Toemaline
Tourmaline is a cyclosilicate mineral. Its hardness ranges from 7-7.5 on the Mohs scale, making it slightly softer than emerald. Tourmaline occurs in several varieties and colors:
Achroite: Almost colorless
Rubellite: Pink - Red
Dravite: Yellow-brown to dark brown
Verdelite: Green
Indigolite: Blue
Siberite: lilac red to violet blue
Schorl: Black
Sometimes two to three different colors occur in a single stone. A well-known example is "Watermelon": red with a green border.
The value of tourmaline varies significantly by type, size and color. the Paraiba, a blue and green type, from a very limited area in Brazil is more valuable than diamonds.
Most tourmalines are mined in Brazil. They are also mined in Africa and Asia.