THE TOURMALINES
Stones of the tourmaline group show any color you can imagine - and if you see your first clear "paraiba electric blue", youīll see a color you could not imagine before.
The name comes from the singhalesian term "toramolli" what means: something small out of the earth. Its also said that it was turamali, stone with many colors.
Hardness is 7-7,5 and sometimes the stones have an inner tension, so be careful when seeting.
To understand the chemical structure you have to read big books.
Most of the tourmalines have "pleochroism", this is a colorchange depending on the direction you look at the stone, itīs more or less strong from not visible to "uups". In attention to the crystal growing directions we made a cube which is yellow, green or brown, just depending on the direction you look through the stone.
Because of their pyro, respectively piezo-electrical effect they are also used for technical applications for example in aircraft engines.
From time to time there are news that synthetic tourmalines had been created, this is nothing new but in contrast to beryl or sapphire itīs not possible in gemstone quality.
There are catīs eye tourmalines with a more or less clear chatoyance, if someone offers you a star Tourmaline put it together in a box with the hardness 12 garnet. | 
