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Why is Tanzanite Considered One of the Rarest Gemstones in the World?

Updated: Apr 29

What is Tanzanite?


Tanzanite is a highly valued precious gemstone belonging to the Zoisite familyAccording to the story, herders from the Maasai tribe of Tanzania found blue crystals in the Merelani Hills near Arusha, Tanzania. This discovery prompted gem prospector Manuel D'Souza to register claims over the area with the Tanzanian government. Initially, D'Souza thought he was dealing with a discovery of sapphires; however, after gemological testing, the mineral in question was identified as Zoisite. 


Tanzanite, or 'Blue-violet Zoisite' as it is known by its scientific name, is a calcium aluminium hydroxyl sorosilicate mineral that gets its blue colour from small amounts of vanadium inside the crystal. 


The refractive index (or brilliance) is 1.69 - 1.70, which sits above emerald and below sapphire. The higher the refractive index, the brighter the sparkle. The Tanzanite often has a deeper blue but slightly less sparkle when sitting next to a sapphire of similar colour, clarity, and size.


Tanzanite is a reasonably strong stone, rated 6.5 on the Mohs scale of hardness, about the same as steel or granite. Diamond is the hardest naturally forming substance on Earth, ranked at the top of the Mohs scale. Tanzanite is often found in larger sizes, and care must be taken when wearing Tanzanite jewellery so as not to impact the stone on hard surfaces. 



A range of Tanzanite Gemstones Showing Colour Variation
A range of Tanzanite Gemstones Showing Colour Variation

Where did Tanzanite get its name?


Masaai Woman and Child who knew about Tanzanite gemstones
Masaai Woman and Child

Tanzanite was first discovered in 1967 near Mount Kilimanjaro in Tanzania. The late Manuel D'Souza, a famed gemologist, had heard a rumour from the Masaai Tribe that blue crystal was scattered on the surface of a piece of land southwest of Mount Kilimanjaro. He contacted the Masaai Tribe and was taken to the place that is now the Tanzanite gemstone mining area. D'Souza thought he had found evidence of sapphire, but instead, he had located the area which would become the Tanzanite mining area, Something the Masaai tribe had known for generations. Samples were collected and sent away for testing. It was too soft to be sapphire; laboratory testing discovered that it was Zoisite.


Tanzanite was originally called Blue-violet Zoisite. Tiffany, an international jeweller, realized that this name could have been more palatable. He rebranded the newly discovered jewel from Blue-violet Zoisite to the more fitting Tanzanite, a nod to its single geographic origin.


No gemstone has had as much of an impact on the gemstone industry in recent history as Tanzanite. In 2002, the Gemological Institute of America changed the December birthstone to Tanzanite, the only change since the 1950s and the last change there has been.



Where is Tanzanite Found?


The Tanzanite mining area is tiny, comprising a 12-kilometer square plot of land in the shadow of Mount Kilimanjaro.


When initially discovered, the land was so rich with Tanzanite that the crystal could be collected from the topsoil. Now, mining operations use shafts and tunnels that burrow up to 1000 meters deep. The mining area is divided into 4 blocks. Block A and Block C are mined by large operators funded by foreign investment, and Block B and Block D are reserved for small-scale, local miners. Legend has it that the finest Tanzanite crystals are found in Block D.


Each block has been given to a particular interest group, with Block A and C going to mining companies and Block B and D going to local miners. This system of splitting the mining activity up between international companies and local miners allows more of the wealth generated by mining to go to the men and women who work in and near the mines.


Said to be a thousand times rarer than diamond, the mines are suspected of holding over 21 metric tonnes of Tanzanite. Mining is estimated to last until the 2040s when the mines might start drying out.


Tanzanite mines block A, B, C, and D
Tanzanite mine blocks A, B, C, and D

Is Tanzanite Heated?


Tanzanite crystals display strong pleochroism, showing different colours when viewed from various angles. Nearly all strong purple and purplish blue Tanzanite has undergone heat treatment to clarify the crystal and enrich the colour. When heated to 752 - 932 degrees Celsius, the yellow and brown tints vanish, and the blue deepens. Unheated examples are sometimes called Mermaid Tanzanite as they exhibit grey, brown, purple, yellow and green colour tones. Large and clean cuts of Tanzanite look similar to sapphire, making it an attractive alternative to achieving a luxurious, high-end custom jewellery piece, but with a precious gemstone that is more unique than well-known sapphire.


Tanzanite gemstone ring
8.96ct GIA Certified Tanzanite Cocktail Ring

Custom Tanzanite Jewellery Design


The Sapphire Merchant has created some exceptional custom Tanzanite jewellery pieces for our clientele, including Tanzanite engagement rings.


Tanzanite is an excellent option for people looking for a sizeable precious gemstone with deep, vibrant blue and violet hues. It works well framed with diamonds and can be the centrepiece of a ring or necklace that will grab the attention of all who see it.


The beautiful colours captivate, engage, and engross anyone discovering this rare earth treasure.




Our most recent custom jewellery masterpiece is this 8.96ct GIA-certified Tanzanite from Block D. In a perfect asscher cut, our client wanted something simple, where the Tanzanite was indeed the star of the show. This functional and beautiful design was finished in 18k white gold, with bezel detail down the band. The result is an elegant Tanzanite cocktail ring that will be admired and loved for many years to come.



The GIA Report for our 8.96ct Asscher Cut Tanzanite
The GIA Report for our 8.96ct Asscher Cut Tanzanite


Famous Tanzanite Jewellery Pieces


The Queen of Mount Kilimanjaro Tiara is one of the most notable Tanzanite jewellery pieces. This astounding tiara is held in the private collection of former Apple president Michel Scott. The tiara features 803 tsavorites, a vivid green grossular garnet only mined in the Merelani region of Tanzania, the same area where the Tanzanite blocks are located. In addition to the tsavorites, the tiara features 913 diamonds, set in a sinuous pattern. to resemble a hooded King Cobra snake. The centrepiece of this exquisite crown is a 242-carat faceted Tanzanite in a cushion cut.


The Queen of Kilimanjaro Tiara featuring 242 Tanzanite
The Queen of Kilimanjaro Tiara

In collaboration with Harrod's and Disney, Chopard created the magical Belle Necklace for the Swiss jewellery house. Inspired by Beauty and the Beast, the Belle Necklace contains an incredible mix of blue sapphires, pink sapphires, amethysts, and diamonds in all sizes and shapes and is finished in 18k white gold. The Belle necklace was created in collar style with filigree work wrapping around the treasure trove of precious gemstones. The centre glory is a flawless 69-carat pear-shaped tanzanite. Valued at over 1 million USD, this necklace is fit for a princess.


The Future of Tanzanite


Tanzanite is a very rare and stunning gemstone. It's only found in one place on Earth, which only holds a limited amount. Unless another mine is located, the cost of Tanzanite will increase as mining activity starts to slow down. Once the Tanzanite mine is depleted, no new Tanzanite material will come into circulation unless a new mine is located. If an alternative mine is not located again, Tanzanite will have run its course, and those fortunate enough to get their hands on one of these high-quality gemstones will be one of the few to hold such a beautiful piece of the Earth.


Browse our regal range of luxurious natural Tanzanite gemstones. Whatever you can dream of, The Sapphire Merchant can make for you. If you fall in love with one of our Tanzanite gemstones and are still determining a design idea, we collaborate with you to create something you will adore for many years to come. Contact The Sapphire Merchant today to start a journey that tells your story with an incredible custom jewellery piece. 





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