Indigolite tourmaline is a quite rare type of tourmaline.
It can be of the following hues: blue, dark blue, blue-green, bluish-black.
It got its name from the color "indigo."
And the color "indigo" is named so after the plant of the "Indigofera tinctoria", which grows in India. A dye was extracted from this plant and was widely used for dyeing clothes.
Sometimes the "indigo" color is called "Indian blue."
In general, experts call indigo one of the first dyes on the Earth that has reached our days, it was used in ancient civilizations - Egypt, Mesopotamia, Ancient Greece and Rome, not to mention India itself and the countries of Southeast Asia.
They mainly dyed silk and wool with indigo.
Cuneiform clay tablets were found whose age scientists date approximately to the 7th century BC, which describe a recipe for dyeing wool with indigo.
Naturally, this natural dye was an item of luxury, and clothing of the corresponding colors was a marker of the nobility and wealth of its owners, and in completely different societies - from the nomad Tuareg people of West Africa to the aristocrats of East Asia.
Nowadays, indigo dye is not extracted from plants, but it is artificially synthesized.
By the way: if you mix the leaves of Indigofera tinctoria with henna, you will get black hair dye – basma.