Sapphire has an infinite number of grades: Grades are entirely arbitrary and are decided upon after inspection of each synthetic sapphire batch which has been grown. There are also many growth methods. Guild Optics has found that the best optical grade sapphire comes from the H.E.M. and Kyropoulos growth methods.
- Synthetic sapphire is graded by what is important for a particular application, either optical or mechanical
- A high grade of sapphire would have little or no light scatter or lattice distortion and be used mainly for the most demanding optical applications
- A lower grade of sapphire may have extensive light scatter or lattice distortion, being used mainly for mechanical and structural uses such as bearings, fixtures, and less demanding optical applications
- An ultraviolet (UV) grade sapphire or non-browning sapphire will not solarize on exposure to UV light
- An infinite number of grades fall between the high and lower synthetic sapphire grades, with each sapphire manufacturer giving a name to their own grades