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Tourmaline

Tourmaline is a popular choice amongst jewellers primarily for its incredible range of colours.  Tourmaline’s many varieties represent the entire spectrum of colours. 

 
Tourmaline - Semi-Precious stone
Bicolor Tourmaline

Commercially, there are many trade names given to specific colours of tourmaline and many people may be unaware that they are tourmalines. 

Some examples include: rubellite for red tourmalines, indicolite for dark blue tourmaline, and paraïba for vibrant neon blue and bluish-green tourmalines coloured by the presence of copper in their structure.  The term “paraiba” has been the subject of great debate in the gem industry. Some believe that the term should be reserved for copper bearing tourmalines that are from Brazil’s Paraïba province while others claim that any copper bearing tourmaline, regardless of origin, can be called Paraïba. For bright blue stones that come from deposits outside of Brazil it is preferable to use terms such as ‘paraiba-like’ or ‘cuprian’ (meaning copper bearing).

It is not uncommon to find tourmalines that show more than one colour at a time. In some cases rough crystals show pink cores surrounded by green exteriors.  Tourmaline with these concentric colour zones is often sliced like its namesake “watermelon” to showcase the contrasting colours. In other cases different colours appear along the length of the crystal and often these “parti-coloured’ tourmalines are fashioned to show multiple colours in the same stone. Tourmaline can also display a cat’s eye effect.

Where can you find the tourmaline you need?

Pierres de Charmes carries a vast selection of fine quality tourmaline.  Our collection of well-cut stones includes many different shapes and sizes including calibrated stones. 


Tourmaline

Tourmaline

3,50 mm also in the picture : alexandrites and emeralds

Tourmaline

Tourmaline

Available in 2,50 mm - 3 mm - 4 mm - 5 mm - 6 mm - 7 mm - 8 mm - 9 mm and 12 mm

Tourmaline

Tourmaline

Ref. # 1354 - 5,00 mm

Tourmaline

Tourmaline

Ref. # 1356 - 6,00 mm - 1,09 ct

Tourmaline

Tourmaline

Ref. # 1359 - 5,50 mm - 1,67 ct for the pair

Tourmaline

Tourmaline

Ref. # 1499 - 5,00 mm

Tourmaline

Tourmaline

Ref. # 1503 - 4,00 mm

Tourmaline

Tourmaline

Réf. # 1780 - 6,00 mm and ref. # 2614 - 5,00 mm

Tourmaline

Tourmaline

Ref. # 1781 - 9,00 x 7,00 mm

Tourmaline

Tourmaline

Ref. # 1782 - 4,50 mm - ref. 2615 - 4,00 mm

Tourmaline

Tourmaline

Réf. # 181 - 13,09 x 6,95 mm - 3,46 ct

Tourmaline

Tourmaline

Ref. # 1839 - 9,00 mm - 7,45 ct for the pair

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Tourmaline Fact Sheet

As a general rule tourmaline is stable and resistant with a hardness of 7 to 7.5 on the Moh’s scale. However, some tourmalines may have numerous fracture-like inclusions that can weaken the stone. Tourmaline of all colours has a vitreous luster.

Fact sheet

Chemical composition  

Complex boro-silicate of aluminum, magnesium and iron

Crystalline system 

Trigonal

Cleavage

Difficult and indistinct 

Refractive index

1.624 – 1.644

Birefringence  

0.018 – 0.040  

Specific gravity

3.00 – 3.10

Anisotrope  

Two different tones of the stone’s body colour. The lapidary must pay special attention to this characteristic if he wants to display the best colour in the facetted gem.

 Gemmologists can use many different instruments to distinguish tourmaline from similar looking gemstones. The microscope is particularly useful as tourmaline often has a very recognizable inclusion consisting of fine liquid filled canals that can resemble tangled hairs. Tourmaline’s high birefringence helps to identify it and can sometimes be seen with the naked eye as a ‘doubling’ effect of the facet edges when viewed through the stone. 

Producing Countries

Much of the world’s tourmaline comes from deposits in Brazil. Other producing countries include: Mozambique, Madagascar, Namibia, Tanzania, Afghanistan, Pakistan, Russia, and the United States.

Tourmaline crystals often form in pegmatites. They are typically long 3, 6, or 9-sided prismatic crystals with slightly rounded and heavily striated (lengthwise) prism faces.

Is tourmaline treated?

Tourmaline can be heated to lighten dark tones or irradiated to intensify the colour. The latter is often used to achieve the rich reds of rubellite. Colours resulting from these treatments are stable.

Many Paraïba-like copper bearing tourmaline start out as violet, pink or grey stones. A heat treatment is used to create the electric blue and greenish blue colours associated with paraïba tourmaline.

As with many gems that have surface-reaching fractures, tourmaline can be fracture filled using oils or resins.  Oils improve the appearance of the gem by making the fractures less visible.  Resin fillers will have the same visual effect while also enhancing the gem’s durability.  Presence of these treatments should always be divulged.

Tourmaline in Jewellery

Tourmaline is widely used in jewellery and its growing popularity stems from its incredible range of colours and its durability. Many tourmalines available in the market are relatively affordable compared to other gems.  Tourmaline is the birthstone for the month of October and it is the gemstone for the 8th wedding anniversary.

Value and Quality Criteria

Colour is the primary consideration when it comes to value; the more vivid and intense the colour the more valuable the gem. Clarity also plays an important role in value and, in general, green and blue tourmalines have fewer inclusions than red and pink varieties. Therefore slightly included pink and red tourmalines are judged less harshly than included blue and green stones.

The quality of the cut as well as the choice of cut style can also influence value.  Tourmaline is most often found as elongated crystals and this explains why many facetted tourmalines are rectangular in shape.  As with all gems, size has a direct impact on value. Currently there are fewer large rough tourmalines being found and this is reflected in the market with larger facetted stones selling at a premium.

Fun Fact

As recently as the 18th Century tourmaline was often mistaken for other gems with green tourmaline being confused with emerald, rubellite being taken for ruby and indicolite believed to be sapphire. Even the name tourmaline comes from toramalli meaning “mixed gems” in Sinhalese.

 

(2010). Tou-1. In Cours de base en gemmologie Gem-A. London.

 Schumann, W., Georges-Catroux, F., &Poirot, J. (2014). Citrine. In Guide des pierres précieuses: Pierres fines et ornementales: 1900 échantillonsphotographiés (p. 128). Paris: DelachauxetNiestlé.

Gem property Chart A [Chart]. (n.d.). In Gemological Institute of America (GIA). 1992

Civitello, O. (Trans.). (2010). Tou-1. In Cours de base en gemmologie Gem-A. London. 

What Is Tourmaline Gemstone | Tourmaline Stone – GIA. (n.d.). Retrieved July 25, 2016, from http://www.gia.edu/tourmaline 

Tourmaline Quality Factors. (n.d.). Retrieved July 25, 2016, from http://www.gia.edu/tourmaline-quality-factor