There is as yet no universally accepted method of grading for Tanzanite. Indeed, the world's most recognised laboratories have yet to reach consensus on terms used for grading Tanzanite although the top gradings on most systems will be similar. Below is an example of how tanzanite is graded by HKD Diamond Laboratories in Canada:
This is arguably the most viable grading system because as can be seen in the other examples 'Blue Dominant' and 'Violet Dominant' we see what many refer to as 'QUESTIONABLE GRADING SYSTEMS' (Ian C.C. Campbell). These are utilized in many countries worldwide, and as Ian Campbell argues 'these show parameters that really do not make much sense, other than to glorify a stone to an absurd degree of high quality'.
Blue Dominant
Violet Dominant
