INDICOLITE, the blue variety of elbaite (tourmaline)

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VARIETY INFORMATION:

• VARIETY OF: Elbaite , (a Tourmaline ), Na(Li,Al)₃Al₆Si₆O₁₈(BO₃)₃ (OH)₄, Sodium Lithium Aluminum Boro-Silicate Hydroxide
• USES: Gemstone.
• BIRTHSTONE FOR: October
• COLOR: shades of blue
• INDEX OF REFRACTION: 1.62 and 1.68
• BIREFRINGENCE: 0.014 - 0.022
• HARDNESS: 7 - 7.5
• CLEAVAGE: absent
• CRYSTAL SYSTEM: trigonal
• PLEOCHROIC: strongly
• Specimens

Indicolite is the blue color variety of the tourmaline mineral elbaite. Its typical color is a deeper - almost neon - blue than other blue gems such as aquamarine and blue topaz. Indicolite is one of the rarer varieties of elbaite. Other varieties include a cat's eye variety, verdellite (green), rubellite (pink to red) and watermelon tourmaline (green outside and a red center). All elbaite specimens are strongly pleochroic meaning that they show stronger or even different colors when viewed from different angles. In indicolite, this causes the blue color to appear darker when viewed down the long axis of an uncut crystal. The gem cutter must be aware of this pleochroisim in order to maximize the color potential of the stone.