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Tanzanite Grading Reports

The AGTA Gemological Testing Center (GTC) offers Tanzanite Grading Reports in accordance with the Tanzanite Quality Scale™. The Tanzanite Quality Scale™ is a tanzanite specific, internationally recognized tanzanite grading system developed by the Tanzanite Foundation. The Tanzanite Foundation's vision is to establish a universal standard for grading tanzanite so as to facilitate for trade and consumer confidence, encourage a more comprehensive and consistent understanding of tanzanite's qualities and rarity, as well as encourage the development of a more formalized industry.

In 2002, the AGTA selected tanzanite as a December birthstone, adding it to a list of birthstones unchanged since 1912.

The Tanzanite Quality Scale™ grades according to specific standards under the 4 C's criteria of Carat Weight, Color, Clarity and Cut. A fifth "C" stands for Confidence. Tanzanite Quality Scale™ grading certificates issued by AGTA GTC will provide the assurance that the tanzanite inspected is accurately graded, authentic and of natural origin, from the world's only known tanzanite source situated at the foothills of Mount Kilimanjaro in Tanzania, East Africa.

 

Tanzanite Grading Report, front
Tanzanite Grading Report reverse
The front and reverse of the AGTA GTC Tanzanite Grading Report. Click on an image to view a high-resolution version.

 

Mount Kilimanjaro
Mount Kilimanjaro, as seen from just outside Block D at Merelani, Tanzania. At 5,895 meters (19,341 ft), its summit is the highest point on the African continent. Photo: Richard Hughes, Oct. 2007.

Tanzanite Grading

The AGTA GTC Tanzanite Grade is based upon the Tanzanite Quality Scale™ developed by the Tanzanite Foundation™, according to the 4C’s: Color, Clarity, Cut and Carat Weight.

Color

Tanzanite is color graded according to a combination of hue position and saturation using a daylight-equivalent grading light (approximately 5000–5500° Kelvin) with the gem in the face-up position. Saturation ranges from Exceptional to Pale, with a “B” (blue) or “V” (violet) indicating the dominant hue position. In the rare circumstance that saturation exceeds Exceptional, it will be graded as Exceptional (+). All other factors being equal, the more saturate the color and blue the hue, the more valuable the tanzanite. Tone is also a factor, with the ideal being not too light or dark.

Grade
vB
bV
E = Exceptional Blue tanzanite colors Violet Tanzanite Colors
V = Vivid
I = Intense
M = Moderate
L = Light
P = Pale
15.42 carat tanzanite
This spectacular 15.42-ct gem is an example of the Exceptional + vB grade, the summit of tanzanite color. Photo: Wimon Manorotkul/Pala International; tanzanite courtesy of Robert Hughes.

 

Clarity

Clarity is graded according to the number, visibility and type of inclusions. Magnification is used, but final grades are set with the unaided eye. Grades ranges from Eye Clean to Heavily Included. Eye Clean stones are those in which inclusions are extremely difficult or impossible to see with the unaided eye in the face-up position. Eye Clean stones do not possess any inclusions which might impact the durability or beauty of the gem. All other factors being equal, the less included the gem, the more valuable it is.

While some have argued that the top grade should be "loupe clean," this makes little sense, as gems are not designed to be worn with attached loupes. The reality is that loupe-clean and eye-clean gems are identical in appearance and durability.

Others suggest a "loupe clean" grade on the basis of rarity. But the rarity question is important only insofar as it relates to beauty. If rarity alone is the consideration, then every gem is equally rare, as no two individuals are identical. Rarity cannot be divorced from beauty.

 

Tanzanite Clarity Grades
Tanzanite clarity grades illustrated.

 

Cut

The overall cut grade is a synthesis of a tanzanite’s brilliance, scintillation, proportions and finish when viewed by an expert grader with the unaided eye. It is judged on a scale from Excellent, Very Good, Good to Fair. An “Excellent” cut ensures that the stone’s facets reflect light to create maximum brilliance and scintillation.

 

Tanzanite Clarity Grades
Differences in light return for well-cut gems, as opposed to those that are too deep or too shallow.

 

Carat weight

The metric carat is equal to one fifth of a gram. Generally, a large stone of a given quality is more valuable than a smaller stone of identical quality.

 

Tanzanite Clarity Grades
Hundreds of feet down one of the shafts at TanzaniteOne's Block C concession, miners remove tanzanite-bearing ore. Photo: Richard Hughes, October 2007.