Renowned artists Paul Klee remarked, “Colour possesses me”. We believe in the same sentiment, especially if they are colours of a gemstone. Known for its dazzling hues, tourmaline was once believed to aid medical conditions. The unparalleled colour range of tourmaline makes it an ideal companion for designer gemstones and a substitute for the big three (ruby, emerald and sapphire). The ancient Egyptians believed that tourmalines travelled across a rainbow, and picked up all of its colours along the way.
In gemology, the distinction between gemstones is done through the order of groups, species and variety. Groups include closely related mineral species. The gems that have the same crystal structure but different chemical composition or vice versa, are put under one group. The group is then divided into species on the basis of chemical composition and structure. The species are then divided into varieties. Varieties are usually based on colour.
Types of Tourmaline
Tourmaline is a group. Tourmalines share the same chemical structure but different physical and chemical properties. The prominent tourmaline species are elbaite, dravite, schorl, liddiocatite and uvite.
Elbaites produce green, blue, yellow, red, colourless, pink and combination of colours. These are the most common tourmalines. Elbaites have the most of number of hues in it.
Liddicoatite produces striking colour zoned tourmalines. Often these tourmalines are parti-coloured. If both the colours are very prominent, then the gemstone is eligible to be called bi-coloured tourmaline. The watermelon tourmaline is another sought-after tourmaline that, as the name suggests, has the colours of watermelon present in it.
Schrol forms black coloured tourmaline. It is rarely used in jewellery but there have been instances where it has been found in mourning jewellery.
Dravite and uvite often showcase reddish brown and yellowish brown colours. Some tourmalines may also be a combination of dravite and uvite.
Often tourmalines of certain colours have trade names. For example, pink to rich deep red tourmalines are called rubellites. Green tourmalines are called as verdelite. Blue tourmalines are called as indicolite. Chrome tourmaline is the name given to strong green colour that can at times rival an emerald. Chrome tourmaline is believed to owe its colour to the element chromium.
Sources of Tourmaline
Brazil is a famous source of tourmalines. Africa too has a high production of tourmalines. These are found in Zambia, Nigeria, Madagascar, Kenya and Tanzania. Traditionally Brazil was famous (it still is) for its tourmalines and the rich colours it produced. However, tourmalines from Africa are not far behind.
Other sources of tourmalines include Pakistan, Afghanistan, Russia and The United States.
The largest producer in for gem quality tourmalines is Brazil’s Minas Gerais.
Paraiba Tourmalines display a rich colour of neon green and blue. Paraibas command the highest prices. This tourmaline comes from the area of Paraiba (after which it is named) in Brazil. The exotic colour is due to the presence of copper. The element copper is responsible for colour in other famous gemstones such as turquoise as well. However, what makes it rare is that in tourmalines, it is not often the case. Due to its striking colour, cutters often prioritize colour and not the size while making cutting decisions.
In recent years, Africa has also emerged as a source for commercial quality Paraiba. The trade name for it varies from “African Paraiba” to “Paraiba like”. However, it has to be noted that the Paraibas out of Africa are usually heat-treated and fail to achieve the intense colour produced by Brazil.
Cat’s Eye Tourmalines
Sometimes gemstones display unusual and beautiful effects due to inclusions in them or other chemical and physical properties. They are known to display a ‘phenomenon’. The case for a cat’e eye tourmaline remains the same. You might have seen gemstones that seem to display a cat’s eye effect as you tilt them. Hollow tubes cause cat’s eye effect in tourmalines.
Tourmalines that have the colours green and pink together are called watermelon tourmalines. The outer portion of the tourmaline is green while the inner portion is red, just like a watermelon. Often these are cut into slices and sold as they look very desirable and command higher prices.
Tourmalines can be heat-treated or put through irradiation. These treatments are done to enhance the colour or lighten it depending on the stone and its desired colour. The colour of the stone does not change but instead the intensity of it. Heat treatments are a very common practice for paraiba tourmalines as well as rubellites (pink and red tourmalines)
Irradiation is often practiced on tourmalines that are lighter in colour. Often the treatment goes undetected. However, the effect of irradiation can fade away with time.
Tourmalines can be fracture-filled too if they have the potential to command a high price. Sometimes, they are filled with epoxy resins and polymers. They might also be treated with acid to remove or lighten inclusions.
What we love about tourmalines is not only the vast range of colours it produces but also the intensity of each colour. The next time you are looking for a fine coloured gemstone, make sure you consider a tourmaline!