Kyanite or aluminum silicate is a bluish green to colorless mineral which is 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. The world's major suppliers of kyanite are in the Ural Mountains, Italy, Switzerland, and the American Northeast; patches of the mineral can also be found in other deposits around the world.

This mineral is classified among the aluminosilicate series, and it tends to turn up in locations which are rich in aluminum. It is also considered to be a polymorph of andalusite and sillimanite, meaning that these minerals share identical chemical structures, but their crystalline matrixes are different. Because the crystal formation is impacted by factors like heat and pressure, these minerals can sometimes be used as indicators of geologic history when they are found.

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 which makes them excellent candidates for gemstone cutting, although kyanite can be brittle, so care must be taken to cut the mineral carefully. 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.

Most samples of kyanite are transparent, with a slightly pearly 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. You may have kyanite in your home or vehicle; the metal is used in the ceramic mixes used to make plates, spark plugs, toilets, and many other household goods.