Coatings used to give tanzanite a deeper (blue) color? The American Gem Trade Association Gemological Testing Center (AGTA-GTC) and American Gemological Laboratories (AGL) received a number of faceted tanzanite samples recently in New York that were determined to have been treated with a coating. Evan Caplan of Omi Gems Inc. sent samples to several labs […]Continue reading »
Tanzanite Consumer Information
As provided and validated by various gemmological organizations, laboratories and the "World Jewelry Confederation CIBJO"
also trichroic, meaning that light entering the gem is split into 3 different wavelengths. As a result, tilting the gem in 3 different directions one is sometimes able to see 3 different colors. Tanzanite is extremely light sensitive, with incandescent lighting tending to shift its color to the violet side. The best pieces show an intense blue under any light.
therefore eye-clean stones. Fingerprint inclusions are sometimes present. Very rare, tiny, parallel, hollow tubes in some tanzanites cause chatoyancy (cat's eye effect).
styles. Ovals and cushions are the most common, but rounds are also seen, as are other shapes, including emerald cuts, trillions, etc. Cabochon-cut tanzanites are not often seen.
to purplish blue. The yellowish brown colored stones are usually (light) heat treated to result in the blue colors associated with tanzanite.
with damp cloth and/or soapy water only. Tanzanites in large sizes, and rich colour are desirable for collections. Some tanzanites are carved or sculpted by famous lapidary artists and as such are considered collectible. Finally, multi colour transparent zoisites (fancy tanzanites) are also sought, particularly green and pink. On extremely rare occasion, collectible cat's eye tanzanites are fashioned.