Tanzanite Is Africa's Real Blue Diamond

By: Carrie Whitney, Ph.D. & Austin Henderson  | 
Cut and polished tanzanite stones are extremely rare — even more so than diamonds. Patrick AVENTURIER/Gamma-Rapho via Getty Images

If rarity boosts a gemstone's value, tanzanite, which is mined from just one source, could be prized for that fact alone. Miners extract all the world's tanzanite from an 8-square-mile (20-square-kilometer) area near Mount Kilimanjaro in Tanzania. In contrast, people find diamonds, also seen as rare, in over 30 countries across multiple continents.

Recognizable for its vibrant bluish violet color, the tanzanite gemstone owes its place among today's favorite gemstones not only to its recent discovery, but also to a modern publicity campaign that catapulted the gem to fame.


What Is Tanzanite?

Tanzanite is a variety of the species zoisite. In gemology, according to Brenda Harwick, senior manager of gemology instruction at the Gemological Institute of America (GIA), stones classify into species and varieties.

A gemstone has a distinct chemical composition and is both natural and inorganic. In the case of tanzanite, that composition includes calcium, aluminum, silica oxide and hydroxide. In other words, it's a calcium aluminum hydroxy silicate.


What's more important (anywhere but chemistry class) is that tanzanite boasts two important gemstone qualities: beauty and rarity. A gemstone's value often lies in its scarcity, meaning it isn't found everywhere on Earth, Harwick points out. It requires certain geological events in order to form.

"Nature is interesting, and it really is unique when gemstones form because it does involve having the right temperature, the right pressure and the right chemical composition," she says. "And that is part of its allure."

On the Mohs Hardness Scale, tanzanite falls in the 6 to 7 range, which makes it easier to scratch than diamonds (10), rubies and sapphires (9), or even quartz (7). With its softer nature and fair-to-poor toughness ranking, tanzanite is one of the more delicate gemstones. It's also sensitive to thermal shock, aka sudden temperature changes.

tanzanite stones
Most tanzanite does not display its vibrant color when initially mined. As much as 95 percent of the gems are heat-treated to achieve the blue color.


Where Is Tanzanite Found?

Tanzanite is found in only one place on Earth: Tanzania. Although it's not as expensive as a diamond, this blue zoisite is much rarer. In fact, some estimates have tanzanite at 1,000 times rarer than diamonds.

It may be hundreds of millions of years old, but the rare gem was first brought to the attention of humans in 1967, according to the website for Cape Town-New York jeweler Shimansky.


The story goes that tanzanite was first discovered either by a Masai tribesman (the Masai are an ethnic group living in northern, central and southern Kenya and northern Tanzania) who first noticed the bright blue crystals and contacted Manuel de Souza, an Indian tailor and prospector, or else de Souza himself discovered it.

Either way, with hope that the colorful deposit was sapphire, de Souza made a mining claim to the area. Although zoisite, the species of which tanzanite is a variety, was already known, it was typically translucent, opaque, green and used for carving jewelry, according to Harwick. Tanzanite's brilliant color was an exciting find.

Harry Platt, the erstwhile chairman of Tiffany & Co., played a pivotal role in unveiling this blue marvel to the world. Platt spotted it while visiting a lapidary in Europe and not only gained the rights to sell the stone, but also got to name it, which he did in honor of its native land. More than five decades later, the Mount Kilimanjaro source near Arusha, Tanzania, is still the only place in the world to source the gem.

tanzanite mine
Tanzanite mines can only be found in one place on Earth: Tanzania. This mine shaft is 3,280 feet (999.7 meters) deep and accessible only via a wooden ladder.
Patrick AVENTURIER/Gamma-Rapho via Getty Images


What Does Tanzanite Look Like?

Tanzanite captivates with its pure blue or blue-violet color, which is similar to sapphire. It is color, after all, that sells colored stones, Harwick says. So better stones have more intense color and will weigh 5 carats or more. The bigger the stone and the more intense the color, the better the value.

Interestingly, most tanzanite does not display its vibrant color when mined. As much as 95 percent of the gems mined are heat-treated to achieve the blue color. Most untreated tanzanite comes out of the Earth with a brownish hue. Once heated to a brilliant blue, tanzanite's color is stable, so buyers do not need to worry that it will fade.


The gem's final hue can vary based on its cut, potentially veering towards gray or purple shades, which might decrease its value. Lighter colored stones indicate lower gem quality. Additional varieties of zoisite include thulite (pink) and anyolite (red/ruby), and it can also show up as other colors like greenish or yellow.

How Does Tanzanite's Value Compare to Other Gems'?

Although tanzanite is rarer than both diamonds and sapphire, it commands a lower price on the market. One reason might be the durability factor; tanzanite is only "reasonably durable," while sapphires are second only to diamonds in durability, according to Angara.com.

While a sapphire might range from $800 to $1,200 per carat, tanzanite can be had for just $300 to $425 per carat, making it a cost-effective substitute for sapphire, depending on the application.


For instance, violet-blue tanzanite rings may be visually stunning, but the gems would be more prone to damage because of their relative softness and how much we use our hands. But tanzanite earrings, or a tanzanite pendant on a necklace? Simply dazzling.

To put all of these gems in perspective, diamonds start at around $3,080 per carat and can increase in value significantly from there. Of course, value changes with supply and demand, so prices fluctuate.

tanzanite jewelry
Tanzanite jewelry became popular in the late '60s when Tiffany & Co. began offering it in its stores. It's best in special occasion pieces because it's a softer stone.
NIKLAS HALLEN/AFP via Getty Images


How Is Tanzanite Used Today?

Like many gems, tanzanite does not have any specific industrial value, but it has an important place in the jewelry industry. There aren't many naturally blue stones, especially with such vibrant color, and tanzanite does not have a synthetic counterpart.

Some people consider gemstones to have healing or spiritual purpose. Certainly, ancient peoples had specific beliefs about them and uses for them. But we can't delve too far into the history of tanzanite because it was so recently discovered.


When it burst on the jewelry scene in 1968, tanzanite changed the direction of Tiffany & Co.'s style from "simple gold jewelry to colorful designs with large stones," Melanie Abrams wrote for The New York Times in 2018.

Because of its less durable nature, tanzanite works well in special occasion jewelry or items that like necklaces and earrings.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.


Frequently Answered Questions

Why is tanzanite stone expensive?
Tanzanite is expensive because it is a relatively rare gemstone, found in only one place in the world (Tanzania) and not easy to mine.