SCI Style Trends – Tanzanite, Portrait of a Serial Thriller

Three different views of tanzanite rough showing the three pleochroic colors when isolated through a polarizing lens. Photograph courtesy of The Tanzanite Foundation
Three different views of tanzanite rough showing the three pleochroic colors when isolated through a polarizing lens.
Photograph courtesy of The Tanzanite Foundation

In July, 1967, in the grassy hills of Merelani, or Mererani, in the Manyara Region of northern Tanzania, a Maasai tribesman prospecting for gold happened upon transparent crystals of intense bluish-purple color laid bare by weathering and glistening in the sunlight. Unfortunately, our finder’s name remains inconclusive.

At the time, it was first speculated that the crystals might be peridot, or olivine. Upon closer examination they appear to be dumortierite. Then again, they might be cordierite, also known as iolite. Finally, it is suggested that they are blue sapphire.

Ultimately, none of the local geologists and gemologists had the necessary resources on hand to make a conclusive identification, so parts of the specimen were sent abroad. The Gemological Institute of America (GIA) made a conclusive identification, finding the specimen to be a blue variety of zoisite. This identification was soon confirmed by other laboratories around the world.

The stuff dreams are made of: this finely cut Tanzanite octagon shows off an exceptionally fine color. Note how the pleochroism appears to cause the color to shift as your eye scans across the stone. Photograph courtesy of The Tanzanite Foundation
The stuff dreams are made of: this finely cut Tanzanite octagon shows off an exceptionally fine color. Note how the pleochroism appears to cause the color to shift as your eye scans across the stone.
Photograph courtesy of The Tanzanite Foundation

Until now, zoisite has led the life of an outsider and not a mainstream gem, occurring in a variety of different colors in random places like Kenya, Norway, Switzerland, Austria, India and Pakistan besides Tanzania.

But then there is that hauntingly intense color…

No variety of zoisite offers such an amazing sensation of color as the blue one, and people sensitive to color find the experience particularly dramatic and rewarding. The source of the magic is zoisite’s pleochriosm (see sidebar), and color in blue zoisite is a particularly subtle and mysterious kind of moving target, which brings us to something of a creation myth.

When blue zoisite is mined, it is usually a nondescript blend of brown, blue and violet. For the material to attain its amazing color, it needs to be exposed to heat. It has been found that heating blue zoisite to around 715° F (390° C) for half an hour will cause trace inclusions of vanadium and titanium to change their oxidation levels in such a favorable way that the bodycolor shifts toward intense blue and purple, leaving the brown behind.

When there is too much heat, or when the heating goes on for too long, stones disintegrate. Strongly included stones are less likely to withstand the heating process. By definition, inclusions are foreign

The Mawenzi, named after the second highest of Kilimanjaro's three peaks, was pulled from a depth of 885 ft. (270 m) in 2005 and is the largest Tanzanite gem quality crystal on record. It measured 8.6 X 3.1 X 2.7 ins. (220 by 80 by 70 mm) and weighed 7.4 lbs (3.368 kg, or 16,839 ct.). Note the color of this unheated piece of rough. Photograph courtesy of Tanzanite One
The Mawenzi, named after the second highest of Kilimanjaro’s three peaks, was pulled from a depth of 885 ft. (270 m) in 2005 and is the largest Tanzanite gem quality crystal on record. It measured 8.6 X 3.1 X 2.7 ins. (220 by 80 by 70 mm) and weighed 7.4 lbs (3.368 kg, or 16,839 ct.). Note the color of this unheated piece of rough.
Photograph courtesy of Tanzanite One

objects and therefore have a different thermal coefficient of expansion. They are quite likely to fracture the host with heating. As a result, heavily included specimens eliminate themselves during the heat treatment required to make blue zoisite salable. As a result, you can expect the surviving stones to be lightly included, if at all, with many gems being eye-clean.

So how did our Maasai tribesman come across the vivid blue crystals described earlier? The official explanation is that the crystals must have indeed been heated, either during a geological event sometime earlier, or, more likely, a wildfire caused by one of the lightning storms that sometimes occur in that area. Over what has been found to be upward of 550 million years of age for blue zoisite, either appears to be a reasonable assumption.

Barely a year passed after the unearthing of the Merelani crystals, and they made an impression with upper management at Tiffany &

For designer Cynthia Renée there was no question that this Tanzanite would command the stage entirely on its own in the exquisitely hand-fabricated basket setting by goldsmith Mirjam Butz-Brown. Photograph by Ken Mogadham
For designer Cynthia Renée there was no question that this Tanzanite would command the stage entirely on its own in the exquisitely hand-fabricated basket setting by goldsmith Mirjam Butz-Brown.
Photograph by Ken Mogadham

Co. The New York-based jeweler, who pays at least as much attention to the art of marketing as to creating jewelry, was so taken by the gem that a campaign was launched in which the name “Tanzanite” replaced the scientifically correct, but clearly less romantic “blue zoisite.” Officially, it had been dreamed up in honor of the country of origin, Tanzania.

All the fine packaging paid off, and Tanzanite was well on its way, thrilling jewelry consumers across Europe, where colored stones already enjoyed an acceptance on par with diamonds. In the US, Tanzanite’s rise was more dramatic, as there was little in terms of colored stones besides the Big Three.

As Hayley Henning, Executive Director Tanzanite Foundation, puts it, “Tanzanite is one of the most extraordinary gem discoveries in recent history, and because of its single source, limited supply and stunning color, has it’s own very distinct place in the world of colored stones. Designers around the world are mystified by Tanzanite’s beauty and brilliance, and are creating magnificent jewels that will be passed down from generation to generation, when Tanzanite will no longer be so freely available.”

As Tanzanite caused jewelers and their customers alike to rethink their position on color, it prepared fertile ground for other colored stones, some of which had a long history and others, like Tsavorite, whose time was yet to come. Being the beginning of a fundamental change in the appreciation for colored stones in the US brought

Pendant and ring created by Ilka Bahn. The combination of Tanzanite and pink tourmaline make for an intense color composition that might be overpowering were it not for the colorless diamonds. Photograph by Mia Dixon/www.palagems.com
Pendant and ring created by Ilka Bahn. The combination of Tanzanite and pink tourmaline make for an intense color composition that might be overpowering were it not for the colorless diamonds.
Photograph by Mia Dixon/www.palagems.com

forth an entirely new generation of cutters, carvers and lapidaries who were less interested in perpetuating convention than creating their own unusual and inspiring fancy cuts and gem carvings. In response to these rapid and fundamental developments, the American Gem Trade Association (AGTA) was created in 1981. Its mission: to establish ethical standards, educate and protect consumers. In 2002 the AGTA officially anointed Tanzanite birthstone for the month of December, the first update of the birthstone list in nine decades.

Meanwhile, back in Merelani, operations big and small began to stake claims while the speculative rumors about sapphire were still running amok. As is the case when a novel gem production area comes online, there was a lot for all the players to learn in terms of legal matters and government control infrastructure, sustainability and socio-economic issues.

All indications were that the hills of Merelani would remain the sole producing area for Tanzanite, and in 1990 the Tanzanian government decided to divide the mining area into four blocks: two for numerous smaller operations, the other two for an individual larger one.

Marketers quickly seized on the fact that this was the only area on earth that produced Tanzanite, measuring a mere 1 ¼ by 3 miles. The idea that Tanzanite was “at least 1,000 times rarer than diamond” resounded so positively that surface deposits were soon depleted. As miners began to push underground, their cost went up and per carat prices adjusted accordingly.

Good Friday of 1998, disaster struck. Torrential rains softened the ground to the point where the many interconnected shafts flooded, collapsing entirely in one of the blocks, burying more than 100 miners alive. While the tragedy didn’t make public headlines, the jewelry trade was stunned.

Adding insult to injury, the subsequent impasse in supply caused a further price increase. The affected mine shafts were eventually restored, but prices remained strong when production picked up because the mining disaster resulted in tighter safety regulations, and mining operations faced higher costs.

Since there had been no gem cutting industry to process early production of Tanzanite, the majority of rough went to the colored stone cutting center of Jaipur, the capital of the Indian state of Rajasthan. Realizing that cutting abroad meant a loss of revenue, Tanzania’s parliament passed the 2010 Mining Act. The aim was to provide Tanzanian private-sector operations and individuals with better access to funding, and establish a domestic lapidary industry while improving workers’ safety and environmentally sustainable practices.

Although there are several grading systems for Tanzanite, the overriding principle with colored stones is the gem material’s bodycolor. The most desirable bodycolor range for Tanzanite is pure blue to violet blue, and the more saturated, the better.

Pleochroism in Tanzanite has a way of throwing inexperienced gemologists off, so if you find yourself in the market for a substantial stone, you want to be sure you are dealing with someone who is more jaded. Cut and clarity are also factors of importance, although they are not considered as important as color. A well-executed cut is the precondition for unleashing everything a gem’s bodycolor has to offer and may be even more important than clarity. In the case of Tanzanite, the heavier included stones rarely survive the heating process, making clarity something of a lesser consideration.

Tanzanite is not a hard stone. To put it in perspective, Tanzanite is softer than quartz and can be scratched with a hard steel point. It is also quite brittle and has one direction where the atoms are spaced particularly far apart, resulting in weaker atomic bonding. This direction of structural frailty is called perfect cleavage. It won’t require a strong rap down that direction to split a stone clean in two. Another weak spot of Tanzanite is its aversion to thermal shock: a stone can fracture if taken from a hot pool and immersed immediately a cold water.

These physical properties limit your options in wear and in maintenance. You will definitely never want to expose Tanzanite to the shockwaves of an ultrasonic cleaner, especially not if it is the heated kind, and then rinse in cold water or blow it clean with a steam jet. A gentle brushing with a soft toothbrush with dish detergent in a bowl of lukewarm water and rinsing in lukewarm water (as described in detail in the November 2013 edition of Safari Magazine) is the best you can do for your Tanzanite treasure to keep it looking and performing its best.

With these characteristics in mind, you also want to consider your options when it comes to your choice of Tanzanite jewelry items. Rings and bracelets frequently are subjected to mechanical shock–on occasion severely so. There are other stones that stand up better to the rigors of everyday wear over the lifetime of a ring or a bracelet. People tend to be more careful with evening rings, and setting a Tanzanite in an evening ring could be considered a calculated risk.

Tanzanite is best worn in jewelry items that are less exposed, like pendants, earrings and necklaces. The intense color of a fine Tanzanite has a way of taking up a lot of visual space, not only in the jewelry piece, but also on the wearer in general. Giving it that amount of territory will likely make a stunning statement.

Bill Larson, President of Pala International in Fallbrook, California, points out that, “Tanzanite is an exciting stone, because it was only discovered in 1967, so all the mythology on this gemstone is what we’ve seen created over the past 40 years or so. A fairly unique situation.”

And what about the future of prices? Due to depletion, mine shafts are currently reaching 2,300 feet and, as long as there is no alternative for Tanzanite production to the Merelani area, it is safe to assume the prices will increase before they go down, since Tanzanite is one of the most coveted gems today and becoming rarer.– Robert Ackermann, G.G.

Leave a Reply