| 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 |
| Streak | White |
| Diaphaneity | Transparent to opaque |
| Density | 2.9–3.2 |
| Optical properties | Uniaxial (-) |
| Refractive index | nω = 1.635–1.650, nε = 1.615–1.632 |
| Birefringence | δ = 0.020 |
| 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 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.