Photo of Indicolite in Processed & Rough Form
Indicolite is a mineral with a hardness of 8 out of 10 on the Mohs scale of mineral hardness [?]. These Trigonally structured gems are made of complex borosilicate, their full chemical compound being Na(Li,al)3Al6(BO3)3Si6O18(OH)4.
Indicolite is the blue sodium-rich variety of Tourmaline, and may come in all shades of blue, from light-blue, violet-blue to deep red or deep green.
It generally appears quite a deep blue, even the color of dark blue ink, perhaps appearing green in one direction because of its strong pleochroism. Sometimes indicolite is an overall greenish blue, which, unlike the color of greenish blue sapphire, is very attractive.
Its greenish blue color is unmistakable and particularly attractive. Loss of transparency in one direction is another distinctive characteristic and is best seen in rectangular gems. Because of its appreciable birefringence, if the stone is examined with a standard jeweler's 10x lens, the opposite facet edges look double in certain directions.
Stones are often clear and free of inclusions, but intense pleochroism may make them so dark in one direction as to appear lacking in transparency.
Indicolite Tourmaline is mainly found in Minas Gerais (Brazil), Colorado, Massachusetts, California (USA, Namibia, Madagascar, and the Ural mountains (Russia).
It is also known as blue tourmaline.
It is mistakenly called indigolite or Brazilian sapphire.
What is Indicolite?
Indicolite is a blue variety of tourmaline. Its name comes from "indigo," referring to its deep blue color, which can range from light blue to deep-blue.
Where is it found?
Major deposits exist in Brazil, Afghanistan, Nigeria, and Madagascar. Smaller deposits are found in the USA, particularly Maine and California.
How can I identify Indicolite?
It shows strong pleochroism (color changes when viewed from different angles), has a hardness of 7-7.5, and displays a distinctive blue color that can sometimes be mistaken for sapphire.
What causes its color?
The blue color comes from iron and titanium content in the crystal structure. Different concentrations create varying shades of blue.
What makes it valuable?
Fine quality Indicolite is rare, especially in larger sizes. The most valuable pieces show a pure, vivid blue color without gray undertones. Clean stones above 5 carats are particularly precious.
The specific gravity [?] for Indicolite is 3.06, its refractive index [?] is 1.62-1.64, and its double refraction [?] is 0.018.
History
Indicolite derives its name from the indigo color.
Industrial Usages
This gem is given mixed, faceted, and also rectangular, step cuts, as it has good luster. Attractive, definite blue or blue-green stones are priced similarly to fine rubellites, and are less common. But when the color is too deep, and inky blue, the value falls considerably, as it does with the less attractive rubellites. It is neither imitated nor produced synthetically.
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