Tourmaline, one of the two birthstones for October, is a semi-precious stone best known for its incomparable array of beautiful colours.
Sometimes known as the ‘gemstone of the rainbow’, tourmaline fascinates jewellers and scientists alike - and it’s easy to see how it has become such a popular gemstone.
Tourmaline is found in just about any colour - and even, rarely, without colour. Because it features such a complex mineral group, the slightest difference in the make-up of a tourmaline stone can completely change its look. Most crystals will display a range of different colours, and the colour may be different or more or less intense depending on the angle from which you look at it. Crystals can be green at one end and pink at the other, or green on the outside and pink on the inside (known as a watermelon tourmaline).
The stones are also divided into ‘species’, with blue tourmalines known as 'indigolites', yellowish-brown to dark brown ones as 'dravites' and black ones as 'schorl', to name just a few.
Tourmaline measures between 7 and 7.5 on the Moh’s scale, making it a popular choice for jewelry but also a little vulnerable to knocks and scratches through everyday wear.
Tourmaline is mainly found in Brazil and Africa, but there have been some findings in the United States.
Old Egyptian legend explains tourmaline’s array of colours on the grounds that, on its long journey up from the centre of the Earth, it passed over a rainbow.
However, confusion has surrounded tourmaline for much of modern history. In the 1500s, a Spanish conquistador washed the dirt from a green tourmaline crystal found in Brazil, and confused the vibrant gem with emerald. His confusion lived on until scientists recognized tourmaline as its own distinct mineral species in the 1800s. Similarly, pink tourmalines in the Russian crown jewels were believed to have been mistaken for ruby for centuries.
Brightly colored Sri Lankan gem tourmalines were later brought to Europe in large quantities by the Dutch East India Company to satisfy a demand.
Folklore has spoken of the healing effects of tourmaline, which vary slightly depending on its colour.
Tourmaline’s value varies widely. The most common forms can be very affordable, while more exotic colors naturally fetch higher prices.
For example, the Watermelon Tourmaline, which is green on one side and red on the other, would be far more valuable than a Schorl, which is a common black tourmaline.
Like with most stones, more visible inclusions result in a lower price.
Heat treatment can enhance the color of tourmaline, for example turning greenish stones a deep green, and brownish stones a deep red. Light pink stones can also be made colorless through heating.
The color of the gemstone can also be changed by irradiation, but the enhancements are vulnerable to fading when exposed to heat or bright light.
Tourmaline’s complexities make it the most colorful of all gemstones, and as such is a versatile and exciting choice when it comes to jewelry.