Tourmaline: Every Colour of the Rainbow
Tourmaline comes in more colours than almost any other gem, from rose pink and grass green to deep blue, and many stones show two at once.
Tourmaline is a complex boron silicate with a long list of possible ingredients. Small changes in chemistry give it an enormous range of colours: pink and red rubellite, green verdelite, blue indicolite, and bicoloured or watermelon stones that are pink in the centre and green at the rim. Our collection here is small, with each piece chosen one at a time.
Pakistan and Afghanistan are important sources. Pegmatite deposits in Gilgit-Baltistan and in neighbouring Nuristan have produced fine pink, green and bicolour crystals. Origin appears on a listing only when we can stand behind it.
Points to check
- Colour: pure, saturated tones bring the highest prices. Neon blue to green copper-bearing tourmaline, known as Paraíba type, is in a class of its own.
- Direction: tourmaline is strongly pleochroic, showing a darker colour down the length of the crystal. Good cutters orient it to show the best face.
- Clarity: green and blue stones are often clean, while pink and red usually contain inclusions, which are accepted.
Heating is used on some green and blue stones to lighten them, and some pink stones are irradiated. Treatment, where we know it, is stated on every listing.
In local tradition tourmaline is sometimes recommended in place of other stones, depending on its colour. It is also the October birthstone, and its variety of shades makes it easy to match to someone's favourite colour as a gift.
At 7 to 7.5 on the hardness scale, tourmaline is durable for daily rings. It can be brittle at sharp corners, so a bezel or protective claws suit pointed shapes. Clean it in warm soapy water and avoid ultrasonic cleaners for included stones.