Tourmaline: buying guide to the Rainbow Gemstone

Tourmaline is not really just one gemstone. Tourmaline is actually several different, but closely related minerals, members of what is called The Tourmaline Group. These gems come in rich and vivid colors and are often a mixture of more then one color. Black opaque tourmalines can Sparkle nicely and produce sharp crystal forms. Tourmalines can be cut as precious gems, carved into figurines, cut as cabochons, sliced into cross-sections and natural specimens are enthusiastically added to many a rock hound’s collection.

Members of The Tourmaline Group are:

•Buergerite (Sodium Iron Aluminum Boro-silicate Hydroxide Fluoride)
•Chromdravite (Sodium Magnesium Chromium Iron Aluminum Boro-silicate Hydroxide Fluoride)
•Dravite (Sodium Magnesium Aluminum Boro-silicate Hydroxide)
•Elbaite (Sodium Lithium Aluminum Boro-silicate Hydroxide)
•Feruvite (Calcium Iron Magnesium Aluminum Boro-silicate Hydroxide)
•Foitite (Iron Aluminum Boro-silicate Hydroxide)
•Liddicoatite (Sodium Lithium Aluminum Boro-silicate Oxide Hydroxidem Fluoride)
•Olenite (Sodium Aluminum Boro-silicate Oxide Hydroxide)
•Povondravite (Sodium Iron Boro-silicate Hydroxide Oxide)
•Schorl (Sodium Iron Aluminum Boro-silicate Hydroxide)
•Uvite (Calcium Sodium Magnesium Iron Aluminum Boro-silicate Hydroxide Fluoride)

Tourmalines have many unique properties not found in other gems.

First, they are piezoelectric. This means that when a crystal is heated, compressed or vibrated a different electrical charge will form at opposite ends of the crystal one end being positive and the other being negative. Tourmaline crystals will also vibrate when an electrical currant is applied.

Secondly Tourmalines are pleochroic. This means that the crystal will look darker in color when viewed down the long axis of the crystal than when viewed from the side. Gem cutter will often use this to their advantage cutting gems to enhance this quality.

Specific color group names for Tourmaline:

- Dravite subgroup: Brown – dravite (from the Drave district of Carinthia)
- Schorl subgroup: Black – schorl
- Elbaite subgroup: named after the island of Elba, Italy
- Rose or pink – rubellite (from ruby)
- Dark blue – indicolite (from indigo)
- Light blue – Brazilian sapphire
- Green – verdelite or Brazilian emerald
- Colorless – achroite (from the Greek for “colorless”)

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