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Roger Weller, geology instructor

by Miguel Wachtel
Physical Geology
Fall 2017
Untapped Potential: The Tanzanite

Tanzanites are among the most stunning and rare gems in the world, yet there is still a chance you may never see one in your lifetime.  This is due to their limited availability in the market, which unfortunately, is only becoming more restricted as years pass.  While it is still possible to obtain a high-quality tanzanite, the cost of the gem has skyrocketed as the supply has plummeted.


A tanzanite’s official name is a blue zoisite.  It was named this because of its rich color, which range from a light purple to a deep blue.  Shockingly, tanzanites are not naturally in the blue/purple color range, but instead a brownish color.  When tanzanites are mined, they are a brown color. After its discovery, scientists began to test if there was any way to alter or enhance the gemstone to increase its value.  After multiple experiments, it was found that heat treating the stone to 600 degrees Celsius (1,112 degrees Fahrenheit) for 30 minutes, the oxidation process would occur, causing the blue color to become more profound and enriched, thus increasing the value to the comparatively unappealing brown tanzanite (“Tanzanite”). Since tanzanites started being heat treated, it is difficult to find an untreated brown tanzanite.  This is because whenever one is mined it is almost immediately treated to drastically enhance its value. As heat treatment has become the standard for blue zoisite’s even searching the web for an untreated tanzanite, results in images of a blue colored gem.



Discovery of a Gem

As mentioned earlier, the accessibility of tanzanite is decreasing, and part of the reasoning behind this is because it is only mined in one part of the world.  The world’s only known deposit area is in the country of Tanzania, more specifically in the Merelani Hills (“Tanzanite”).  The size of the mine in its entirety is roughly eight square miles, inherently causing there to be a limited amount of mining that can be done. With the available area that can be mined, it has become more and more costly and time consuming to continue searching and digging for the buried gem.

            The blue-violet crystal was first discovered by a local Tanzanian tribesman by the name of Ali Juuyawatu during the late 1960’s (“Tanzanite”).  Interestingly enough, he was not actively searching for the gem, but happened to stumble upon the tanzanite mine in  the Merelani Hills. However, originally the gem was mistaken for a sapphire.  Juuyawatu had only ever seen a gem with a similar appearance (the sapphire), but this new gem caught his eye because of its vibrancy.

After Juuyawatu’s discovery of the tanzanite, the world eyes shifted towards the previously unrecognized country of Tanzania.  Almost overnight, Tanzania’s crystal became international news, and it was not until 1968 the gem was nicknamed the ‘tanzanite’.  This name was coined by the famed jeweler Tiffany and Company, which decided on the name to commemorate its country of origin (“Tanzanite’s Discovery and History”).  After naming the gem, the high-end jeweler began marketing the tanzanite as one of the most stunning minerals in the world, declaring the tanzanite to be “the most beautiful stone to be discovered in 2,000 years”, and that it could only be found in two places in the world, “…in Tanzania and at Tiffany’s” (“Tanzanite’s Discovery and History).  This promotional technique resulted in a worldwide popularity of the gemstone, thus beginning the ever-lasting demand for tanzanite’s.


Tanzanian Mine Collapse

Unfortunately, due to the high value and scarcity of gems and minerals in Tanzania, companies and individuals have decided to take mining into their own hands in an effort to turn a profit.  These actions had detrimental results, and one tragic example occurred earlier this year.  In February, at least 18 miners became trapped while digging illegally for gold in the town of Buhemba, located in northern Tanzania (“Two killed, several missing in Tanzania mine collapse”).  After some time, emergency services were able to rescue most of the miners, but two were crushed by the falling debris when the mine collapsed, killing them.  These miners were not mining on behalf of any official organization; therefore they did not have proper equipment or clearance codes to be mining in the area.  The collapsing of mine shafts is quite frequent in Tanzania, as smugglers continue to illegally extract gems.  This tragedy ended up having international implications, as the country’s president, John Magufuli, decided to take precautions to make it more difficult for importers to obtain minerals in his country.  By making it more difficult to obtain Tanzanian minerals, Magufuli hoped to discourage illegal miners.  To accomplish his goal, Magufuli passed new bills into the government that increased the royalties tax on gold, tanzanites, and other minerals that were being mined and exported out of the country (“Tanzania’s president signs new mining bills into law”).  In passing these bills, President Magufuli has drastically sent shock-waves throughout the mining industry.  With a higher tax, the Tanzanian government is able to collect more money and thus distribute more to its people.  On the flip side, a higher tax also distresses foreign traders from conducting business with Tanzania, due to the high wholesale costs to them, creating a rippling effect all the way down to the consumer who must pay extra to help the reseller break even on goods.


Illegal Smuggling in Tanzania

Beyond Magufuli’s laws, the Tanzanian Government, in an effort to stop smuggling, has responded by producing certificates of authenticity for their gems. These certificates of authenticity were created to force importers and exported to operate via legal channels if they wanted to have legitimate tanzanites.  Unfortunately for the government, the main importers of tanzanite (such as the United States and India) refuse to legitimize these certificates as official documents, allowing for smugglers to continue selling tanzanite’s without any proof of authenticity (“Tanzanite: how Tanzania can profit from mining its rare stone”). Without the international mining community accepting Tanzania certificates, there is no way to track or control who is mining and selling minerals in their country.


Value of Tanzanites

            As with most gems, the value of a tanzanite is based almost completely on the quality of the stone.  For instance, if a tanzanite has a noticeably brown coloration to it, it will be worth much less than its rich-colored blue counterpart.  A tanzanite of good color, clarity, and depth of color is worth approximately $425 per carat if you were to try and buy one today (“Carat Weight-Tanzanite Prices Per Carat (2016-2017)”).  The value of the gem fluctuates up and down quite often, mostly due to the constant struggle of supply and demand amongst the dealers.  Unlike the market that exists for minerals such as diamonds, the laws of supply and demand completely control the tanzanite industry.  Without any way to regulate the import and export of tanzanite’s there is no possible way to set up an official system to control the prices of tanzanites.

            One similarity that tanzanites have to diamonds is the symbol of elegance they represent. Tanzanites of incredible color and clarity are considered upper-class jewelry, with many being set in gold, surrounded by smaller diamonds to compliment the stone. The following image illustrates one such case of a beautifully colored tanzanite being set in a stunning ring.  As you will notice, the tanzanite set in the ring a deep blue/purple color. These colored tanzanites are the most valuable because of their aesthetic appeal.  A good rule of thumb is the darker the tanzanite, the greater the value (in most instances).

Caring for the Gem

            In conclusion, if you own a tanzanite whether set in a piece of jewelry or not, it is of the upmost importance to make sure you are caring and cleaning for the gem appropriately.  First and foremost, the best way to clean a tanzanite that has become foggy or less vibrant is to soak it in room temperature water containing a neutral soap.  Once it has soaked for a short amount of time, wipe it clean with a dry, soft cloth (“Tanzanite Care”).  The one thing that should not be done to the stone is steam cleaning, as the acids (such as hydrochloric acids) in the cleaner easily cling on and attack the tanzanite, causing the mineral to break down with irreparable damage.  Finally, to minimize the risk of damage, it is not recommended to wear tanzanite jewelry every day, but instead on special occasions. This will give you a better chance of preserving the stone instead of scratching or chipping it from accidentally bumping it on tables, furniture, etc. A tanzanite is a 6.5 to 7 on the Moh’s Scale of Hardness, meaning that although tough, it is not invincible (“Tanzanite Hardness and Durability”). If you are careless with this gem, it can be shattered relatively easily.

            As has been shown, tanzanite’s are among the most beautiful and rare gems in the world. The history of the tanzanite is complex, with the future of the mineral being unknown. There is an evident untapped potential that the tanzanite possesses, and with time I believe we will find a way to make them more commercially available.

            If ever given the opportunity to own a tanzanite, appreciate the time and effort taken to mine and transport the gemstone, as you will never look at the blue zoisite the same again.





Works Cited

Image Citations:

All Images credited to R.Weller/Cochise College:


In-Text Citations:

            Dodgson, Lindsay. “Tanzanite: how Tanzania can profit from mining its rare stone.” Mining Technology, Mining Technology, 26 Apr. 2016,

King, Hobart M. “Tanzanite.” Geology,

Moriarty, Eff. “Tanzanite Price & Tanzanite Value (2016-2017).” Tanzanite Jewelry Designs, Tanzanite Jewelry Designs,

Ng'wanakilala, Fumbuka, et al. “Tanzania's president signs new mining bills into law.” Reuters, Thomson Reuters, 10 July 2017,

rings., Tanzanite Gemstones and tanzanite. “Tanzanite Loose Gemstones, Ruby, Sapphire & More.” Tanzanite Hardness & Durability : Tanzanite Loose Gemstones & Tanzanite Rings | eTanzanite.Com, ETanzanite,

Salaam, Dar E. “Two killed, several missing in Tanzania mine collapse.” News24, News 24, 17 Feb. 2017,


Works Cited

“Carat Weight-Tanzanite Prices Per Carat (2016-2017)”.Tanzanites Discovery & History | Richland Gemstones,