Our Tsavorite Mine - "Lemshuko Mine" at Komolo, near Arusha, Tanzania.
Tsavorite: history of the main deposit
Splendid brilliant green grossular garnets were first discovered in Tanzania in 1967 near the small village of Komolo some two hours south of Arusha, "capital of Maasailand". A few years later, similar stones in smaller sizes were found just outside Kenya's Tsavo West National Park and in 1974 Tiffany & Co. introduced this new gemstone to the world market under the name "tsavorite".
At the Komolo tsavorite deposit, which is also known as the "Lemshuko Mine", tsavorite occurs in two distinct geological settings, a primary or "hard rock" deposit, and as redeposited in secondary alluvial sands and gravels. In the decades since the tsavorite's discovery, local miners have blasted the hard rock and dug pits in the sand and gravel deposits, and have even attempted some tunneling in places where the garnet-rich gravel was sufficiently consolidated. Yet, because of the difficult access to the Komolo area and shortage of capital, no one had attempted the mechanized mining of tsavorite.
After purchasing consistently nice rough tsavorite from miners over a period of several years, Swala Gem Traders decided to get involved in mechanized mining at Komolo.
We began working the alluvial deposit, with particular attention to areas covered by soft sand that had made the terrain too dangerous or expensive to dig by hand. In many of these places mining tsavorite was relatively easy and the workers operating excavators and back-hoes were entirely safe.
Our approach is straightforward. Once we locate a promising zone in the alluvium, we use a Caterpillar or a back-hoe to fill our trucks. The trucks empty their loads in a nearby trommel which separates material by size and we process the usable sizes in a water jig which then separates the sized gravel by specific gravity. Tsavorite is heavy, with a density 3 1/2 to more than 4 times that of water, so at the end of a good run, the output of the jig will shine with the magic of green tsavorite garnet!
This is theoretically simple and is indeed so in a laboratory, but in the middle of the bush, dust, lack of sufficient water, and wear and tear on our machines are constant concerns, not to mention the disconcerting roar of the occasional lion...
Our output includes gem tsavorites in sizes ranging from very small (under 0.1 grams) which we send to lapidaries in Bangkok, Rajasthan and the Bombay area, to large and spectacular individual stones. These tsavorites we cut ourselves and sell to private individuals or to jewelers in places such as Place Vendôme in Paris, where they eventually become the center stones for fine jewelry.
Tsavorite: characteristics
Tsavorite has an established reputation as a valuable gemstone whose production is essentially limited to East Africa. Tsavorite has magnificent sparkle with a superbly vivid green color which attracts the eye of novice and expert alike. Its color is entirely natural for in common with the other members of the garnet family of gemstones, the color of tsavorite cannot be enhanced by any treatment. Tsavorites are very tough and can be worn for decades without showing the slightest sign of wear. In this respect and by its color too, tsavorite is a rival for emerald, a far more fragile gem.
Tiny tsavorites are not rare, but stones sufficiently large to be the center stone in a ring are not easy to come by. We believe that this is because the incorporation of traces chromium and vanadium, which act as coloring-agents, affects the crystal lattice in ways that make it difficult for individual crystals to grow past a certain size. In consequence, large tsavorites are much rarer than large emeralds.
Interestingly, occasional pockets of tsavorite are also found in the Tanzanite mines at Merelani. These gems are commonly much larger than the tsavorites from Kenya. They are also slightly paler with hues in shades of mint green. These "Mererani Mints" tsavorites are very lively, with colors rarely seen in the gem world due to their incorporation of an unusual mix of traces of chromium, vanadium and iron.
Tsavorites at Swala Gem Traders
Over the years we have had access to the finest tsavorites and have handled some of the world's largest and finest, including a few cut stones over 50 and 100 carats. When an exceptional tsavorite is mined, it is likely to end up in our office.
Sizable tsavorites are extremely rare, especially when the gem is clean and the color ideal. We sell exceptional stones when available and always maintain substantial stocks in the sizes and qualities more commonly demanded. We cover all sizes.
|
Our participation in associations and our exchanges with the specialized press, geologists, gemologist or gemstones lovers, led us to receive regularly groups of visitors at the tsavorite mine. It is always a pleasure.
Association Française de Gemmologie (A.F.G.) at the Lemshuko tsavorite mine |
Location Overview
|
The manager's house stands on a hill in the middle of a valley surrounded by mountains on three sides. The fourth side opens on the vast plains of the fabulous East African tablelands, "the Maasai Steppe" - Picture taken at the Lemshuko tsavorite mine
The plain on the left reaches an altitude of close to 1000 meters - Picture taken at the Lemshuko tsavorite mine
The road from Arusha passes through a small village full of independent miners who do not hesitate to dig galleries hundreds of meters long in order to poach tsavorite from Swala Gem Traders property. As can be seen in some of the next pictures, this can become a security problem for machines and men - Picture taken at the Lemshuko tsavorite mine
|
The tsavorite Mining Process
Step 1: Reaching the gravels rich in Tsavorite Garnets.The first step is to identify areas where the secondary deposits are, and remove the sterile overburden down to the gem-bearing sands or gravels. Our machines occasionally encounter obstacles such as big rocks or galleries that can be harmful for men and machines - Picture taken at the Lemshuko tsavorite mine
The galleries can be 2 meters high and are not secured or supported by mine timbers. They are dangerous for everybody concerned, including the independent and illegal miners who dig them. The risk is greatest during the rainy season - Picture taken at the Lemshuko tsavorite mine
The ground collapsed under the weight of our Caterpillar. The men have to fill in the hole with rocks, and another machine will come to rescue of this one - Picture taken at the Lemshuko tsavorite mine
|
Step 2: Get rid of the dust.The gravels are trucked to this small station where the dust and the large sterile rocks are removed. In the picture, the dust is going to the right and the oversized gravels to the left. Mark is supervising.
This rotating machine is made of 2 cylindrical sieves.
|
Step 3: The Jig.The trucks bring loads of gravel by this point almost free of dust - to the top of the jig. Water will be used to wash these loads before going through the final sorting process. Under the rotating sieves is a pile of large-size gravels in which we occasionally find a nice sized Tsavorites - Picture taken at the Lemshuko tsavorite mine
Gravels being washed. They will then be released into the flowing water and carried down the chain. This powerful water jet will remain in use until all the gravel has been sorted. Water is scarce at Komolo and is recycled in closed circuit. Evaporation is a problem - Picture taken at the Lemshuko tsavorite mine
Mark is here following up the sorting in the right-hand part of this double jig. This double-jig set-up allows us to continue washing on one half while hand-sorting on the other. The compartments are designed to slow down the water which carries the washed but unsorted gravel. A powerful pump is pushing water up from beneath in order to keep the gravel in motion and avoid clogging the system.
Here Mark is opening the second part of the jig at the end of a day's run. Gravels cover the entire rack of each compartment. This system imitates Nature when rivers carry stones, diamonds or gold. The compartments simulating natural "placers" or cavities created by large rocks in river beds - Picture taken at the Lemshuko tsavorite mine
Mark supervising the compartment sorting and possibly noticing something green and shinning - Picture taken at the Lemshuko tsavorite mine
When the work is going well, the mine runs day and night. This picture was taken in the evening when the workers finally stopped the pump to clean the jig - Picture taken at the Lemshuko tsavorite mine
|
The water is the key element for the mining activity.These two reservoirs work like a small water purification system. The sand and the mud are carried by the water to a first reservoir, a "settling pond". Clean water remains on the surface and is pumped from the first reservoir (right) to the second one (left) - Picture taken at the Lemshuko tsavorite mine
The jig is pumping and sending muddy water directly into the reservoir. A circular aqueduct runs along the side of the first reservoir. We use it to carry waste water directly to the second reservoir when the first one needs to be cleaned - Picture taken at the Lemshuko tsavorite mine
Hereunder, the first reservoir (left) is full of clean water pumped from the reservoir 2 on the right hand side. The washing and sorting station will now work with the reservoir 1, so the men are connecting the pipes and the pump together - Picture taken at the Lemshuko tsavorite mine
When the pipes are connected, the pump can be started again - Picture taken at the Lemshuko tsavorite mine Photographs and comments by Yannick Mandaba. |
