Another distinctive characteristic of tourmalines is their strong pleochroism, especially in the darker green and brown varieties, meaning that their colour varies depending on the angle it is observed from. This is a key consideration in the cutting process of such gems. The very best gem quality tourmalines have a vitreous lustre and a very good clarity.
This gemstone’s name comes from the Sinhalese word “Thoramalli” which is a name given to all the different coloured minerals found in Sri Lanka.
Myths surrounding this gem go back to ancient Egypt, where they believed that tourmalines passed a magnificent rainbow on their journey from the earth’s centre to the surface, granting this gemstone its vast variety of colours.
Tourmalines have one of the greatest range of colours in the crystal world and they even exist in bi- or tricolour (e.g. the so-called watermelon variety, a multi-coloured tourmaline variety featuring a pink centre surrounded by green, resembling the colours of a watermelon). Because of their availability in such a broad colour range, tourmalines were often confused with other gemstones.From colourless to black, tourmalines literally come in all colours, the most highly demanded include the blue variety Paraiba (link to site) and the pink to red variety, which is also referred to as “rubellite”.
Tourmaline is found in many areas around the world, today’s major gem quality tourmaline deposits are Sri Lanka, Brazil, throughout Africa, the United States, Mexico, Afghanistan and Pakistan. Different sources are known for the appearance of tourmaline in specific colours. Today’s largest mixed colours tourmaline deposit can probably be found in the Minas Gerais region in Brazil. Tourmalines often occur in large crystals due to their formation in pegmatites.
The most common treatment found in tourmalines, even though most tourmalines available in the trade are untreated, is irradiation. This treatment is generally applied to tourmalines to enhance their colour and to remove undesired hues.