Tourmaline

Colour colourless, yellow, pink, red, brown, green, blue, purple, black Pleochroism: medium to strong in the colour shades of the gemstone Mohs’ hardness: 7.0 - 7.5 Density: 3.02 - 3.26 Cleavage: absent Fracture: irregular, fragile, conchoidal Crystal system: trigonal, generally long shaped Transparency: transparent to opaque Lustre: vitreous lustre Fluorescence: absent

Dutchmen brought the Tourmaline from Sri Lanka in 1703. There are several classes, differentiated by colour: Achroite: very rare, colourless Rubellite: pink to red, purple; in its most appreciated variety, Ruby red Dravite: brown yellow to dark yellow Verdelite: green tones; the most valuable one is the Emerald green one Indigolite: blue Siberite: red, purple, blue-lilac; when very red-pinkish, equivalent to Rubellite Schorl: black, very common

In the same Tourmaline crystal there are different tones or colours, which sometimes change under different type of lights. Through strong temperature changes, high pressure or polishing, they can be loaded with static electricity. Dutchmen called this gemstone ‘Aschentrekker’ (ash vacuum cleaner), because they extracted the ashes from their pipes with heated Tourmalines. The most precious colours are pink, red and green. If they are heated up to 450-650C, they can slightly change their colour: green Tourmalines turn into emerald green and red-brownish ones into a luminous red.

In Sri Lanka, Madagascar, Brazil, Mozambique, Angola, Australia, India, Tanzania, Thailand, the Urals, USA and Switzerland.

Tourmalines are very versatile for cutting. The overall best cuts for this gemstone are emerald cut, oval cut and cabochon. Due to its strong pleochroism, darker colours are cut parallel to the principal axis. Lighter stones are cut perpendicularly to the main axis, in order to darken the colour.

Because of the great diversity of colours, it can easily be confused with amethyst, citrine, peridot, smoky quartz, ruby, emerald, topaz, zircon and some crystal imitations.