Kyanite is one of the most attractive blue minerals in nature. It sometimes exhibits intense shades of blue or even multiple shades with color zoning in a single crystal. The color of Kyanite, combined with its well-formed and sometimes large crystals, make this mineral appreciated by both novice and expert collectors alike.
Kyanite is strongly anisotropic, meaning it has a different hardness depending on the angle. In fact, it is the most well-known anisotropic mineral. The vertical hardness of Kyanite ranges from 4.5 to 5.5, and horizontal hardness from 6 to 7. Kyanite is named from the Greek term cyanos, which means deep blue, alluding to the typical color of this mineral.