Elbaite, a

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

boro-

silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...

, with the chemical composition Na(Li_1.5Al_1.5)Al₆Si₆O₁₈(BO₃)₃(OH)₄, is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

species belonging to the six-member ring cyclosilicate

tourmaline Tourmaline ( ) is a crystalline silicate mineral, silicate mineral group in which boron is chemical compound, compounded with chemical element, elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a ...

group. Elbaite forms three series, with dravite, with fluor-liddicoatite, and with schorl. Due to these series, specimens with the ideal

endmember An endmember (also end-member or end member) in mineralogy is a mineral that is at the extreme end of a mineral series in terms of purity of its chemical composition. Minerals often can be described as solid solutions with varying compositions of ...

formula are not found occurring naturally. As a

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

, elbaite is a desirable member of the tourmaline group because of the variety and depth of its colours and quality of the crystals. Originally discovered on the island of

Elba Elba (, ; ) is a Mediterranean Sea, Mediterranean island in Tuscany, Italy, from the coastal town of Piombino on the Italian mainland, and the largest island of the Tuscan Archipelago. It is also part of the Arcipelago Toscano National Park, a ...

, Italy in 1913, it has since been found in many parts of the world. In 1994, a major locality was discovered in Canada, at O'Grady Lakes in the

Yukon Yukon () is a Provinces and territories of Canada, territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s we ...

. Elbaite forms in igneous and metamorphic rocks and veins in association with lepidolite,

microcline Microcline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during s ...

, and spodumene in granite pegmatites; with andalusite and

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

in schist; and with molybdenite and

cassiterite Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains ...

in massive hydrothermal replacement deposits. Elbaite is allochromatic, meaning trace amounts of impurities can tint crystals, and it can be strongly pleochroic. Every color of the rainbow may be represented by elbaite, some exhibiting multicolor zonation. Microscopic acicular inclusions in some elbaite crystals show the cat's eye effect in polished cabochons.

Elbaite varieties

* Colorless: achroite variety () * Red or pinkish-red: Rubellite variety (from ''

ruby Ruby is a pinkish-red-to-blood-red-colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapph ...

'') * Light blue to bluish green: Brazilian indicolite variety (from ''

indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...

'') * Green: Brazilian verdelite variety (from ''

emerald Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr., and Kammerling, Robert C. (1991). ''Gemology'', John Wiley & Sons, New York ...

'') * Watermelon tourmaline is a zoned variety with a reddish center surrounded by a green outer zone resembling

watermelon The watermelon (''Citrullus lanatus'') is a species of flowering plant in the family Cucurbitaceae, that has a large, edible fruit. It is a Glossary of botanical terms#scandent, scrambling and trailing vine-like plant, and is plant breeding ...

rind, evident in cross-sectional slices of prisms, often displaying curved sides. File:Tourmaline achroïte 1(Pakistan).jpg, Achroite File:Tourmaline-195614.jpg, Rubellite File:Tourmaline-Quartz-214670.jpg, Indicolite File:Turmalingruppe-Elbait-Verdelith - in Quarz aus Brasilien.JPG, Verdelite File:Elbait Turmalin DSC 5183.jpg, Watermelon tourmaline Elbaite at Peabody

References

{{Gemstone Sodium minerals Lithium minerals Cyclosilicates Trigonal minerals Minerals in space group 160 Gemstones Tourmalines

Elbaite varieties

See also

References