Gemstone treatment
Heat Treatment, Tanzanite
Brownish, yellowish, or greenish zoisite changes to blue-violet. Pleochroism remains visible but brown components are reduced.
01
What to look for
Brownish, yellowish, or greenish zoisite changes to blue-violet. Pleochroism remains visible but brown components are reduced.
02
What it means
Nearly all commercial tanzanite is heated. The treatment is stable and widely accepted.
03
Expert move
Unheated blue tanzanite is uncommon. A brown or green component may suggest unheated material, but lab confirmation is needed.