The heating process has no effect on the initial color of Tanzanite. Only the red/brown axis is removed, leaving the blue/violet hue alone. It should be noted that if the original Tanzanite already has a deep blue hue, the heat will not change its color. Tanzanite's color is primarily determined by the Titanium to Vanadium ratio in its crystal structure.
The heating process of Tanzanite triggers a valence exchange reaction (redox reaction), which improves the purple and blue colors while leaving the titanium colorless. It is difficult to objectively check the nature of Tanzanite treatment, whether naturally or artificially heated. Actually, science has reached its maximum in terms of this matter, it has become even harder to determine these different treatments. However, the final price will not be affected despite the fact that they are heated in different ways.