October Birthstone – Tourmaline
October’s other birthstone is Tourmaline. This is one of my favourite stones as it comes in such a variety of colours.
The name “tourmaline” comes from the Sinhalese words tura mali, which mean “stone of mixed colors.” As its name implies, tourmaline stands apart from other gems with its broad spectrum of colors in every shade of the rainbow. Ancient magicians used black tourmaline as a talisman to protect against negative energy and evil forces. Today, many still believe that it can shield against radiation, pollutants, toxins and negative thoughts.
Tourmaline is not one mineral, but a fairly complex group of minerals with different chemical compositions and physical properties. Certain trace elements produce distinct colors, and many resulting varieties have their own names:
Schrol or Black tourmaline – is rich in iron, which causes dark shades from deep brown to bluish-black. This variety makes up 95 percent of all tourmaline, though most of it isn’t gem-quality. Schorl, in particular, is said to have protective powers against harmful radiation, toxins and anxiety.
Dravite or brown tourmaline – is rich in magnesium, which causes colors ranging from brown to yellow. It’s named for the Drave District of Carinthina (now Slovenia) where it’s found.
Rubellite or red tourmaline – is caused by manganese; but if the colour becomes less vibrant under different light sources, it may be called pink tourmaline.
Indicolite or blue tourmaline can appear purplish blue or bluish green, depending on the amount of iron and titanium.
Verdelite or green tourmaline can resemble emerald, but if its colour is caused by chrome and vanadium, it’s called a chrome tourmaline.
Paraíba tourmaline is a vividly coloured purplish or greenish blue variety found in Paraíba, Brazil. It’s the most recently discovered, and because of its desirably intense colours, it’s one of the most valuable.
Parti-coloured tourmaline displays more than one colour, due to chemical fluctuations during crystallisation. A common colour combination is green and pink. These are often cut in slices to reveal a red enter surrounded by a green rim, earning the name “watermelon tourmaline.”
Egyptian legend tells that tourmaline found its famed array of colours when, on its journey up from the earth’s centre, it passed through a rainbow. Because of its colourful occurrences, tourmaline has been confused with other gems throughout history.
How to Buy Tourmaline
No two tourmaline gems are exactly alike, which makes this a one-of-a-kind gift for any individual—especially someone celebrating an October birthday or an eighth wedding anniversary. With a wide variety of colours, qualities and sources available, there’s tourmaline to suit a range of styles and budgets. Like diamonds, tourmaline is evaluated by the criteria of: colour, clarity, cut and carat weight.
Colour – In general, darker toned tourmaline that appears black is priced much lower than brightly coloured material. Rubellite tourmaline, in shades of pink or red, is one of this gem’s most desirable colours.
Green and blue tourmaline are also popular, though the most striking shades of these colours come from Brazil’s exotic Paraíba tourmaline. At about $10,000 per carat, this is the most valuable variety of tourmaline.
Clarity – Inclusions are common in tourmaline, because liquids can get trapped as bubbles during crystallisation. It’s not uncommon for red or pink tourmaline to display visible inclusions, but inclusions can drastically lower the value of other colours. Some tourmaline material, especially rubellite, undergoes heat treatment to improve colour. Other tourmaline is clarity-enhanced to remove inclusions, which can significantly lower the value.
Cut – Because tourmaline forms in slender, columnar crystals, many finished gems have long, irregular shapes. Tourmalines tend to absorb light down the length of a crystal, rather than across it. This makes these gems “pleochroic,” which means they appear different colours from different directions—so the cut is critical.
Carat Weight – Paraíba tourmaline is rare in sizes larger than one carat. But with these stones, colour is more highly valued than size, so a small, brightly coloured gem is preferred over a large, dark one.