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December Birthstone: Tanzanite


Family: Zoisite

Color: Blue to violet to bluish purple

Mohs Hardness: 6-6.5

While working in education at Tiffany & Co., one of my primary job functions was to write the history of gemstones and diamonds from a Tiffany perspective. I painted Tiffany as the source of all gemstone enlightenment, knowledge, and culture. In the copy I wrote, I positioned the company as the ultimate leader in all things gems.

While Tiffany's current assortment doesn't boast much in terms of colored gemstones and Tiffany's touch on the diamond industry today is a cursory glance due to the company's vertical integration, it was all too easy to speak about the history of gemology, the discovery of gemstones, and Tiffany's leadership while glowing the infamous Tiffany Blue. In my job, I mixed the gemological kool aid and drank it because Tiffany is the source of kool aid.

The History of Tanzanite

In 1967, in the foothills of Tanzania’s Mount Kilimanjaro, a lightening storm flashed across the landscape, charring trees and bushes, leaving devastation in its wake. Well, devastation and small bluish-purple pebbles that the Masai tribesmen gathered in fistfuls.

When a box of these never before seen bluish-purple gemstones landed on the desk of Tiffany's President, Henry Platt, he named this new glorious gemstone "Tanzanite" after it's birthplace ad only source: about 8 square miles in Tsavo National Park in Tanzania.

In 1969, Tiffany released Tanzanite into its stores, telling the romantic story of the gemstone's discovery in its advertisements.

"Today, Tanzanite can be found in significant quantities in only two places in the world.

In Tanzania. And Tiffany's."

Well done, Don Draper!


Tanzanite's popularity has exploded since it first hit the market in Tiffany stores in 1969. Today, cruise ship ports are brimming with the gem, Tanzanite is December's Birthstone, and it is a favorite among clients looking for a beautiful Sapphire-like gem. In fact, it is said (cough BY TIFFANY cough) that Tanzanite is the most important blue gemstone discovered in over 2000 years!

So what happened when that lightening storm destroyed the terrain and transformed the trees to shiny blue rocks? Turns out, exposing the mineral Zoisite, which is a colorless, gray, yellow, brown, pink, green, blue, and violet mineral, to 600 degrees Celsius heat for 30 minutes transforms the dull mineral to beautiful shades of blue and violet. This is a very mild heating treatment (almost all rubies and sapphires are heated to over 1200 degrees Celsius for DAYS!) and virtually all Tanzanite is heat treated. This is a stable, industry accepted treatment.

This is is a photo I took of a pile of Zoisite that was NOT treated. Note the yellows, browns, greens, and soft purples of this stone:

Tanzanite Quality:

Tanzanite comes in a wide range of quality. The closer the gemstone comes to the rich blues we see in Sapphire, the more valuable it is. Strong-to-vivid blue, purplish blue and violetish blue color with nice tone are considered the most valuable.

One of the main determinants in the color we see in Tanzanite is the angle at which the stone is positioned. Tanzanite is a pleochroic gemstone that takes on a different hue based on the angle from which it is viewed. From different angles, the same stone can appear blue, violet or red.

A skilled gem cutter (lapidary) will position the blue angle up, so the gem takes on a closer resemblance to Sapphire.

Tanzanite Care

As Tanzanite is a relatively soft gemstone, achieving a 6.5 on the Moh's scale, it is important to take extra care while wearing Tanzanite. It is not recommended to wear a gemstone with a hardness less than 7 in every day use, especially in rings. To care for you Tanzanite, do not use ultrasonic cleaning and avoid sudden temperature changes.

I am a big fan of Tanzanite in all of its qualities. The periwinkle purple was the color of the Tanzanite pendant that was my first piece of fine jewelry. That color will always have just as much value to me as the most highly coveted Sapphire-blue Tanzanite's on the market as a result.

Tanzanite is a complex gem with lots of personality and flavor and a rich Tiffany Blue History that I will always hold dear.

Tanzanite photo by Original Eve with the Terrace Ribbon Ring

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