Tourmalines have a wide variety of exciting colours with one of the widest colour ranges of any gem.

Tourmaline is renowned for its stunning variety of colours, boasting one of the broadest colour ranges among gemstones. From vibrant pinks and purples to a spectrum of nearly every hue, tourmaline offers an array of options that can rival even the finest sapphires.

Several colour varieties of tourmaline are known by their own trade names:

• Rubellite refers to pink, red, purplish-red, orangy-red, or brownish-red tourmaline, although some experts believe this term should be reserved for deeper reds.

• Indicolite describes dark violetish-blue, blue, or greenish-blue tourmaline.

• Paraíba is a term for intense violetish-blue, greenish-blue, or blue tourmaline originating from the Paraíba state in Brazil.

• Chrome tourmaline features intense green hues, primarily coloured by vanadium, similar to the element that colours many Brazilian and African emeralds.

• Parti-coloured tourmaline displays multiple colours, with green and pink being the most common combination, though many other colour pairings are possible.

• Watermelon tourmaline has a distinctive appearance with pink at its centre and green on the outer edges, often cut into slices to highlight this unique arrangement.

Tourmalines can also exhibit a cat’s-eye effect, known as chatoyancy. This effect is most commonly seen in green, blue, or pink tourmalines and is caused by numerous fine, tube-like inclusions within the crystal. Unlike the sharp chatoyancy of fine cat’s-eye chrysoberyl, tourmaline’s chatoyancy appears softer and more diffuse due to the larger size of these inclusions. To showcase this effect, tourmalines are typically cut as cabochons.

The colour of tourmaline is influenced by its chemical composition, which includes elements such as silicon, aluminium, and boron, along with a complex mix of other elements like sodium, lithium, calcium, magnesium, manganese, iron, chromium, vanadium, fluorine, and occasionally copper. These elements contribute to the diverse range of colours found in tourmaline.

Tourmaline is classified into several species based on its chemical composition:

• Elbaite is the most common gem-quality tourmaline, found in colours ranging from green, blue, and yellow to pink, red, and even colourless. Elbaites are often found in granite-containing pegmatites, which can yield very large crystals and a variety of colours from different pockets within the same deposit.

• Liddicoatite, named after Richard T. Liddicoat, a prominent gemmologist, contains calcium, lithium, and aluminium. It is found in pegmatites and is known for its complex internal zoning and diverse colours.

• Uvite is rich in calcium, magnesium, and aluminium, and forms in limestone that has been altered into marble by heat and pressure.

• Dravite contains sodium, magnesium, and aluminium, and like uvite, it is found in altered limestone.

Dravite and uvite often mix to form tourmalines in colours such as brown, yellowish-brown, reddish-brown, or nearly black. These may contain traces of vanadium or chromium, producing green hues that can rival tsavorite garnet and sometimes emeralds. Yellow tourmalines, sometimes called “savannah” tourmalines, derive their colour from iron.

Schorl is a common black variety rich in iron, found in various rock types but rarely used as a gem, except in mourning jewellery.

The wide range of tourmaline colours results from different elements and processes. Iron and possibly titanium induce green and blue colours, manganese creates reds and pinks, and radiation (either natural or induced) can affect pink and yellow hues.