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.** This particular specimen is a darker blue than most - but is a great example of the "angles" or blades. 2.27 oz, 3" x 1.25" at its widest end
