Kyanite is a mineral infrequently cut as a gemstone. It occurs in light to dark blue, green, colourless and brown colours in a transparent form with the blue color being most used in gemstones. Kyanite is of interest because of the extreme variablity in hardness with direction. In one direction, the hardness is 4.5 and in the other it is 7. Very easy cleavage is encountered in one direction with a less perfect cleavage occurring at 74 degrees to the first. The finest gem quality Kyanite may be confused in appearance with spinel or blue sapphires from Burma and ceylon.From the Kali-gandahi region of tibet.comes from the greek word for blue kyanos..blue as pretty as the very rare cobalt blue spinel . Known Facts Color Key: Blue, Greenish Blue. Refractive Index: 1.716 – 1.731 Chemical Composition: AL2SIO5 Hardness: 4.5 – 7.0 Density: 3.56 – 3.68 Crystal Group: Triclinic Ocurrence: Kenya, Nepal, India, Burma,U.S.A.