Kyanite, also known as aluminum silicate, is a bluish-green to colorless mineral typically found in metamorphic rocks. This mineral is used commercially in the production of some ceramics, and it is also sometimes cut for use as a gemstone. Often, the mineral is used in the ceramic mixes used to make plates, spark plugs, toilets, and many other household goods. The world's major supplies of kyanite come from the Ural Mountains in Russia, as well sources in Italy, Switzerland, and the American Northeast; the mineral can also be found in other deposits around the world.
Classified among the aluminosilicate minerals, this mineral is made up primarily of aluminum, oxygen, and silicon; accordingly, it tends to turn up in locations that are rich in aluminum. It is also considered to be a polymorph of andalusite and sillimanite, which means that these minerals share identical chemical compositions, but their crystalline matrixes are different. The crystal formation is impacted by factors like heat and pressure, so these minerals can sometimes be used as indicators of geologic history when they are found. It is a brittle material, so if it is used for gemstone cutting, it must be cut carefully.
Several things make kyanite distinctive; the first is the shape of the crystals, which tend to form in elongated columns. The second is the fact that the mineral is anisotropic, which means that the hardness varies with the direction of the crystals. People can test the anisotropic properties of kyanite for themselves by scratching various crystal faces on a sample of this mineral; this test is often used in the field to make a positive identification of kyanite.
The name for this mineral comes from the Greek kyanos, which means “blue.” Some specimens have an incredibly rich blue color, making them excellent candidates for gemstone cutting. While some specimens are blue, most samples of kyanite are transparent, with a slightly pearl luster. The mineral may also be streaked with white or other colors, depending on impurities in the mineral, and it is often attached to other minerals such as garnets, quartz, and various micas. Mineralogists often keep samples of unprocessed kyanite around because it is an interesting mineral, and some collectors keep it as well, especially when they find richly colored samples.