Elbaite

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Elbaite
Elbaite with albite - Sao Jose da Safira, Minas Gerais, Brazil.jpg
General
Category Cyclosilicate
Formula
(repeating unit)
Na(Li1.5Al1.5)Al6Si6O18(BO3)3(OH)4
IMA symbol Elb [1]
Strunz classification 9.CK.05
Crystal system Trigonal
Crystal class Ditrigonal pyramidal (3m)
H–M symbol: (3m)
Space group R3m
Identification
ColorGreen, red to pink, blue, orange, yellow, colorless, multicolored
Crystal habit Prismatic; striated
Cleavage Poor/indistinct on {1120} and {1011}
Fracture Sub-conchoidal
Mohs scale hardness7+12
Luster Vitreous
Streak White
Diaphaneity Transparent to opaque
Density 2.9–3.2
Optical propertiesUniaxial (−); moderate relief
Refractive index nω = 1.635–1.650, nε = 1.615–1.632
Birefringence δ = 0.020
Other characteristics piezoelectric and pyroelectric
References [2] [3]
Major varieties
Achroitecolorless
Indicoliteblue
Rubellitered to pink
Verdelitegreen

Elbaite, a sodium, lithium, aluminium boro-silicate, with the chemical composition Na(Li1.5Al1.5)Al6Si6O18(BO3)3(OH)4, [4] is a mineral species belonging to the six-member ring cyclosilicate tourmaline group.

Contents

Elbaite forms three series, with dravite, with fluor-liddicoatite, and with schorl. Due to these series, specimens with the ideal endmember formula are not found occurring naturally.

As a gemstone, 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, 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.

Elbaite forms in igneous and metamorphic rocks and veins in association with lepidolite, microcline, and spodumene in granite pegmatites; with andalusite and biotite in schist; and with molybdenite and cassiterite 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

Elbaite specimen at Yale's Peabody Museum of Natural History Elbaite at Peabody.jpg
Elbaite specimen at Yale's Peabody Museum of Natural History

See also

Related Research Articles

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<span class="mw-page-title-main">Spinel</span> Mineral or gemstone

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2
O
4
in the cubic crystal system. Its name comes from the Latin word spinella, a diminutive form of spine, in reference to its pointed crystals.

<span class="mw-page-title-main">Tourmaline</span> Cyclosilicate mineral group

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.

<span class="mw-page-title-main">Amphibole</span> Group of inosilicate minerals

Amphibole is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO
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<span class="mw-page-title-main">Pleochroism</span> Optical phenomenon

Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light.

<span class="mw-page-title-main">Lepidolite</span> Light micas with substantial lithium

Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.

<span class="mw-page-title-main">Petalite</span> Silicate mineral, used in ceramic glazing

Petalite, also known as castorite, is a lithium aluminum tektosilicate mineral LiAlSi4O10, crystallizing in the monoclinic system. Petalite occurs as colorless, pink, grey, yellow, yellow grey, to white tabular crystals and columnar masses. It occurs in lithium-bearing pegmatites with spodumene, lepidolite, and tourmaline. Petalite is an important ore of lithium, and is converted to spodumene and quartz by heating to ~500 °C and under 3 kbar of pressure in the presence of a dense hydrous alkali borosilicate fluid with a minor carbonate component. Petalite (and secondary spodumene formed from it) is lower in iron than primary spodumene, making it a more useful source of lithium in, e.g., the production of glass. The colorless varieties are often used as gemstones.

<span class="mw-page-title-main">Zincite</span>

Zincite is the mineral form of zinc oxide (ZnO). Its crystal form is rare in nature; a notable exception to this is at the Franklin and Sterling Hill Mines in New Jersey, an area also famed for its many fluorescent minerals. It has a hexagonal crystal structure and a color that depends on the presence of impurities. The zincite found at the Franklin Furnace is red-colored, mostly due to iron and manganese dopants, and associated with willemite and franklinite.

<span class="mw-page-title-main">Brazilianite</span> Yellow-green phosphate mineral

Brazilianite, whose name derives from its country of origin, Brazil, is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites.

<span class="mw-page-title-main">Scapolite</span> Group of rock-forming silicate minerals

The scapolites are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite and marialite. Silvialite (Ca,Na)4Al6Si6O24(SO4,CO3) is also a recognized member of the group.

<span class="mw-page-title-main">Scolecite</span>

Scolecite is a tectosilicate mineral belonging to the zeolite group; it is a hydrated calcium silicate, CaAl2Si3O10·3H2O. Only minor amounts of sodium and traces of potassium substitute for calcium. There is an absence of barium, strontium, iron and magnesium. Scolecite is isostructural (having the same structure) with the sodium-calcium zeolite mesolite and the sodium zeolite natrolite, but it does not form a continuous chemical series with either of them. It was described in 1813, and named from the Greek word, σκώληξ (sko-lecks) = "worm" because of its reaction to the blowpipe flame.

<span class="mw-page-title-main">Kornerupine</span>

Kornerupine (also called Prismatine) is a rare boro-silicate mineral with the chemical formula (Mg,Fe2+)4(Al,Fe3+)6(SiO4,BO4)5(O,OH)2. It crystallizes in the orthorhombic – dipyramidal crystal system as brown, green, yellow to colorless slender tourmaline like prisms or in massive fibrous forms. It has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.34. Its indices of refraction are nα=1.660 – 1.671, nβ=1.673 – 1.683 and nγ=1.674 – 1.684.

<span class="mw-page-title-main">Fluor-liddicoatite</span>

Fluor-liddicoatite is a rare member of the tourmaline group of minerals, elbaite subgroup, and the theoretical calcium endmember of the elbaite-fluor-liddicoatite series; the pure end-member has not yet been found in nature. Fluor-liddicoatite is indistinguishable from elbaite by X-ray diffraction techniques. It forms a series with elbaite and probably also with olenite. Liddiocoatite is currently a non-approved mineral name, but Aurisicchio et al. (1999) and Breaks et al. (2008) found OH-dominant species. Formulae are

<span class="mw-page-title-main">Fluorellestadite</span> Nesosilicate mineral

Fluorellestadite is a rare nesosilicate of calcium, with sulfate and fluorine, with the chemical formula Ca10(SiO4)3(SO4)3F2. It is a member of the apatite group, and forms a series with hydroxylellestadite.

<span class="mw-page-title-main">Serandite</span> Mineral

Serandite is a mineral with formula Na(Mn2+,Ca)2Si3O8(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.

<span class="mw-page-title-main">Tarbuttite</span> Phosphate mineral

Tarbuttite is a rare phosphate mineral with formula Zn2(PO4)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Coventry Tarbutt.

<span class="mw-page-title-main">Zigrasite</span>

Zigrasite is a phosphate mineral with the chemical formula of MgZr(PO4)2(H2O)4. Zigrasite was discovered and is only known to occur in the Dunton Quarry at Oxford County, Maine. Zigrasite was specifically found in the giant 1972 gem tourmaline-bearing pocket at the Dunton Quarry. Zigrasite is named after James Zigras who originally discovered and brought the mineral to attention.

<span class="mw-page-title-main">Phosphosiderite</span> Phosphate mineral

Phosphosiderite is a rare mineral named for its main components, phosphate and iron. The siderite at the end of phosphosiderite comes from the word "sideros", the Greek word for iron. It was published in 1890, and has been a valid species since pre-IMA. It is an IMA approved mineral which got grandfathered, meaning its name is still believed to refer to an existing species.

<span class="mw-page-title-main">Rubellite</span> Mineral

Rubellite is the red or pink variety of tourmaline and is a member of elbaite. Rubellite is also the rarest gem in its family. It is occasionally mistaken for ruby. These gems typically contain inclusions.

Tsilaisite is a manganese rich variety of elbaite tourmaline. It is also known as Tsilaizite. Tsilaisite is related Fluor-tsilaisite. The gem is named after the location it was first found.

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. Elbaite. Mindat
  3. Elbaite. Webmineral
  4. "IMA Mineral List with Database of Mineral Properties".