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Andalusite is an aluminum silicate, closely related to both silimanite and kyanite. In fact, all three minerals are polymorphs, which means they share the same chemical composition, but possess different crystal structures. Andalusite is a strikingly beautiful gem, but it is largely unknown to the general public and considered to be one of the lesser-known gem types in the trade. Andalusite colors are typically found yellow, yellow-green, green, brownish red, olive and reddish brown.

Andalusite gives a play of different colors because of its strong pleochroism (pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles) along with iolite, kyanite, kunzite, sphene and tanzanite. Andalusite has trichroic pleochroism; when light enters the stone, it is parted into three sections, each containing a portion of the visible spectrum. Andalusite most often occurs translucent to opaque, with transparent gemstone-quality specimens being very rare.

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For many years, andalusite has primarily been a collector's stone, but it has recently attracted a lot of attention from many jewelry designers and it's becoming increasingly popular. Andalusite possesses a good level of durability and hardness that make it making it suitable for any type of jewelry. The attraction of andalusite is greatly owed to its play of color, which can be seen during changes in its viewing angle. Similar effects are also seen when lightning strikes the gem from different directions.

Andalusite is named after the Spanish province Andalusia, where transparent gem-quality crystals were first found in the Ronda Massif near Malaga and described in 1789. Andalusite deposits can be also found in many locations, including Australia, Brazil, Canada, Russia, Sri Lanka, Burma, Madagascar and the USA (California and Colorado).