Elbaite (Tourmaline) Gem Guide and Properties Chart

The tourmaline family consists of at least 14 distinct minerals, but the elbaite variety accounts for nearly all gem-quality tourmaline. It was named for the colored and colorless tourmalines found on the picturesque island of Elba off the western coast of Italy. Although best known in shades of green and red, elbaite can also be blue, purple, yellow, or colorless. Notable varieties of elbaite include rubellite, green tourmaline, indicolite, watermelon tourmaline, and Paraiba tourmaline.

General Information

Classification
Optical Properties
Characteristic Physical Properties
Chemistry & Crystallography

Common Name

Elbaite

Species

Tourmaline

Transparency

Transparent - Translucent

Dispersion

Strength: Moderate Fire Value: 0.017

Refractive Index

1.614-1.666

Birefringence

0.018-0.020

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

Pleochroism

Dichroic, moderate to strong, varying shades of body color

Hardness

7-7.5

Streak

White

Specific Gravity

2.900-3.100

Toughness

Good

Inclusions

Green elbaite tourmaline stones are type I clarity stones. Blue, purple, orange, yellow and bi-color or parti-colored elbaite tourmalines are type II clarity stones. Stones might contain liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning.

Luster

Vitreous

Stability

Very Good

Fracture

Conchoidal, Subconchoidal, Uneven

Cleavage

Poor, in two directions

Chemical Name

Complex boro-silicate of Al, Li and Na

Chemical Formula

Na(Li₁.₅Al₁.₅)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)