Navette-cut diamonds around a tourmaline, which is how the stone is usually presented: as the colour in a piece built of white. Navette Cut Diamond and Tourmaline Cocktail Ring, 14K gold
Tourmaline is the most chromatically promiscuous gem there is. It occurs in pink, red, green, blue, yellow, brown, black, colourless, and in single crystals that change colour halfway along their length. For most of history that variety worked against it, because a stone that could be any colour was repeatedly mistaken for something else: the Russian crown jewels included a famous ruby that turned out to be a red tourmaline, and Brazilian emeralds sent to Europe in the sixteenth century were frequently green tourmaline instead.
The varieties worth knowing
| Name | Colour | Note |
|---|---|---|
| Rubellite | Pink to red | The most valuable of the traditional colours |
| Indicolite | Blue to blue-green | Scarce, and darker stones are commoner than bright |
| Verdelite | Green | The everyday green tourmaline |
| Watermelon | Pink core, green rim | Sliced across the crystal to show both |
| Paraiba | Electric neon blue-green | Copper-bearing, found in Brazil in the 1980s, extremely expensive |
| Schorl | Black | Common, used in Victorian mourning jewelry |
Paraiba deserves its own sentence, because it is the reason tourmaline appears in headlines. Discovered in the Brazilian state of Paraiba in 1989, it glows in a way no other stone does, and fine examples trade above most diamonds by weight. Material from Mozambique and Nigeria with similar chemistry is also sold as Paraiba, at lower prices, and the distinction is worth asking about above a certain sum.
Where it turns up in antique jewelry
Tourmaline appears throughout the nineteenth and twentieth centuries, usually as the coloured element in a piece whose structure is diamonds or gold. Green and pink tourmaline suited the naturalistic Victorian taste; the Edwardians used it in pastel combinations; the 1940s and 1950s used large tourmalines in cocktail rings, where the stone's size and colour did the work. Because it was never as fashionable as ruby, sapphire or emerald, it is consistently better value in antique settings than those three, which is exactly why I keep buying it.
Tourmaline sharing a 1920s cluster with diamond and ruby, and holding its own against both. Antique Cluster Ring, Tourmaline, Diamond and Ruby, platinum and 18K gold, 1920s
How to recognise it
Tourmaline is strongly pleochroic, which means it shows different colours when viewed from different directions, and the effect is often visible by simply turning the stone. It is usually noticeably darker down the length of the crystal than across it, which is why cutters orient stones to avoid a dark, closed appearance. If a tourmaline looks black from one angle and lively from another, that is the stone behaving normally rather than a fault.
It sits at 7 to 7.5 on the hardness scale, similar to quartz, so it is entirely wearable but will scratch against sapphire, ruby and diamond in a jewelry box. Long thin inclusions running parallel to the crystal are typical and not a defect.
Buying sensibly
Colour is everything. Bright, open colour costs many times what dark, closed colour does at the same weight, and photographs flatter dark stones badly. Ask for a picture in daylight, not under a lamp.
Assume treatment. Heating to improve colour is routine and stable. Irradiation is also used, particularly on pink material, and is generally undetectable and permanent. On an antique piece this is not worth agonising over, for the same reasons set out in the wider discussion of period stone treatments.
Watch for names. Rubellite, indicolite and Paraiba are trade names that carry price premiums, and the boundaries between them are matters of opinion. A stone described as rubellite that looks pink rather than red is being helped along by its label.
Care
Warm soapy water and a soft brush. Avoid ultrasonic cleaners, since tourmaline frequently contains liquid inclusions and internal fractures that vibration can propagate, and avoid steam and sudden temperature changes for the same reason. Store separately from harder stones. The general rules in the cleaning guide apply, with the ultrasonic warning underlined.
Frequently asked questions
What colour is tourmaline?
Any of them. It occurs in pink, red, green, blue, yellow, brown, black and colourless, and single crystals can show two colours at once.
What is watermelon tourmaline?
A crystal with a pink core and a green outer layer, usually cut in slices across the crystal so both colours show at once.
Is tourmaline valuable?
It ranges enormously. Ordinary green and brown material is inexpensive; fine rubellite and indicolite are serious stones; Paraiba tourmaline trades above most diamonds by weight.
Is tourmaline hard enough for a ring?
Yes, at 7 to 7.5 on the hardness scale it is similar to quartz. It will scratch against sapphire and diamond, so store it separately.
Why does my tourmaline look black from one angle?
Strong pleochroism. Tourmaline shows different colours along different crystal directions, and it is typically darkest down the length of the crystal.
Is tourmaline treated?
Commonly. Heating is routine and stable, and irradiation is used on some pink material. Both are permanent and generally undetectable without a laboratory.
How should I clean tourmaline?
Warm soapy water and a soft brush only. Ultrasonic cleaners and steam risk propagating the internal fractures the stone often contains.
Read next: What is a cocktail ring? · Emeralds in antique jewelry · Garnet vs ruby
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