This is basically the blue variety of tourmaline, but it may also be greenish blue or otherwise vary from the indigo color suggested by its name.
Appearance Generally indicolite is 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.
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. This gem is given mixed faceted and also rectangular, step cuts. It generally has good luster.
Distinctive features The 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. Mid-blue zircon, with three times the birefringence, also shows this effect, but to a far greater extent, and is a very different, lighter color, with greater luster.
Occurrence lndicolite is mainly found in Brazil (state of Minas Gerais), but also in the United States (Colorado. Massachusetts, California), Namibia, Madagascar, and the Soviet Union (Urals).
Value Attractive, definite blue, bright 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. .
Simulants and synthetics It is neither imitated nor produced synthetically.