Tourmaline

Probably, tourmaline has been used in jewellery for centuries because people confused it with other gems. 

For example, in the 15^th century was discovered in Brazil a deposit of green tourmaline that Portuguese thought was Emerald.

Fortunately in late 18^th century tourmaline found its identity, thanks’ to the work of a gemologist who wrote about this special gem.

The name comes from “toromalli”, the Sinhalese word for “mixed gems”.

It comes in different colors, actually is the gem with the widest color range of all. It has several shades of almost every hue. And very often it has colors that you can’t find in other natural gemstones.

 Some colors have their own trade names:

rubellite

paraiba

Rubellite: with colors that go from pink to red and purple.

Paraiba tourmaline: take the name from its source, the color is a bright violetish blue o greenish blue.

Watermelon tourmaline: has a pink centre and a green outline.

 Indicolite: is dark violetish blue.

indicolite

watermellon tourmaline

parti-colored tourmaline

Parti-colored tourmaline: has more than one color, it has a vary combination, the most common are green and pink. The color zoning happen when trace elements change composition during the crystal’s growth.

pleochoic colors visible under
dicroscope lents

The crystal has usually an elongated shape, which force cutters to create an elongated final shape and proportion. The rectangular is the typical cut.

But when the crystal is well formed, is not cut, for collectors it has more value than fashioned gems.

Tourmaline is pleochroic: which means that depends from the point of view, it  looks in a different color, usually one of the pleochroic colors is slightly darker than the other.

The cutters have to pay attention to the pleochroism, they have to finish the gem giving the best color from the top right view.

Brazil is probably the largest producer of tourmaline of the world. One of its products is the Rubellite, the trade name for pink-red tourmaline.

In 1989, a rare blue tourmaline has been discovered in Paraiba state, the color is so rare and attractive that very quick this stone became the most priced gem of the market.

When the chemical composition of tourmaline has some chromium as trace elements that cause the color of the gem, in the trade is called chrome tourmaline. The hue of the crystal goes from bluish-green to yellowish green. Like the Paraiba one, this variety is relatively new in the market, it started to appear in late 1960’s.

If the stone has some needle like inclusions and is cut properly, it can shows the phenomena of the cat’s eye: the inclusions reflects the light as a bright line that resemble the eye of a cat.

The two most used treatments of tourmaline are heat and irradiation. They are never used to change the hue of the stone, but actually to lighten and brighten the original color. For example, many Paraiba tourmalines are treated to remove some greyish hint and give a spectacular bright blue color.

Usually those treatments are stable and undetectable.

Tourmaline is a piezoelectric material, that’s why you can see lighters, flat iron or watch made with those crystals.