Indicolite

Indicolite is the trade name for blue, dark violetish blue or greenish blue tourmaline; most of these stones are elbaite, a lithium-bearing kind of tourmaline. Its colour comes mainly from traces of iron, and possibly titanium. The name was proposed in 1800, as “indigolith”, by the Brazilian naturalist d'Andrada for the bluish green tourmaline of the Swedish island of Utö. It is kept apart from the neon-blue, copper-coloured Paraíba tourmalines.

Jewellery: Clear, lively blue crystals are faceted for rings, pendants and earrings. Its hardness (7–7.5) suits everyday jewellery. Collecting: Blue crystals from pegmatite pockets, on lepidolite or quartz, are kept in museums and collections. History of science: Tourmalines from Utö were used in some of the first analyses to show that tourmaline contains boron and lithium.

It has a hardness of 7–7.5 on the Mohs scale. It scratches glass and steel; a steel knife cannot scratch it. Its specific gravity is 2.82–3.32 g/cm³.

Its best-known localities: Utö, Södermanland, Sweden; Kwara State, Nigeria; São José da Safira, Minas Gerais, Brazil; Paprok, Nuristan, Afghanistan; Erongo Region, Namibia.

Its colour runs from light sky blue to dark violetish blue and greenish blue. It is strongly pleochroic: the stone looks light blue from one direction and very dark blue from another. Its hardness is 7–7.5; it has no distinct cleavage but is brittle. Its refractive index is about 1.614–1.666 and its double refraction is marked (0.014–0.040); these values help to tell tourmaline from similar blue stones. Heat treatment: dark indicolites are routinely heated to lighten their colour. The treatment is common and often undetectable.

On the “street to diamond” value ladder it sits on step 6 of nine: Fine ornamental and collector stone. Colour matters most for indicolite: lively, medium-toned, pure blue stones are the most sought after, while very dark stones or those leaning towards grey or green are worth less. Because of its strong pleochroism, how the cutter orients the stone directly affects its colour. Heat treatment is common. Ordinary blue indicolites are relatively affordable; neon-blue stones coloured by copper count as Paraíba tourmaline and are worth far more, so a laboratory report matters.

Today crystal-therapy websites and stone sellers claim that indicolite is linked to the throat and “third eye” chakras, strengthens communication and intuition, brings peace, and develops psychic abilities such as mediumship. There is no scientific evidence that indicolite strengthens communication, intuition or psychic abilities. Its blue colour comes from traces of iron in its crystal structure; it is simply a physical property of the stone. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.