pierre precieuse

Tanzanite: parcours d’une pierre precieuse – French documentary by Mandjou (RFI).

“Pierre precieuse aux reflets bleus, pourpre et bronze, la Tanzanite a ete decouverte dans les annees 60 au pied du Kilimandjaro. Elle est aujourd’hui taillee et polie en Inde… c’ est une entreprise sud africaine qui en a le quasi monopole de la distribution…. Et, 80 % de la production est vendue par les bijoutiers americains…” Le marche de la Tanzanite a travers le monde, reportage de Corinne Mandjou.


Cliquez sur le lien suivant pour écouter le reportage de Corinne Mandjou, journaliste à RFI. Ce reportage, effectué en Tanzanie, retrace l’histoire de la pierre ainsi que son marché actuel.

By late 1967, Manuel de Souza, the discoverer of the tanzanite deposit knew that his initial identification as the mineral olivine (peridot) was incorrect but “dumortierite”, his second guess was also wrong. The correct identification of the mineral as “zoisite” was made shortly after by Ian McCloud, a Tanzanian government geologist in Dodoma, at Harvard and at the University of Heidelberg.

Tanzanite – July 7, 1967: Tanzanite: something new out of Africa

Tanzanite – July 7, 1967: Tanzanite: something new out of Africa… but no one knew what it was…

Few travelers arrive in Tanzania without having heard the magic word “TANZANITE”. It’s a one-of-a-kind gemstone found in the Massai country of Tanzania, right in sight of Mount Kilimanjaro. By nature, tanzanite is trichroic, meaning that it shows different colors, depending on the direction in which it is viewed. The most common natural colors are blue, violet and salmon, caused by traces of the element vanadium in the crystal structure, but other colors do occur in odd corners of the deposit where traces of other metals may partly replace the vanadium.

Most tanzanite is heated before it reaches the market. This worthwhile procedure is entirely legitimate, and was begun by the first generation of tanzanite miners who put their stones into charcoal fires in order to improve their color. The effect is to turn the “salmon axis” to blue/purple without affecting the other two axes. (“Salmon axis” has been put in quote marks here because it is actually commonly colored pink, grey, yellow or otherwise with the “salmon” aspect left to the viewer’s imagination.)

Tanzanite is a variety of the mineral zoisite, named after Siegmund Zois, Baron von Edelstein (1747-1819), an Austrian scholar who financed mineral-collecting expeditions. Within a year or two of Manuel de Souza’s initial discovery in Tanzania, Tiffanys came up with the name “Tanzanite”. In those days, a new name was badly needed for it was a period during which German and Swiss gemstone dealers were very active in East Africa and they claimed that a new name was required because the German pronunciation of the “zoisite” sounded much like the English “suicide”. The truth of the matter is actually far more interesting and goes back to the initial discovery of the tanzanite deposit by Manuel de Souza.

By late 1967, Manuel de Souza, the discoverer of the tanzanite deposit knew that his initial identification as the mineral olivine (peridot) was incorrect but “dumortierite”, his second guess was also wrong. The correct identification of the mineral as “zoisite” was made shortly after by Ian McCloud, a Tanzanian government geologist in Dodoma, at Harvard and at the University of Heidelberg.

De Souza was a tailor in Arusha whose family originated from Goa, formerly part of Portuguese India. In Tanzania, he earned his living by making uniforms for the army but he had the “prospecting bug” and all his spare time and money were spent in looking for minerals. His passion probably started with gold-panning in western Tanzania, but in short order he realized what all East African prospectors come to understand, namely, that the countryside hides a rich and unexpected stock of mineral wealth. Gold is not all that to be found. There are many surprises and the biggest occurred when de Souza discovered what was to become the world’s only tanzanite mining region.

A problem which caused much confusion but little harm was that Manuel had no idea what it was that he had discovered. Further, “zoisite” was the very last mineral name that would have come to mind because of the widespread belief in East Africa that zoisite had to be bright green as at Longido, somewhat further to the north in Tanzania. In truth, zoisite is usually gray, dirty white or dull greenish or brown… “rock colored”. But in Tanzania, a bright green non-gem (opaque) variety with traces of chromium was known far and wide. (In Lexviken, Norway, by contrast, where a non-gem variety colored by traces of manganese is known, people are likely to associate zoisite with the color pink, “manganese pink”.)

But Manuel and his family found themselves with a splendid blue-purple-“salmon” colored transparent gemstone. What was it? The question was important to him because he had to register his mining claim at the government Mines & Geology Department and to do so, he needed a mineral name, even a provisional name. In short order, he came up with the incorrect identification “olivine” and as other prospectors pegged the surrounding countryside around his original discovery site, they came up with other incorrect names “cordierite”, “epidote”, “dumortierite”, etc. Not long afterwards one of the Tanzanian government geologists came up with the correct identification of “zoisite”, though many people continued to harbor doubts until confirmations cam in from Harvard, the British Museum and Heidelberg.

Thus it came about that other people had registered mining claims for the mineral “zoisite” before Manuel de Souza himself got around to changing the name on his original claim registration. During this period another name became popular, a lovely name whose disappearance we regret. This was “Skaiblu”, a Swahili-language borrowing of the English “Sky Blue”.

Zoisite, Tanzanite or Skaiblu, this is a lovely stone.

spessartite

A new spessartite discovery by the Serengeti

In October 2007, my brother Mark called while I was travelling in Europe to let me know he suspected that Tanzania was unveiling yet another gem deposit. “I think we’re on top of something big again. An important spessartite discovery seems to have taken place in the northern part of the country”. His call came right after a few Maasai herdsmen had popped by our Arusha office. But their information was vague and needed to be confirmed…

Confirmation came quickly. The new spessartites came from Loliondo, close to Serengeti National Park and only 7 kilometers away from the Kenyan border. A few years ago, aquamarines had been found and briefly mined in that area.

Rough spessartite garnet

Mark had spent ten exhausting days in the bush in August purchasing what is now believed to be the most important spinel discovery recorded. At that time he had imagined he would be gone a couple of days and had packed a small bag accordingly. Instead he had ended up spending ten days purchasing spinel in Mahenge area. And here we were again. But before we could really think about organizing a new buying trip, the staircase of our office building filled up with Maasai waiting to show us their spessartite garnets. These men had left their cattle at the village in order to rush to the new find. News can travel very quickly in Maasailand… Not one of these Maasai had ever heard of spessartite prior to the discovery. Most had never even handled a gem before. Mark rapidly identified the stones and told the first Maasai that these orange gems were spessartite garnets. Within hours, Maasai were pouring into our office trying to sell their “special types”, “space types”, “spacetites”, “spestites”…

A 12 cts cut spessartite garnet. One of the first spessartites to have been cut from this discovery

As had been the case with the spinel discovery, the spessartites attracted amateur prospectors from all over. Much to our amusement, one of our former watchmen, a Maasai himself, walked into our office one day with a bag full of various sized spessartites. He and plenty of other self-appointed brokers have no experience. Nice clean gems are often mixed with poorly crystallized or unclean material. Prices often need some adjustment…

A spessartite crystal weighing a bit under a kilogram... Spessartite crystals of more than a kilo have been found

Generally speaking, the colors of the Loliondo spessartites are very lively. They are as nice as the Nigerian material. Big pieces are rare, especially the clean ones. A very large proportion (99%) of these spessartites are included and are perfect material for bead or cabochon.

 

gemstone

The first gemstone discovered in East Africa

Those who have read Out of Africa or An Ice Cream War, or remember Bogart in The African Queen, will know that “The Great War” was also fought in Africa. But they are unlikely to have heard of the Battle of Merkerstein, a minor skirmish in the northern part of Tanzania, which was then part of German East Africa (Deutsch-Ostafrika). It was there and then, at Merkerstein around the turn of the year 1914/1915, that the first deposit of gemstones was found in East Africa. A soldier who presumably had other things on his mind saw a bright red stone, a ruby. Was he British or German? Usually it’s said to have been a German but it can depend on who tells the story.

Merkerstein Hill took its name from Moritz Merker (1867-1908), a fine scholar who was also the pre-War German military commander for the Kilimanjaro region. A few crumbling labels in European museums show the name “Merkerstein” even today, but the deposit has long been known as the Longido Ruby Mine, “Longido” being the Masai name of a prominent mountain familiar to those who have driven from Nairobi down to the game parks of northern Tanzania. With time, Merkerstein, Merker, and his never-translated Die Masai (1904) have been generally forgotten, perhaps because Germany was forced to give up its colonies following World War I, but perhaps, too, because of the eerie parallels Merker drew between the ways of the Masai and those of nomadic peoples in the Old Testament.

gemstone

The war story was became widely known, and rubies at “Merkerstein” were said to have been seen again by employees of the Commonwealth War Graves Commission, but the change of administrations from German to British, the Great Depression, a gold rush far to the west, near Lake Victoria, and World War II intervened and it was not until sometime around 1949 that the deposit was re-found. According to one account, a Nairobi-based gold prospector named Tom Blevins and an associate discovered a narrow rock outcrop the length of a football field composed of bright green rock with lovely bright-red six-sided crystals standing out from the surface. “Sacksfull” of loose rubies which had weathered out of the hard green host rock were collected and the two gold prospectors returned to Nairobi, thinking of themselves as rich men. Then, by means of what might charitably be called “lapidary experimentation”, Blevins reduced most of the stones they had collected to tiny valueless fragments. Returning to the deposit, the two men learned that the rubies which remained were for the most part so firmly encased in their matrix rock that they could not be removed without breaking.

But there is also very different version of the rediscovery in which a professional hunter named Louis “Woody” Woodruff accidentally came across a circle of five or six geometrically constructed stacks of the green host rock sitting on the ground, as though waiting for transport that had never come. The Longido property then passed through a series of owners and managers, including the Polish Prince Eustache Sapieha, a greatly liked figure on “the Nairobi scene”, who in later years had a little chapel built on his property with a footpath to it paved with ruby shards splashed with green. Prince Sapieha, universally known as “Stash”, had come to Kenya in 1948 after the Communist takeover of his country, joining other members of his family and the sizable Polish-Kenyan community which had coalesced in the years following the Nazis invasion in 1939. Stash, who had seen the stacks of rock, thought that no one but an army would have done things that neatly.

Stash and his wife and three daughters were all under the impression that there was something peculiar or mysterious about the whole business. Had Blevins and Woodruff once been partners? Had a fortune in rubies been destroyed out of ignorance? Had it been destroyed at all? Did Blevins get it? Did Woodruff? At this point we need a script writer. In any case, there is agreement that the proceeds of the sale of the stacked “Tanganyika Artstone” had financed the first real mining operations at Longido, decades after the original find. Each owner of the Longido property has in his turn reluctantly concluded that, with the exception of unspectacular “gem pockets” which are discovered once a decade, or even less frequently, the Longido rubies cannot be profitably removed from their host rock. Too much labor and too much breakage are involved. In time, the Longido has ceased to be a gemstone mine, though it continues to produce the decorative red-and-green artstone prized for making ashtrays and carvings.

gemstone

Both the bright red of the ruby and the bright green color of the encasing grains of the mineral zoisite are produced by trace amounts of the element chromium in the host rock. Anyolite (from anyoli, Masai for “green”) is the proper geological name for the Tanganyika Artstone but in Tanzania even the Masai say “ruby-in-zoisite”.

Although “ruby-in-zoisite” is in no way incorrect, the name became a source of confusion in the late 1960s when tanzanite (which is a variety of zoisite colored by traces of vanadium, not chromium) was discovered, for people in Tanzania and Kenya had come to believe that “zoisite” had to be green.

John Saul

Secret Valleys

Geological explanations – Secret Valleys

Secret ValleysEven geologists rarely appreciate the great age of East Africa’s Rift Valley System. Rifts are formed and are later completely filled-in by erosion as their shoulders collapse and wash down into the valley below. Eventually the rifts are eroded beyond easy recognition, and new rifts open, whether in the same place or elsewhere in the region, to accommodate renewed stresses in the Earth’s crust as tectonic plates shift.

It appears that rifting had occurred in what is now East Africa as far back as 550 million years ago, permitting rock, fluids, and heat to flow upwards in a unique geological episode known as the Pan-African Event. This one-of-a-kind “heat pulse” is associated with the formation of deposits of colored gemstones right across the southern continents and even in far-away Brazil where it is also called the “Pan-African Event”.

One rift of Pan-African age, hundreds of kilometers long, has been so severely eroded that it is now entirely flat. That means you can walk right “off” the shoulder of the rift, across it, and on to the other side without ever encountering hills or bumps any higher than the local termite mounds. Only the type of rock changes, from 1a) thin-bedded rocks a bit like a layer cake, to 2) massive, monotonous, valley-fill rocks, and back to 1b) thin-bedded rocks on the other side of what had been a Rift Valley in times long before the dinosaurs.

Ancient geological faults which cut these secret or disguised valleys turn out to be good places to prospect for deposits of gemstones, but no one knows quite why. One guess is that these ancient faults, which are also eroded and difficult to detect, had intersected the Earth’s “deep plumbing system”, thereby permitting rocks, fluids and heat to rise from unusually great depths.

John Saul

Our grandfather knew members of the Arpels family who wound up with some fine stones.

The John Saul Ruby Mine (JSRM)

The first gemstone deposit to be found in East Africa was the ruby deposit at Longido, Tanzania. Other ruby deposits were discovered in Tanzania subsequently, most of them of the anyolite type, as at Longido, but production was generally small or of poor quality gems or of rubies which had been fractured in attempting to free them from their host rock. Then in mid-1973, our father received a visit from a Park Ranger from Tsavo West National Park. The ranger, Frances Wainaina, had some nicely crystallized fragments of tourmaline, a gemstone which comes in almost any color.

Although the fragments were not quite gem-quality, they had clearly come from large crystals – larger than a finger, it would turn out – and were well crystallized in places. But most importantly, they were of the splendid tone of green readily associated with the presence of chromium. Further, they were accompanied by other minerals which were also nicely crystallized, a good sign when prospecting for colored gemstones. (The term “colored gemstones” is a trade term for transparent or translucent gems other than diamonds. By convention, yellow and blue diamonds are not “colored gemstones”, but colorless tourmalines or sapphires are…)

Dad, a geologist, was familiar with the area and liked what he saw. Although he had confidence in the Park Ranger, he took the preliminary step of sending a small field team led by his long-term employee Mwaura Bagite to bring back additional samples. For when tracking the origin of someone else’s mineral samples, gem or not, it is wise to verify if they actually came from where they are said to have been found. (Years before, Dad had been shown a sample of small fractured rubies said to have come from “a deposit very near Nairobi”. After much running about, he discovered that they had come from the pathway to the Sapieha chapel!)

In this case, the chrome-green tourmalines did indeed come from where the ranger had said, and there were many more of them, but only a few which were at all transparent. But their color was promising.

Following the several months it took to obtain the permits to prospect in a protected area, Mwaura was again sent to the site and when he dug the first test pit as instructed he found himself in what geologists sometimes call “rotten rock”. In fact, he was digging at the very edge of a block, some 500 m wide by 100 m long, of a so-called “ultrabasic intrusive”, a chromium-rich rock that had been brought up from a depth of some 30 kms in a process not unlike the squeezing of toothpaste from a tube. The chrome-tourmalines had formed at the very edge of the encasing rocks and were of little value. But in the contact zone with the intrusive were large good quality rubies brought up from deep in the Earth, also colored by chromium.

The JSRM was called the “Nganga Location” in the Mines Departments register. The deposit produced gem green tourmaline before the first ruby came out, the green of the tourmaline and the red of the ruby both coming from the presence of trace quantities of chromium. Kenya mining regulations were not the same for these two materials, with ruby classified as “precious” and tourmaline as “non-precious”.

The very first person to spot a speck of a red mineral was another employee, Henry “Cowboy” Asusa, a Kenyan who wore a Stetson and had an improbable way about him. Cowboy possessed a John Wayne demeanor, spoke in slow American-accented English, and had a potbelly and asqueaky voice. He was a city person who hated the bush and would use anything as a pretext to return to Nairobi (which is probably why he had lost previous jobs as a tour guide). In any case, Cowboy came rushing into Dad’s office after just a couple of days in Mwaura’s camp crying “Ruby! I saw a ruby!”.

Dad chartered a small plane whose pilot reluctantly landed at a Parks Department airstrip close to Mwaura’s camp, insisting once he got on the ground, that nobody look at any of rocks until the warthog holes on the strip had been filled-in. Nobody did his bidding (though he was given a shovel) and in consequence he and other pilots refused to land on the strip on flights in the days which followed. The Voi Airstrip, 50 miles away, was used instead. This strip, which was at the time warthog-free, is well known to those who have seen “Out of Africa” for it is there that Karen Blixen’s great love, Denys Finch Hatton, crashed and died in May 1931.

Everyone had been right, the Park Ranger, Dad, Mwaura and Cowboy, and The Ruby Rush was on! Mining at the outset was very easy. For the intrusive, which had certainly been very hard when it formed thirty kilometers (almost 20 miles) down, was chemically unstable in the wet, oxygen-rich, low-pressure, low-temperature conditions at the Earth’s surface. It wasn’t just a bit “rotten”, it was falling apart. In a section of the deposit which would be nostalgically referred to as “the crumbly zone”, rubies had been extracted with the bare hands, not from soil, but from their primary host rock.

These mining locations were extensions to the main block of claims at the JSRM. Mungai was an excellent employee who did much of the actual pegging at various sites. People would follow Dad in the bush and peg next to him and some got wealthy by doing so. First production from the JSRM, but not all of the 120 kilos were gem quality! Gordon Tait, who signed the export authorization, was a highly knowledgeable civil servant who often came to work in a kilt, much to the approval of the Maasai whose own apparel, known world wide, had been inspired by the Scotch kilt.

The color of these stones was splendid and their discovery put East Africa on the map of gem-producing countries along with the classical gem-producing lands of Burma and Ceylon (Sri Lanka). Indeed some of the rubies from the “John Saul Ruby Mine”, as it came to be called, were of the fine distinctive shade of ruby-red which would become a standard of quality. On a trip to the gem-cutting center of Jaipur in Rajasthan in the 1980s, Dad was offered a ruby by an Indian cutter who insisted in broken English that it was “johnsaul”. Dad’s Indian translator tried his best to explain who Dad was but he had no luck. To the cutter, “johnsaul” was simply the English word that meant “very fine red”.

Our grandfather knew members of the Arpels family who wound up with some fine stones. This is overstated. A good 99+ percent of the stones mined were either bead quality or simply waste.

All good things come to an end and within a short period of time, extracting rubies from The John Saul Mine became hard work, as is the case for virtually all gemstone mining worldwide. That is one of the reasons why gemstones are expensive.

The JSRM in later years. The plant, technically known as a “sink-float” plant, was called “the chunga-chunga” in both English and Swahili. The picture with the truck was taken of the “Kimbo Pit”, named after our dog (who himself was named after a local brand of margarine). The Kimbo pit produced very large quantities of low grade stones.