Andalusite - Al₂OSiO₄

Habit: Pale to deep pink or reddish brown, white, gray, violet, yellow, green or blue. Euhedral crystals or columnar aggregates with nearly square cross-sections, commonly elongated; also fibrous, compact or massive. Vitreous luster; transparent to opaque. White streak.

Environment: Characteristic of low-grade metamorphism of pelitic sediments (clastic rocks with a grain size of less than

Etymology: From the province of Andalusia in Spain.

Andalusite is a strongly pleochroic gemstone, meaning that it displays different colors depending on the direction from which it is viewed — in this case, shades of yellow, olive and reddish brown. Depending on the cut, each stone has two colors that differ in intensity or blend into a mosaic; cutters try to orient the gem to get the most pleasing mix.