2011-097	Ocdrv
Oxy-dravite	NaSi₆O₁₈₃₃O	2012-004	Odrv
Oxy-foitite	▢Al₆Si₆O₁₈₃₃O	2016-069	Ofoi
Oxy-schorl	NaAl₆Si₆O₁₈₃₃O	2011-011	Osrl
Oxy-vanadium-dravite	NaV₃Si₆O₁₈₃₃O	1999-050	Ovdrv
Povondraite	NaFe³⁺₃Si₆O₁₈₃₃O	1979	Pov
Princivalleite	NaAl₆Si₆O₁₈₃₃O	2020-056	Pva
Rossmanite	▢Al₆Si₆O₁₈₃₃OH	1996-018	Rsm
Schorl	NaFe²⁺₃Al₆Si₆O₁₈₃₃OH	- 1505 -	Srl
Tsilaisite	NaMn²⁺₃Al₆Si₆O₁₈₃₃OH	2011-047	Tsl
Uvite	CaMg₃Si₆O₁₈₃₃OH	2000-030	Uvt
Vanadio-oxy-chromium-dravite	NaV₃Si₆O₁₈₃₃O	2012-034	Vocdrv
Vanadio-oxy-dravite	NaV₃Si₆O₁₈₃₃O	2012-074	Vodrv

Mineral species that were named before the IMA was founded in 1958 do not have an IMA number.
The IMA commission on new mineral names published a list of approved symbols for each mineral species in 2021.
A revised nomenclature for the tourmaline group was published in 2011.