Tourmaline

Tourmaline or "tourmaline group" does not refer to a specific mineral, but to a group of minerals which share the same basic ring-shaped arrangements of silicon, boron and oxygen atoms.

Tourmaline is used commonly for a family of 11 minerals which share this structural arrangement. The name tourmaline comes from the word "turmali" used by Sri Lankan gem merchants to describe an undetermined mix of gemstones. These gemstones are commonly found in pegmatites where the conditions exist for the growth of spectacular crystals. These are some examples of the tourmaline family:

Schorl

Elbaite

Dravite

Uvite

Schorl is the most common of the tourmaline minerals, and may account for 95% of the tourmaline (wiki). Most of the gems are classified as varieties of elbaite.

Mindat: Tourmaline