Tanzanite

Introduction
Blue lightning
Ever since Ndugu Jumanne Ngoma stumbled upon shimmering blue crystals in the shadows of Tanzania’s Mount Kilimanjaro, tanzanite has become one of the world’s most sought-after gemstones. No wonder. As anyone who has ever laid eyes on this gem can testify, tanzanite has a take on the blues that can drive even the finest sapphire to kick the nearest dog. And yet, when it was first discovered, Ngoma could hardly give it away:
I found the tanzanite in Merelani, Arusha, in the area called Kiteto at the beginning of January 1967. I was on my way to visit some of my relatives who live in Kiteto, when walking through the bush I saw some crystals of a blue mineral lying on the ground. There were very nice… They were blue, some were transparent… In a few hours I collected about 5kg — they were all very lovely blue crystals.
A friend told me to get on the bus and go to Nairobi… where there was a much bigger gem market than in Arusha. So I borrowed some money for the journey and went to an overseas company who deals in precious stones… and I let them see the 5kg of tanzanite. They didn’t even know what the mineral was. They told me, though, that as soon as they knew, they would let me know. I left them with the 5kg of tanzanite in exchange for a return ticket home, worth $5.… 33 years have gone by and I’m still waiting for their answer! But I kept some samples for myself.
Ndugu Jumanne Ngoma, relating his discovery of tanzanite to author Valerio Zancanella
Following this discovery, tanzanite quickly became one of the world’s most popular gemstones. Some credit is due to Tiffany & Co., who introduced it to market with a lovely name that pays tribute to the beauty of the land of its birth. Tiffany understood that to call this glamorous gem by its mineral name, blue zoisite, would not do it justice.

Today tanzanite is available in a variety of shapes and sizes. Rarely pure blue, tanzanite almost always displays overtones of violet. In smaller sizes, it tends toward lighter shades of lavender and periwinkle, while in sizes above ten carats, tanzanite can show richer, more intense blue colors.
Tanzanite is trichroic, meaning it shows different colors when viewed in different directions. One direction is blue, another purple, and the other bronze. When found in the ground, the bronze color often dominates. However, with gentle heating (~520°C), one can watch the blue and violet bloom and deepen in the stone. The resulting color is completely stable.

Legend has it that the effect of heat was first discovered when brown zoisite crystals exposed on the surface were caught in a fire set by lightning that swept across the grass-covered Merelani hills. The Masai herders who drive cattle in the area noticed the beautiful blue color and picked the crystals up, becoming the first tanzanite collectors.
Owing their color to traces of the element vanadium, cut stones with more blue than violet tend to be more expensive because the crystals generally form with the blue color axis oriented along the width of the crystal instead of the length. That means that if the cutter chooses to maximize the purity of the blue color, the stone cut from the rough will be smaller and thus cost more per carat. The blue color, however, is so beautiful that the sacrifice is often worth it.
Rarely, stones of a green color are also found. These are particularly valued by collectors.
Lying in the shadow of Mount Kilimanjaro, the world’s only commercial tanzanite mines have resulted from massive tectonic activity that created one of the most highly mineralized zones in the world — the Mozambique Orogenic Belt.

Tanzania’s gem deposits are a product of this belt, which cuts a 200–300 km-wide north-south swath through the central and eastern part of the country. Running all the way from Mozambique in the south, to the Sudan and Ethiopia in the north, it is home to many of East Africa’s most important colored gemstone finds.
Rocks in this belt underwent several different cycles of tectonism, as well as extensive metamorphism, plutonism, folding and faulting. The metamorphism produced granulite complexes, which, when combined with major crustal movements, formed a witch’s brew of unusual minerals and color varieties. In the granulitic cauldron, pressure and hot fluids cannibalized minerals for their chromophores — vanadium, chromium, manganese — where they were absorbed by existing minerals. At other times, minerals were simply dissolved and built anew. The result is one of the richest gem belts on the planet.

Tanzanite is recovered from pegmatitic veins that have become so stressed they have broken into smaller pieces known as boudins. Gems are found in small pockets within the boudins.
Originally tanzanite could easily be collected on the surface, but this scavenger mining quickly gave way to pits and now tunnels, some of which extend hundreds of meters beneath the surface Working the Blueseam: The Tanzanite Mines of Merelanie
The conquest of the earth, which mostly means the taking it away from those who have a different complexion or slightly flatter noses than ourselves, is not a pretty thing when you look into it too much.
Joseph Conrad, Heart of Darkness
In much of the world, the haves and those not even close toil side-by-side, each with simultaneous desire and disdain for the other. Perhaps nowhere else on the planet are the contrasts as compacted as the few square kilometers that comprise the tanzanite mines of Merelani. This is where First World meets Third, a pressure-cooker that turns brown earth to blue jewels—where envy and avarice squeeze out of the graphite dust that coats all—black, white, and brown—in a sparkling mixture of blood, sweat and indigo tears.

15.42 carats of deep blue wonder. The discovery of gems such as this set the world afire in 1967.
Photo © Wimon Manorotkul/Pala International; specimen courtesy of Robert & Phyllis Hughes
Blue lightning
Ever since Ndugu Jumanne Ngoma stumbled upon shimmering blue crystals in the shadows of Tanzania’s Mount Kilimanjaro, tanzanite has become one of the world’s most sought-after gemstones. No wonder. As anyone who has ever laid eyes on this gem can testify, tanzanite has a take on the blues that can drive even the finest sapphire to kick the nearest dog. And yet, when it was first discovered, Ngoma could hardly give it away:
I found the tanzanite in Merelani, Arusha, in the area called Kiteto at the beginning of January 1967. I was on my way to visit some of my relatives who live in Kiteto, when walking through the bush I saw some crystals of a blue mineral lying on the ground. There were very nice… They were blue, some were transparent… In a few hours I collected about 5kg — they were all very lovely blue crystals.
A friend told me to get on the bus and go to Nairobi… where there was a much bigger gem market than in Arusha. So I borrowed some money for the journey and went to an overseas company who deals in precious stones… and I let them see the 5kg of tanzanite. They didn’t even know what the mineral was. They told me, though, that as soon as they knew, they would let me know. I left them with the 5kg of tanzanite in exchange for a return ticket home, worth $5.… 33 years have gone by and I’m still waiting for their answer! But I kept some samples for myself.
Ndugu Jumanne Ngoma, relating his discovery of tanzanite to author Valerio Zancanella
Following this discovery, tanzanite quickly became one of the world’s most popular gemstones. Some credit is due to Tiffany & Co., who introduced it to market with a lovely name that pays tribute to the beauty of the land of its birth. Tiffany understood that to call this glamorous gem by its mineral name, blue zoisite, would not do it justice.
Today tanzanite is available in a variety of shapes and sizes. Rarely pure blue, tanzanite almost always displays overtones of violet. In smaller sizes, it tends toward lighter shades of lavender and periwinkle, while in sizes above ten carats, tanzanite can show richer, more intense blue colors.
A stunning design from Ginny Dizon, incorporating natural brown and faceted blue tanzanites. A gentle heat treatment turns the brown crystals blue.
Tanzanite Foundation

Tanzanite is trichroic, meaning it shows different colors when viewed in different directions. One direction is blue, another purple, and the other bronze. When found in the ground, the bronze color often dominates. However, with gentle heating (~520°C), one can watch the blue and violet bloom and deepen in the stone. The resulting color is completely stable.
Legend has it that the effect of heat was first discovered when brown zoisite crystals exposed on the surface were caught in a fire set by lightning that swept across the grass-covered Merelani hills. The Masai herders who drive cattle in the area noticed the beautiful blue color and picked the crystals up, becoming the first tanzanite collectors.Owing their color to traces of the element vanadium, cut stones with more blue than violet tend to be more expensive because the crystals generally form with the blue color axis oriented along the width of the crystal instead of the length. That means that if the cutter chooses to maximize the purity of the blue color, the stone cut from the rough will be smaller and thus cost more per carat. The blue color, however, is so beautiful that the sacrifice is often worth it.
Rarely, stones of a green color are also found. These are particularly valued by collectors.
Cauldron of gem creation
Proclus in his book of Sacrifice and Magick, saith, That the antient Priests were wont to mix many things together, because they saw that divers Simples had some property of a God in them, but none of them by it self sufficient to resemble him. Wherfore they did attract the hevenly influences by compounding many things into one, whereby it might resemble that One which is above many.
Lying in the shadow of Mount Kilimanjaro, the world’s only commercial tanzanite mines have resulted from massive tectonic activity that created one of the most highly mineralized zones in the world — the Mozambique Orogenic Belt.
Tanzania’s gem deposits are a product of this belt, which cuts a 200–300 km-wide north-south swath through the central and eastern part of the country. Running all the way from Mozambique in the south, to the Sudan and Ethiopia in the north, it is home to many of East Africa’s most important colored gemstone finds.

Rocks in this belt underwent several different cycles of tectonism, as well as extensive metamorphism, plutonism, folding and faulting. The metamorphism produced granulite complexes, which, when combined with major crustal movements, formed a witch’s brew of unusual minerals and color varieties. In the granulitic cauldron, pressure and hot fluids cannibalized minerals for their chromophores — vanadium, chromium, manganese — where they were absorbed by existing minerals. At other times, minerals were simply dissolved and built anew. The result is one of the richest gem belts on the planet.
Tanzanite is recovered from pegmatitic veins that have become so stressed they have broken into smaller pieces known as boudins. Gems are found in small pockets within the boudins.

Map of Tanzania and southern Kenya, showing the major gem localities. The tanzanite mines of Merelani are located just south of Mt. Kilimanjaro. Click on the map for a larger version. Map © R.W. Hughes
Originally tanzanite could easily be collected on the surface, but this scavenger mining quickly gave way to pits and now tunnels, some of which extend hundreds of meters beneath the surface.
Miners work the face in TanzaniteOne's Block C mine. The extraction process begins with brute force, but ends with the utmost care to avoid damaging the gems. Unlike the other blocks, mining conditions at Block C are excellent and the company has a fine safety record. Photo © TanzaniteOne
TanzaniteOne
I couldn't help asking him once what he meant by coming here at all. 'To make money, of course. What do you think?' he said scornfully.
Joseph Conrad, Heart of Darkness
While Tanzania's tanzanite mines were discovered by a native Tanzanian, the potential wealth quickly attracted outsiders. These included a variety of characters, both Tanzanian and foreign, who pushed the original discoverer out. Soon the Merelani hills were awash with thousands of fortune seekers and chaos ensued. In 1971, the tanzanite mines were nationalized, but production over the next 20 years was erratic, due to haphazard mining and theft. By 1989, an estimated 30,000 artisanal miners were working in the area.
In 1990, the Tanzanian government curbed artisanal mining and demarcated the area into four blocks: A, B, C and D. Block A was awarded to Kilimanjaro Mines Limited, Blocks B and D to small-scale miners and Block C to Graphtan Limited, a graphite mining company. Graphtan ceased mining activities in 1996 and Afgem acquired the mining licence for Block C. In 2000, Afgem completed a feasibility study for the commercial mining of tanzanite and mine development commenced in 2001. In 2004, the TanzaniteOne Group, a publicly-traded company, acquired Afgem's tanzanite business and assets.
Merelani's tanzanite mines lie within a slender strip of ground, just two km deep by eight km wide. This is Tanzania's most important gem mining area, with as many as 70,000 people supported by those mining, cutting and trading tanzanite in Merelani, Arusha and beyond. 5000 to 6000 miners are said to work at Block D alone, which is the area where the deepest tunnels are found, as the deposit trends down from Blocks A through D.
The TanzaniteOne mine is impressive, to say the least. Indeed, the entire operation exudes class, from the mining conditions underground to the promotional efforts of the Tanzanite Foundation, a non-profit dedicated to promoting tanzanite and assisting the people who mine it. Having observed colored gem mining operations around the world, we must say that the rest of the industry has much to learn from their approach. Does this sound like gushing? We hope so, for they have earned it.
And yet TanzaniteOne faces the dilemma that, no matter how much good work they do, no matter how many schools they fund or roads they build, no matter how much they promote tanzanite as a whole, they will always be regarded with suspicion. The locals understand that, like Joseph Conrad's Kurtz in Heart of Darkness, they have come to this land solely to make money. When the profit is gone, they will leave. Native Tanzanians are different. This is their land, their home. Even if the money is gone, they will remain. They have nowhere else to go.
The road to somewhere
Kilimanjaro Airport lies some 50 km from Arusha. A further 16 km along a small dirt road brings you to the world's only significant tanzanite deposit. Whirlwinds swirl lazily on the dusty plain as one heads into the Merelani hills, carrying you straight into the blue heart of tanzanite.
Along the way, a sign reveals: "This road has been proudly built, sponsored and maintained by the Tanzanite Foundation."
As we passed, a local member of our party declared the billboard an insult. "Look at this road," he snorted. "Dirt! With all the money they are making, why isn't it tarmac [paved]?"
Hmmm… We countered that, while it was unpaved, it did happen to be graded and was as good as any unfinished road in the country. Indeed, in the three weeks we had spent traveling around Tanzania, we had seen far worse.
Then a discussion began on the cost of paving roads. We suggested that such pavement was quite expensive, but that if the Tanzanian government felt a paved road in this place was important, they could simply raise the royalties on TanzaniteOne to pay for it. This brought laughs all around; even the original doubting Thomas had to admit that, if the rent were raised, not a single shilling would make its way to Merelani for road improvement.
The conversation was brought to a rapid halt by an incredible thump. We had just turned off the road maintained by the Tanzanite Foundation and were now on the "regular road" to Merelani. These few kilometers were as rough as anything we had suffered in Tanzania.
The blue streets of Merelani
Strength is just an accident arising from the weakness of others.
Joseph Conrad, Heart of Darkness
Driving towards TanzaniteOne's Block C mines, we inquired as to the possibility of visiting Merelani and the other operations; before we could even finish the sentence, a curt "no" was expelled by the company's driver.
Up on the hill, we took up the question with a higher authority, namely TanzaniteOne's Managing Director, Zane Swanepoel. Brows furrowed and, amidst hushed whispers, the possibility was discussed. The question was not so much that of hiding the dark side, but more one of physical safety. Not just ours, but that of the TanzaniteOne staff who might take us into the lion's den. In the end, discretion ruled. We would have to seek an alternative guide to visit Merelani's blue streets and indigo pits.
by Vincent Pardieu and Richard W. Hughes, with Guillaume Soubiraa,
Michael Rogers, Warne and Monte Chitty and Philippe Brunot
Tanzanite was enthusiastically celebrated as "Gemstone of the 20th Century" after its discovery in 1967. It is named after the East African state of Tanzania where its only deposit has been found. The legendary New York jewelers Tiffany & Co were the first to promote tanzanite as a fine gemstone.
Tanzanite is a variety of the zoisite species. In good quality the color is ultramarine to sapphire blue. The most popular color is a saturated blue, which shows a purplish hue shimmering around it.

Tanzanite needs experienced cutters to treat it carefully, as the stone has perfect cleavage in one direction. The stone is cut in all imaginable shapes and forms, from classical round cuts to imaginative designer cuts.
Nearly all tanzanite has been heat treated to produce the striking violet-blue color.

Due to its minor hardness (6.5-7 on Mohs scale) tanzanite is not especially durable. Therefore it should be worn with care.
Tanzanite has become so popular that in October of 2002 the American Gem Trade Association (AGTA) announced that tanzanite had joined zircon and turquoise in the list of birthstones for the month of December.
Tanzanite colors
Buying Tanzanite
Where is Tanzanite found?
Common Tanzanite treatments
World-famous Tanzanite
Tanzanite gemology
Tanzanite legends & lore
Tanzanite colors
In good quality the color is ultramarine to sapphire blue. The most popular color is a saturated blue, which shows a purplish hue shimmering around it.
Buying Tanzanite
Due to its minor hardness (6.5-7 on Mohs scale) tanzanite is not very resistant. Therefore it should be worn with care, and should never be cleaned by ultrasonic methods.
As the stone is found in only one location, it is especially rare.
Color
The most popular color is a saturated blue, which shows a purplish hue shimmering around it.
Lighting
Typical for Tanzanite is the appearance of several colors in one and the same stone (pleochroism), which means, depending on the perspective, the stone appears blue, purple, brown or yellow. In artificial light tanzanite color appears more amethyst blue.
Clarity
Tanzanite is a transparent gem, and eye clean specimens can often be found. Tanzanite cat's eyes are rare.
Cut
Tanzanite needs experienced cutters to treat it carefully, as it has perfect cleavage in one direction. The stone is cut in all imaginable shapes and forms, from classical round cuts to imaginative designer cuts.
Tanzanite location and deposits
The only known deposit of tanzanite is a five square mile hilltop at Merelani Hills near Ausha, ten miles south of the Kilimanjaro International Airport in Tanzania.
Common Tanzanite treatments
Most rough crystals show a large proportion of brownish-yellow tints, which vanish when heated to 752-932 degrees F (400-500 degrees C).
World-famous Tanzanite
Tanzanite gained worldwide fame as a fine and rare gemstone in itself. Tanzanites in especially good qualities and larger sizes are in serious demand and command high prices. It isn't only the spectacular color. Since the stone is found in only one special location in the entire world, it is especially rare.
Tanzanite gemology
Species: Zoisite
Color: Sapphire blue, amethyst, violet
Chemical composition: Ca2Al3(Sio4)3(OH) calcium aluminum silicate
Crystal system: Orthorhombic, multifaceted prisms, mostly striated
Hardness: 6.5-7 (Mohs scale)
Specific gravity: 3.35
Refractive index: 1.691 - 1.700
Birefringence: +0.009
Color of streak: White,
Absorption spectrum: 595, 528, 455
Fluorescence: None
The Tanzanite zodiac, myth & legend
Too new to have written a page for itself in the books of myth, history, wisdom, the zodiac scheme or the relation between planets and mankind, tanzanite left its mark in present time. It has become so popular that in October of 2002 the American Gem Trade Association (AGTA) announced that tanzanite had joined zircon and turquoise in the list of birthstones for the month of December.