- Color: blue, greenish blue, yellow, pink, colorless
- Hardness: bi-directional, 4.5 - 7
- Refractive index: 1.71 - 1.74
- Density: 3.53 - 3.70
- Chemical composition: Al2O[SiO4]
- Crystal structure: triclinic
- Origins: Brazil, USA, Switzerland, Kenya, Mozambique, Russia, Nepal, India, Burma.
The hardness of a kyanite varies depending on differing crystal axial directions from 4.5 to 7. The best stones are intense blue and have a uniform color throughout the crystal.