Impressive tsavorites

Tsavorites have been discovered in vary few places around the world. They are mainly mined in Tanzania (the Lemshuko tsavorite mine) and Kenya. Tsavorites are also found in Madagascar but in smaller sizes and quantities. Tsavorite is not only rare but even more so in bigger sizes. It is generally estimated that only 1% of all tsavorites are above 3 cts (after cutting). Tsavorites are formed under specific conditions; the important heat and pressure which formed tsavorite shattered most of the stones. Tsavorites, if not shattered, are expected to be included. A clean 3 cts tsavorite of the right color is thus not easy to come accross.

Swala Gem Traders has bought and mined a few very large pieces (some of which are pictured below). If a 3 cts tsavorite is considered large, how about a 20 cts gem? and a 50 cts? how about a 100 cts + tsavorite?

These huge pieces don’t seem to make much sense, do they? It seems as if they would have to defy nature to be so big and clean.

Pictures in this article are of from the Swala collection.

130 cts tanzanite

130 cts tanzanite

This 130 cts tanzanite was cut last year. Everything about this gem is nice: color, size, clarity, cut. This tanzanite is obviously too heavy to be worn. It’s either a museum piece or a collector’s item, not really an everyday ring.

Large tanzanites are not frequent but they do exist. Rough zoisite is generally quite clean, certainly much cleaner than other East African gems such as tsavorites or spinels. If not blasted to pieces during the mining process, large zoisites do come out.

This 130 carat tanzanite was cut last year. Not surprisingly, the color is very nice. Tanzanite usually needs depth in order to be saturated. It could have turned out too dark, but didn’t.

130 cts tanzanite

Photo credit to Patrick Voillot expedition.


Winza corundum (ruby and sapphire)

Just a few pictures of the Winza corundum (ruby and sapphire). Swala Gem Traders had financed a team of ruby and sapphire miners in Winza. Multiple kilos of Winza corundum were brought back to us. Obviously, much of rubies and sapphires were either useless or of cabochon quality. Plenty smaller pieces (0.3-0.4cts) were beautiful and facetable. A few larger and very attractive pieces (above 3 cts) were also cut.

Winza Corundum


The Winza corundum (ruby, sapphire) displays interesting difference in colors, saturations and tones. Like most deposits, plenty of rough needs to be examined before finding nicely crystallized gems.

Bi-color Winza sapphire Bi-color Winza sapphire

Multicolored Winza sapphires can be found, rather unusual and collectors’ material.

Pink and red Winza corundum are found. Some of which of exceptionnal size/clarity/color combination.

More technical articles on Winza rubies can be found at the following links:

– Vincent Pardieu and Jean-Baptiste Senoble’s 2009 expedition to the corundum deposit in Winza


Vincent, with Mark at Swala Gem Traders’ office during Vincent and Jean-Baptiste’s trip to Winza.

– An expedition to Tanzania’s new Ruby deposit in Winza – InColor (pages 44 and onwards)

– Rubies and Sapphires from Winza, Central Tanzania – Gems & Gemology

Majestic Tarangire (northern Tanzania) elephants no gems could buy.

red spinel

Like a phoenix, red spinels on the rise

“Spinel: resurrection of a classic” is a nice overview of red spinels (including the Mahenge spinels of course) around the world. Article by Vincent Pardieu, with Richard Hughes

red spinels

In decades and centuries past, two strikingly different reasons have prevented gem spinels from reaching the general public. Many possessed a nasty secondary gray tint to them or, in the case of red spinels, they might be so strikingly spectacular that they passed as exceedingly fine and valuable rubies. Many of the nicest and greatest “rubies” found in royal crowns are in fact red spinels. Thus it is that the “Black Prince’s ruby” and the “Timur ruby”, both of which are in the possession of the British royal family, have turned out to be spinels. In recent years Tanzania has produced some splendid red and pink spinels, a gemstone which is decidedly undervalued. Although known since Roman times, spinel is not one of the traditional birthstones and its name is so unfamiliar that our spellcheck program questions whether we had not meant to type “spine” or “spineless”.

red spinels


We are happy to be able to say that these days Tanzania produces lovely gem spinels with no hint of gray and at prices that do not demand a Royal budget (more so for smaller spinels). Tanzania is now becoming very famous for its spinels. Spinels from southern Tanzania (Tunduru) are of various colors (purple, blue, etc) while those from central Tanzania (Mahenge, Morogoro) are usually pink to red. The latter are the most expensive. In 2007, a couple of incredible rough pieces have been mined. Quite a few articles have been written about this rough. We have been purchasing Mahenge spinels for years. We buy these spinels on a day to day basis. We were also among the privileged who bought these huge gems. The smaller spinels are usually pink whereas the bigger ones (above 7 or 8 cts) tend to be red. Our smaller spinels are sold to cutting factories in the far East. Our bigger ones are usually sold to private collectors, to well known retailers and wholesalers.

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.

Fancy zoisites

The beauty of fancy zoisites

Tanzanites, as we all know, are blue. They are blue crystallized zoisites. Tanzanites are almost always (>99.9%) heated in order to obtain their famous blue/purple-blue color. Heating is quite straight forward (compared to other gemstones…): approximately 600 degrees Celcius for 15 minutes. Once heated a tanzanite will more or less have a uniform color whatever the axis. Tanzanites/zoisites are trichroic gems which implies that the color should be different – whether easily perceptible or not – according to the axis. Heating tends to “blend” all colors into the blue one.

A cutter will try as often as possible to put the tanzanite’s “table” on the blue axis. Chosing the axis for the table will play a role on the gem’s final color.

A rough zoisite however (hence not heated) will often easily display its trichroism. Usually rough zoisites will show unattractive colors such as brown or yellowish brown. Because of their relative unattractiveness these zoisites will be heated into nicer blue tanzanites. Once in a while, a piece of rough zoisite will show an attractive non-blue color. In such rare instances, it is wiser not to heat the gem… These colors will more often be green or yellow but with luck, rough zoisites caLet’s discover n also be orange or pink.

Over the years we’ve collected zoisites which were “naturally” attractive. Instead of heating them, we’ve decided to cut them and keep preserve their natural colors. Pictures below show zoisites of very different colors, of almost of colors in fact.


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.


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.


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