Tourmaline has hardness of 7 - 7.5 Mohs. It is formed of complex aluminum borosilicate (Elbaite, Dravite, Uvite) and its specific gravity is 3.03 - 3.25.
Tourmalines are precious stones displaying a unique splendour of colours. According to an ancient Egyptian legend this is the result of the fact that on the long way from the Earths heart up towards the sun, Tourmaline travelled along a rainbow. And on its way it collected all the colours of the rainbow. This is why nowadays it is called the "Rainbow gemstone".
They offer a wide variety of choice for the discerning gemstones Jewellery enthusiast. A complete collection of all the colors represents a fascinating quest for the knowledgeable seeker of natures bounty. Dark blue, blue-green and green Tourmalines are often heated to lighten their colors. Red Tourmalines (also known as Rubelite) and pink varieties are often heated to lighten their colors. Red tourmalines (also known as Rubelite) and pink varieties are often heated and/or irradiated to improve their colors. Heat and irradiation color enhancement of Tourmalines are permanent.
Occasionally, some Tourmalines may have surface breaking fissures that the filled with resins and/or hardeners. Care must be observed with these gems. Avoid exposing them to harsh abrasives and strong chemical solvents.
The following varieties of gemstones come under it -
Brazilian emerald: Green
Indicolite: Dark blue
Rubellite: Pink to red