Elbaite

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Elbaite
General
Category	Silicate mineral
Chemical formula	Na(LiAl)3Al6Si6O18(BO3)3(OH)4
Identification
Color	Green, red to pink, blue, orange, yellow, colorless, multicolored
Crystal habit	Prismatic; striated
Crystal system	Trigonal
Cleavage	Poor/Indistinct on {1120} and {1011}
Fracture	Sub Conchoidal
Mohs Scale hardness	7½
Luster	Vitreous
Refractive index	nω = 1.635 - 1.650 nε = 1.615 - 1.632
Optical Properties	Uniaxial (-)
Birefringence	δ = 0.020
Streak	White
Density	2.9 - 3.2
Diaphaneity	Transparent to opaque
References	[1][2]
Major varieties
Achroite	colorless
Indicolite	blue
Rubellite	red to pink
Verdelite	green

Elbaite, a sodium, lithium, aluminium boro-silicate, is a mineral species belonging to the tourmaline group. Elbaite forms three series, with dravite, with liddicoatite, and with schorl. Due to these series specimens with the ideal end-member formula are not found occurring natually.

As a gemstone, elbaite is reckoned to be one of the most desirable 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.

[edit] References