The history of Antsongombato gemstone mine

Rhodizite

In 1834 was described a rare mineral – rhodizite. In spite of its long history (most of the other minerals were discovered later), rhodizite turned out to be a true rarity. Crystals of visible size are found just in three countries – Madagascar, Russia, and the USA (Wisconsin).

Specialists since the 1920ies noticed that the largest and most interesting rhodizite crystals are in Madagascar. The first crystals of a gem-quality rhodizite were found in the central part of Madagascar in the 1920ies in Sahatany Valley some 35 km from Antsongombato.

Discovery of a new mineral near Antsongombato

The pegmatites at Antsongombato, on the northern slopes of Mount Manentoakoho were known already since the early 20th century due to beautiful red tourmalines from these rocks. In the 1930ies, though, this area was abandoned and mines became less known.

The interest of gem prospectors in the pegmatites of Antsongombato renewed in the 1960ies when some gem-quality rhodizite crystals (or – maybe londonite?) were found there. Some of them were faceted, but one especially beautiful sample of 7 cm large rhodizite-londonite crystal was brought to the Museum of the School of Mines in Paris.

Only around 1995-1998 experienced mineralogists started to research the unique local minerals more closely. In October 1998 a new set of pegmatite dikes was discovered and the gorgeous yellow crystals were just too intimidating. It turned out that these crystals have a different chemical composition – cesium-aluminum-beryllium borate while rhodizite is potassium-aluminum-beryllium borate.

This new mineral was named londonite to mark the exceptional input of mineralogist David London (b. 1953, University of Oklahoma) in the research of the formation of granitic pegmatites.

Londonite was approved as a new mineral in 1999 and named in 2001 (2.).

History of mining

Already in late 1998 Madagascan company “Pyramide” started mining there. Mining was done carefully, by hand in order to preserve as many crystals as possible. Besides the gemstones, they mined also beautiful collector’s material: yellow londonites-rhodizites together with red tourmalines and blue apatites. Active mining continued until January 2001. Since then mining activities have decreased although, most likely, there still are fine londonite and rhodizite crystals.

In total, some hundreds of grams of gem-quality londonites and londonites-rhodizites were mined and more than 300 carats of gemstones were faceted from these crystals. The largest faceted gems rarely exceed the weight of 2 carats.

Pegmatites with the unique yellow stones

Londonite crystals have been found just in three locations: a) near Antandrokomby in the Manandona Valley (Antsirabe Region); b) near Ampanivana (Betafo Region); and c) near the abandoned village of Antsongombato (Betafo Region) – the only find of gem-quality londonite crystals in the world.

These pegmatites formed in the crystalline rocks of the Proterozoic Itremo Group. Usually, pegmatites are belts – layers of large crystals in otherwise usual small-crystalline rock and this is the case in Antsongombato as well. There the pegmatite belts can be more than 500 m long and, mostly some 30-40 cm wide, in some places becoming up to 6 m wide. All gem-quality londonite comes from just one of these pegmatite dikes.

These pegmatites are rich in other fine minerals, such as red tourmalines, beryls, béhierites, and schiavinatoites – the last one also is found only in Antsongombato!

It is very hard to distinguish londonite and rhodizite. Sometimes even one crystal can have patches of rhodizite and londonite in it.

Crystals of these minerals are up to 8 cm large and may have no color at all or be white, yellow, and deep brownish-yellow. Londonite is hard – 8 on the Mohs scale, and it has no cleavage. Both are great qualities for gems.

But – there is also a drawback: the yellow color of londonite fades if the jewel is under direct sunlight. The saturation of the yellow color can be improved by irradiation, but this coloration will fade in sunlight even faster.

References

1. Brendan M. Laurs, Federico Pezzotta, William B. (Skip) Simmons, Alexander U. Falster, and Sam Muhlmeister, Rhodizite-Londonite from The Antsongombato Pegmatite, Central Madagascar. Gems & Gemology, Winter 2002. Page accessed on the 29th of December 2022.
2. Simmons, W.B., Pezzotta, F., Falster, A.U., Webber, K.L., Londonite, a new mineral species: The Cs-dominant analogue of rhodizite from the Antandrokomby granitic pegmatite, Madagascar. Canadian Mineralogist: 39: 747-755. Page accessed on the 1st of January 2023.

Antsongombato Gemstone Mine is included in the following article:

Diaspore

Diaspore is a fairly common mineral – aluminium oxide hydroxide. Together with chemically similar minerals – gibbsite and boehmite – it forms bauxite rock, the main ore of aluminium.

Diaspore can form rather large crystals that, for the most part, are opaque or translucent, in transparent or brownish-grey color. The hardness of diaspore is comparable to the hardness of quartz: 6.5 to 7. Thus, if it would be transparent and with a bright, clear color, it would be a fine gemstone.

And there is such diaspore!

The only csarite mine in the world

The bauxite mine in Ilbir Dağ – Ilbir Mountains – in the southwestern part of Turkey has been known for many decades.

This İlbirdağı diasporite deposit consists of primary, metamorphic bauxite, and secondary bauxite that has been re-deposited by hydrothermal processes and consists mainly of diaspore. Such secondary bauxite is rare.

In this secondary bauxite formed fracture zones, and the mineral was once more redeposited in these fractures during the Late Paleocene, Eocene, and Oligocene. Thus formed unusually large crystals of diaspore.

The gem qualities of these crystals were noticed in the 1970ies or earlier, but, this gem has one serious drawback: a cleavage. Crystals of diaspore easily break along one plane. Cutting jewels from this mineral requires excellent skills and many attempts for testing and trying.

Nevertheless, in the mid 1990ies a private entrepreneur started the mining of gemstones in the abandoned bauxite mine. The first cut stones appeared on the market in 1997.

The first large gemstone was 80 carats large and made in 2008. In 2009 was cut 96 carats large stone named “Sultans Shield”. The value of this gem then exceeded 1 million dollars.

Thus far other finds of these gemstones are not reported and the csarite mine in Ilbir Dağ seems to be a unique natural wonder.

The exact location of the only gem-quality mine of diaspore is not widely published and Wondermondo respects this approach. The map shows one of the nearby villages.

Color change and extreme price

These stones got much attention due to their unique quality: the color change effect.

In bright daylight, they are light green to brownish, but in less intense incandescent light, they are carmine red. Some stones may have even three colors – light green, golden and carmine red.

Just a few gemstones have such pronounced color change effects: alexandrite, kyanite (pleochroism effect), and some others.

Another amazing quality of csarite is its natural beauty. The vast majority of gemstones in the market are improved in one or another way: heated, colored, coated, etc. Csarite does not need any such activities.

But owners of csarite should be careful: the stone breaks rather easily along the cleavage plane.

This gemstone is very, very rare. Most of the diaspore crystals in the world’s only mine are not suitable to be gemstones – they have dull color, fractures, and inclusions.

Most of the mined stones are lost as well – they break along the cleavage plane during the mining or cutting. Just a few percent of all the crystals turn into gemstones.

Due to its extreme rarity and unusual beauty, this stone may cost from 500 to more than 10 000 USD per carat. Thus csarite is one of the most expensive gemstones in the world.

Trade names: zultanite® and csarite

In 2005 A. Murat Akgün obtained the rights for gemstone mining in Ilbir Mountains.

The unique gemstone initially was named “a color-changing gemstone from Turkey” or other complex names. The name of the mineral – diaspore – was not much used and the new owner did not like it (“sounds like a fungus”).

The first trade name was zultanite® after the Sultans of the Ottoman Empire, with a ‘z’ to distinguish it from another mineral called “sultanate”.

Some years later a legal battle between the partners led to the temporary loss of the right to use this trade name by the owner of mine “Milenyum Mining Bauxite Establishment”. In response to this situation was introduced another name – csarite.

Now, as the legal battles are settled, both names are in use. Zultanite® and csarite are the same gemstones from the same mine, the only csarite mine in the world.

References

1. Stephen Kotlowski, A Short History of Diaspore and its trade names Zultanite and Csarite. The International Gem Society (IGS). Page accessed on the 1st of December 2022.
2. Murat Hatipoğlu, Cahit Helvacı, Steven C. Chamberlain Hakkı Babalık, Mineralogical characteristics of unusual “Anatolian” diaspore (zultanite) crystals from the İlbirdağı diasporite deposit, Turkey, Journal of African Earth Sciences
   Volume 57, Issue 5, July 2010, Pages 525-541. Page accessed on the 1st of December 2022.

Csarite mine in Ilbir Mountains is included in the following article:

Varieties of quartz

Quartz crystals come in several amazing varieties: colorless and pure (rock crystal), rose-colored (rose quartz), grey (smoky quartz), black (motion quartz), and many others.

One of the best-known varieties is amethyst, a stone with an otherwise rare color for transparent gemstones: purple. Most frequently this color is created by ferric particles in the crystal. Amethyst is found in many locations around the world and belongs among the most popular gemstones.

Another well known variety of quartz is the yellow citrine. Gem-quality citrines are a lot more seldom in nature and most of the citrine in the market is created artificially, by heating and irradiating less valuable pieces of amethyst. The coloration mechanism of citrine is not entirely clear, but, formally, iron-colored quartz is not considered to be a citrine even if it might have a brownish-yellow color.

And then there is amethyst-citrine or ametrine – gem quality stone which is part amethyst and part citrine (although, formally this yellow quartz is not a citrine because it is colored by iron). Occasional finds of these stones are known in several places around the world (Mozambique, Canada, and the United States) but there is only one commercial mine of this unusual gemstone: Anahi Mine in Bolivia.

Geography and geology

Anahi Mine is located in the very east of Bolivia, near the border with Brazil. It is located on the western slopes of a low ridge that rises some 200 m above the surrounding plains of Pantanal.

This part of Bolivia still is fairly virgin. There are no roads, no fields, and no clearings in the forest, except for the mine and airfield near it.

This ridge is a fault line, where limestone and dolostone rocks have contact with quartz. Over the millions of years, the limestone and dolostone in many locations of this contact zone have been dissolved by water. But during this extremely long process crystals of ametrine formed in the quartz layer. The several meters large cavities in these contact zones are completely covered with these crystals.

Legend of princess Anahí

According to a legend, in the 17th century, a Spanish conquistador, Felipe de Urriola y Goitia, married a princess of the Ayoreo people. The name of the princess was Anahí and as a dowry, the Spanish conquistador received a cavern that was lined with these unusual jewels. A sample of this stone – the necklace of princess Anahí – reportedly was presented to the Spanish monarch.

This legend in slightly different forms today is repeated and is fairly popular, but, unfortunately, there are no facts to prove it.

The fate of Ayoreo people today is not simple. Part of these people live in the rainforest and prefer to be uncontacted tribes, part is trying to adjust to contemporary life in Bolivia and Paraguay.

The history of Anahi Mine

Illegal mining

During the following centuries ametrine stones appeared in the markets of this part of South America but the location of the mine was not known to the general public. It is possible that Ayoreo people occasionally mined these stones and sold them in the nearby markets.

In the late 1970ies started more intense mining activities. By this time jewelers realized that two-colored quartz is not an imperfection but rather a valuable peculiarity. Miners arrived from Brazil, Paraguay, and, of course, Bolivia and were illegally digging the stones, although the area was guarded by a military station that was located nearby. According to local stories, this was made possible by bribes.

The access to the mine and reaching the nearest markets and selling the gemstones was an adventurous and risky feat. Bolivia did not allow mining ametrine and Brazil did not allow importing these stones from Bolivia. Nevertheless, they reached Brazil and, to hide the violations, sold as stones that were mined in Brazil. To hide the traces of these deals, miners facilitated rumors about the finds of ametrine in diverse locations in Brazil and even in Uruguay.

Due to these conflicting messages and no traces of real mining in Brazil, many gemmologists considered that ametrine is not natural.

Some specialists in the 1980ies even managed to create it artificially by irradiation and heat treatment of a natural Brazilian amethyst – although the result was not too similar to real ametrine. More successful was the synthesis of ametrine in Russia in the 1990ies – this material is hard to distinguish from natural ametrine.

Contemporary mining operations

In 1990 Anahi Mine was obtained by its present owner – a Bolivian company Minerales y Metales del Oriente. The new owners named it in the name of the legendary princess Anahí.

The location of the mine became publicly known and the sales of raw materials were allowed as well.

The access to Anahi Mine is not simple even today. Around the mine are virgin rainforests and swamps. Some kilometers from it is a dirt strip for single-engine aircraft that operates only in the dry period of the year.

Mining is done in pits and trenches – today all the mining is underground.

The most abundant gemstone of Anahi Mine is a high-quality amethyst. This stone should be protected from bright light to avoid the loss of its color. There is mined also a lavender-colored variety of amethyst. This unique stone is called anahite. Anahi Mine is also one of the rare large-scale sources of high-quality yellow quartz that is called citrine, although, as mentioned above, formally this is not a citrine.

But, of course, the best-known jewels in Anahi Mine are ametrines.

References

1. Paulo M. Vasconcelos, Hans-Rudolf Wenk, and George R. Rossman, The Anahi Ametrine Mine, Bolivia. Gems&Gemology, Spring 1994. Page accessed on the 29th of October 2022.
2. Minerales y Metales del Oriente, the official website of the owners of the mine. Page accessed on the 30th of October 2022.

Anahí Ametrine Mine is included in the following article:

Description of grandidierite

French mineralogist Alfred Lacroix discovered grandidierite in 1902 in the seaside cliffs of Cap Andrahomana, southern Madagascar. Later, in 1960, no more grandidierite was found on this site.

He named the mineral after a French explorer Alfred Grandidier (1836-1921).

Grandidierite is a bluish-green stone that is well suited to be a gemstone:

• It has a rare, interesting color. Most of the blue-colored gemstones are artificially “improved” by heating or chemicals, but grandidierite has a naturally intense color.
• The stone is hard: 7.5 by Mohs scale – harder than quartz and a lot harder than, for example, glass.
• It has a strong pleochroism: when turning a transparent stone, it changes the color from colorless or pale yellow to blue-green, and then to neon blue. This is an interesting feature but it makes the life of a jeweler a lot harder: craftsmen should plan well the faceting of the stone to show the beautiful blue-green color.
• One characteristic, though, makes it harder to process: the stone has a well-expressed cleavage, e.g. it divides along specific planes irrespective of the wishes of the jeweler. Due to this: if you are one of the few persons on the planet who can touch a grandidierite jewel, be careful and do not drop the stone, it may break up. That would be a huge loss!

Even opaque pieces of grandidierite that are not gemstones, are very rare. The stone is found in small quantities in Algeria, Antarctica, Canada, New Zealand, the USA (New York, Wyoming), India, and some more countries.

It is estimated that one out of 10,000 pieces of grandidierite is a true gem.

Tranomaro grandidierite

In May 2014 there was discovered a find of transparent, gem-quality crystals of grandidierite near Tranomaro. Stones were found in a weathered pegmatite with two grandidierite veins. Before this, just a few totally transparent pieces of grandidierite were found in Sri Lanka and also in southern Madagascar, Cap Andrahomana.

Tranomaro grandidierite is mined with simple methods: up to 15 m deep pits. The area is not safe for travelers: there are reported attacks by gangs. The mine is not accessible by car.

Until March 2016 there were mined some 800 kg of grandidierite. This is an unusually large quantity! But only 60 g or 300 carats (!) of this mass were transparent gems!

Nevertheless, nice crystals of translucent grandidierite there were up to 15 cm long and 930 g in weight.

Too rare for the market?

The largest known grandidierite gemstone is 78 carats large, owned by Joseph Fam, Singapore. This is a faceted stone, but it is not entirely transparent but rather translucent.

In Wilensky Gallery (New York, USA) in 2019 were presented three wonderful crystals from Tranomaro, respectively 2.86, 3.14, and 4.96 carats large. Their price was, respectively, 69, 78, and 129.5 thousand USD. These are not the most expensive gemstones in the world but are not very far from the most expensive ones. In fact, before the discovery of the Tranomaro grandidierite, the very first known piece of transparent grandidierite was sold for 50 thousand USD in 2003, although it weighs only 0.29 carats. This stone was found in Sri Lanka.

In general, it is assumed that there simply is no market and no set price for these stones because they are too rare and deals are too few.

Mineralogically similar to grandidierite, but even rarer is another gemstone: ominelite. There is only one find of gem quality stones of this kind: Misen River ominelite find in Japan.

References

1. Delphine Bruyère, Claude Delor, Julien Raoul, Rufin Rakotondranaivo, Guillaume Wille, Nicolas Maubec, and Abdeltif Lahfid, A New Deposit of Gem-Quality Grandidierite in Madagascar. Gems&Gemology, Fall 2016, Vol. 52, No. 3, page accessed on the 24th of July 2022.
2. Wim Vertriest, Stanislas Detroyat, Supharart Sangsawong, Victoria Raynaud, and Vincent Pardieu, Grandidierite from Madagascar. Gems&Gemology, Winter 2015, Vol. 51, No. 4, page accessed on the 24th of July 2022.
3. Brecken Branstrator, 5 Things to Know About … Grandidierite. National Jeweler, April 008, 2019. Page accessed on the 24th of July 2022.

Tranomaro Grandidierite Mine is included in the following article:

Ominelite was discovered in the granite rocks along Misen River in Omine Mountains in 1999 and scientifically described in 2002. This mountainous locality is known for its scenic beauty and numerous historical landmarks – temples and shrines scattered in mountains and forests.

The transparent, pale blue grains of ominelite are quite small, not exceeding 5 mm. This gemstone in its chemical composition is similar to another very rare (albeit not THAT rare) gemstone – grandidierite.

Smaller grains of ominelite have been found also in Czechia and Norway.

References

1. Ominelite, mindat.org. Accessed on 25th April 2022.
2. Yoshikuni Hiroi, et al. Ominelite, (Fe,Mg)Al3BSiO9 (Fe2+ analogue of grandidierite), a new mineral fromporphyritic granite in Japan, American Mineralogist, Volume 87, pages 160–170, 2001. Accessed on 25th April 2022.

Misen River ominelite find is included in the following article:

Geology

Red beryl is a unique variety of beryl with an intense raspberry red color. Another excellent and very rare gemstone – pezzottaite – also was considered to be red beryl, but it has a different chemical composition, another form of crystals, and a softer hue. Since 2003 it is recognized as a separate mineral.

Thus, true red beryl is found only in several locations of Utah and New Mexico states in the USA as well as in San Luis Potosi state in Mexico.

The only location in the world where this gemstone is found in a significant amount, is Ruby Violet claims in Wah Wah Mountains.

There these gemstones have formed in the fractures of Blawn Formation rhyolites – volcanic rocks that formed during volcanic eruptions of the middle-late Miocene period some 12 – 8 million years ago.

These fractures formed due to the cooling of the rock – but volcanic gases continued to flow through these fractures for a long time. These gases contained traces of beryllium and other substances. They mixed with the water vapor and on the walls of rock started gradual growth of beryl crystals. The unique color of the crystals was obtained from the manganese. Later fractures were filled with clay.

These unique conditions were quite local – beryls in Ruby Violet claims have been found in 900 by 1900 m large area.

History of Ruby Violet claims

Red beryl was discovered elsewhere – in the Thomas Range some 145 km to the north in 1905. Initially, it was named bixbite – but this name is not used anymore to avoid confusion with another mineral named bixbyite.

The find in Ruby Violet claims was discovered by Lamar Hodges in 1958 during the unsuccessful search for uranium ore.

Hodges family mined red beryls there until 1976 when the mine was purchased by the Harris family. They organized the mining of this extremely expensive gemstone – this was careful mining, searching the stones by hand and working for some months per year when the weather allowed this.

Extensive geological research in this area was done in 1994 – 1996 and the results were promising – under the ground are some more prospective fractured zones. But, even, with the extreme prices of red beryls in the market, digging of increasingly deep mines and sieving of the rock was too daunting and expensive. Thus, in 2001 – 2002 industrial mining activities ceased and mines were recultivated.

Only in the spring of 2021 the mining was restarted in a part of the find.

The most expensive gems?

In fact, no one can tell which gemstone is the most expensive. Some are too rare – only a few crystals exist and are not traded.

But red beryl definitely is multiple times more expensive than diamonds of similar size.

It is a beautiful and noble gemstone. Contrary to most gemstones, red beryl does not need artificial improvements, such as heating and irradiation. But the main reason for its extreme price is the rarity.

Many of the red beryls are not available and not known to a wider public (also a common thing in the premium gemstone market) but it is assessed that there are less than 300 faceted red beryls that are carat-sized or larger. The largest faceted red beryl is 4.5 ct large. The largest raw crystals were up to 5 cm long.

References

1. Red Beryl, mindat.org. Accessed on 8th February 2022.
2. Ruby Violet claims, mindat.org. Accessed on 8th February 2022.
3. James E. Shigley, Timothy J. Thompson, and Jeffrey D. Keith. Red Beryl from Utah: A Review and Update, Gems & Gemology, Vol. 39, No. 4, 2003. Accessed on 8th February 2022.

Ruby Violet claims are included in the following article:

History of Benitoite Gem Mine

The story of Benitoite Gem Mine started in 1907 with James M. Couch – a Californian rancher who decided to prospect in the Mount Diablo range with an aim to find copper or cinnabar. Once, after a few days of research near his campsite, James noticed an exposure with blue crystals. The ground below this exposure was covered with thousands of these blue crystals. Crystals had an intense blue color, they were transparent and glittering – there were no doubts that this is a valuable find. When he managed to go through a bush, James found even more – a small cave that was lined with thousands of these gorgeous crystals (this natural wonder, unfortunately, was dynamited later in an unsuccessful attempt to get the crystals). The excited miner gathered pockets full of these crystals and rushed to tell about his find.

It was not clear what kind of stone this is. It looked like sapphire, one jeweler considered this to be blue obsidian. The prospectors sent the samples to the University of California, Berkeley. Only here geologist George Louderback found out that this is a newly discovered mineral. He named it benitoite after the site of its find near the headwaters of the San Benito River.

Later James Couch was tricked out of the ownership of the Benitoite Gem Mine. The mine was worked by R. W. Dallas, who ordered to make a tunnel through the outcrop. In later years the owners of the mines changed, and many stones were taken also by the collectors and just people who liked to beautify their gardens with large chunks of unusual rocks.

For decades the mining was brutal and nearly all gems were lost in the process – pulverized and otherwise damaged. Only much later it was discovered that hydrochloric acid eats away other materials and intact crystals of benitoite can be obtained.

It is estimated that there are no commercially valuable veins of these crystals left (although no one knows this for sure) and in 2005 the mine was opened to the public. Now the visitors are purchasing fairly expensive tickets to enter the park. Nevertheless, large and beautiful crystals still are found here.

Benitoite is a state gemstone of California since 1985.

The bluest gemstone?

Benitoite is one of the very few gemstones in the world which has a naturally intense blue color – most of the others (e.g. tanzanite, sapphire) in most cases need heating to excel the color. Stones have a noble sapphire blue color, although there are also colorless and pink samples.

This stone has also quite an impressive index of refraction – it is one of the brightest, fieriest gemstones, surpassing diamonds in this respect.

This mineral forms beautiful crystals of a rare form with five points. Sometimes is found an even rarer star-shaped form with 6 points – there have been found approximately 24 pieces of such benitoite crystals.

Benitoite can be fairly easily identified by ultraviolet light – then it glows in a bright blue to white color.

The rarest and most expensive gemstone?

This stone is found in several places around the world but stones of gem quality are found only in one site in California – Benitoite Gem Mine. Some 7 – 8 km to the northwest is one more find – Junilla mine, but only a few specimens of gem quality have been found there. Elsewhere are found either very small crystals or just traces of this mineral.

It has been assessed that between 1907 and 2003 only some 10,000 carats of this gem have been cut and polished. Benitoite of high quality can be more expensive than diamonds, emeralds, or rubies – the price may exceed 10 000 USD per carat!

Together with benitoite are found other very rare minerals – neptunite (beautiful as well!), joaquinite-(Ce), and others.

Everyone can visit the mine and look for the gems himself – on weekends California State Gem Mine is open for visitors and people can search for the stones themselves – and, according to the site visitors, there is much fun and unexpected excitement.

References

1. Benitoite, mindat.org. Page accessed in the 29th January 2019.
2. George Davis Louderback, Benitoite, a New California Gem Mineral. University of California Publications, Bulletin of the Departments of Geology. Vol. 5. pp. 149-153. 1907. Page accessed in the 29th January 2019.
3. California State Gem Mine. Page accessed in the 29th January 2019.
4. The Benitoite Story: California’s State Gemstone. Page accessed in the 30th January 2019.
5. Benitoite Gem Mine, San Benito County, California. Page accessed in the 30th January 2019.

Benitoite Gem Mine are included in the following articles:

History

Maybe one day there will be made a series about tanzanite. An attempt at the scenario by Wondermondo:

The first episode: “False start”

In January 1967 young Maasai man Ndugu Jumanne Ngoma was going to visit his relatives in Kiteto village. As he crossed the low Merelani Hills, he noticed something unusual – blue, transparent gems. He was not in a hurry – thus he stopped and started to pick up these stones. Over the course of several hours, he collected some 5 kilograms of these natural wonders. The value of this find today would be at least one-two million US dollars.

When Ndugu reached Kiteto, his friends advised him to take a bus and go to Nairobi to sell the blue stones in the gem market. There he definitely will get better profit than in the nearby Arusha town.

Thus Ndugu borrowed some money and went to Nairobi. He found an office of gemstone dealers, went in, and showed the gems. “Leave them here, we will determine their value (if any) and will send an answer to you somewhat later” – said dealers, and the simple country boy agreed – just asked for some money to return home.

It seems, these dealers still are busy trying to find out the value of these stones, and Ndugu (if he is in good health) still is waiting for the message from Nairobi…

The second episode: “It begins”

In the same January 1967, another Maasai man Ali Juuyawatu noticed a cluster of deep blue crystals on the ridge of Merelani Hills. He told about this find to tailor and gold prospector, Portuguese Manuel d’Souza, or, as he was known among locals – Mad Manuel.

Mad Manuel picked up these stones – they definitely looked interesting, although it was not clear what kind of mineral it is and what could be its value. Stones looked like sapphires but had an unusually vibrant color.

Manuel showed the stones to geologist John Saul but the latter also could not determine them and decided to send the stones to his father, another geologist Hyman Saul in New York. Saul-elder brought stones across the street to the Gemological Institute of America and specialists there determined that this mineral is zoisite.

In the meantime, several more geologists in Tanzania received samples of this stone and their decision was the same – this is a very unusual variety of zoisite.

The third episode: “Tiffany”

International jewelry giant “Tiffany & Co” noticed these blue stones early. And they – gem cutters, designers, marketing specialists, and, of course, managers – acted fast. In 1968 consumers were introduced to a new, beautiful gemstone named “tanzanite” through a sophisticated marketing campaign.

In fact, geologists initially called the stone simply “blue zoisite”. Jewelers at Tiffany were not happy about this – after all, this sounds a bit like “blue suicide”. Try to sell something with such a name!

Meanwhile, the country of origin – Tanzania has a beautiful, tuneful name. Thus – tanzanite! The marketing campaign of Tiffany declared that this is the most beautiful gem discovered over the last 2,000 years, and stones were included in beautifully crafted rings, necklaces, and brooches. This definitely was a big success for “Tiffany & Co”, well-timed and well-executed. Tanzanite is one of the main gemstones in Tiffany’s jewelry up to this day.

The fourth episode: “Mad times in Merelani Hills”

People headed towards Merelani Hills. We have heard these stories – whether this is a gold rush in Alaska in the 19th century or the mining of diamonds in West Africa now, human nature stays the same. Thousands and thousands of people were digging through the cliffs and dust of Merelani Hills in 1967 – 1971. Everything of value disappeared from the surface of hills in some months’ time and people started to dig deeper in the ground for the next stones. They were disturbing each other, pits and shafts frequently collapsed, and most did not find anything and were increasingly irritated. Conflicts were commonplace, just as theft and heavier crime.

Tanzanian government interfered in 1971 (by that time some 2 million carats of gemstone were mined) and nationalized the mines. But this did not change much – the chaos in Merelani Hills continued. Sometimes up to 30 000 people were working side by side in this small plot of Tanzania and in total, some 70 000 people earn their income thanks to the tanzanite.

The fifth episode: “The big guys know it better”

In 1990 the find of tanzanite was divided into four blocks – A, B, C, and D, where the mining rights in B and D were given to local miners, but A and C – to large operators (now small miners are also in A block).

Since 2004 block C is operated by the company “TanzaniteOne Mining Limited” – a mining company that strives to be a showcase of ethical business. And, indeed, mines (up to 800 meters deep!) of this company are a lot more safe and comfortable than in the other sectors, workers are better protected socially, tanzanite stones are getting added value (sorting, cutting) in their home country – Tanzania.

In order to promote knowledge about the real value of tanzanite “TanzaniteOne” has created a subsidiary non-profit organization “The Tanzanite Foundation” which strives to improve the living conditions of the local community and, especially, workers in tanzanite mines. Nevertheless, local miners, which work outside the “TanzaniteOne” sector, consider that “The Tanzanite Foundation” is a typical case of astroturfing – an artificially created pseudo-civic organization that imitates socially important activities in order to retain the control of large companies over natural resources.

What about the other – sectors of local miners? Not much has changed except that mines are going deeper and deeper and work is harder and harder. One needs to descend hundreds of meters into narrow and dangerous ratholes and work through dust and cliffs in search of increasingly rare tanzanite crystals.

The mines are gradually exhausted. In 2011 “TanzaniteOne” mined some 2.5 million carats and earned 24 million USD. Since then the amount of tanzanite and profits are falling, and the number of workers is decreased. Mines go deeper and deeper and it is increasingly expensive to maintain them. Thus it is expected that around 2030 – 2040 the mining may stop here altogether.

Geology and chemistry

Zoisite

Tanzanite is a variety of a rather common mineral – zoisite.

Zoisite also can form beautiful, transparent crystals which are colorless, greenish, grey, or brown. Fine gems are cut from zoisite too – but the value of other varieties is not as high as the tanzanite value.

Blue zoisite of Merelani Hills

Only in one place on Earth is found zoisite in wonderful, deep blue color – this is in Merelani Hills, Tanzania (although some ink-blue gems of zoisite were found also in the Tsavo region, Kenya). This zoisite – tanzanite – is found in a small area that is just 7 by 2 km large. Tanzanite is at least 1000 times rarer than a diamond.

This gemstone has formed in metamorphic rocks and is mined together with several more beautiful gemstones, such as chrome diopside, tsavorite, blue apatite, grass-green tremolite, and another unique gemstone – axinite-(Mg). In Merelani Hills are found the most beautiful crystals of graphite in the world – one more highly valued collector’s item.

Mines in Merelani Hills have been very rich and the quality of mined jewels does not decrease up to this day. Thus, from 1995 to 2005 there were mined some 39 tons of tanzanite.

The largest rough piece of tanzanite was found in 2005. The weight of this stone was more than 3 kg: 16,839 carats. It was named “The Mawenzi” – after one of the summits of nearby Kilimanjaro.

Heat treatment for color

Rough tanzanite is reddish-brown to colorless and there is needed heat treatment to bring out the beautiful blue-violet color. There is needed heat of some 370 – 390 °C for some 30 minutes. The process is risky: if a crystal has some cracks, it shatters in the process.

Sometimes nature creates these blue crystals. Initially, in 1967 there were found beautiful blue crystals on the ground surface. These crystals, most likely, were heated by forest fires. But also deeper in the mines in some places crystals are blue – these pieces of zoisite, most likely, got heat from some geological processes in the past.

Tanzanite by far is not the only gemstone that is heated. For example, some 90% of sapphires, most of the amethysts, ruby, aquamarine, and, other stones are heated as well. Sapphires can be heated at much higher temperatures for weeks, totally transforming the stone.

Thus specialists do not consider the comparatively mild heating of tanzanite to be “cheating” – especially if this happens naturally as well.

Miraculous color effects

The unusual blue color is created by trace amounts of vanadium and/or chromium – similar as in the case of extremely rare blue garnets (see blue garnets of Bekily, Madagascar).

Tanzanite has a very unusual property – trichroism. This means that a crystal of tanzanite changes its color depending on the direction of how one looks. From one side it may be deep blue, from other – purple, and from another – burgundy. There happen to be other colors too: indigo, cyan, green, yellow.

In fluorescent light, the blue color is more intense, in incandescent light the violet hues are more pronounced.

After the heat treatment stone is dichroic – color changes between purple and indigo or blue. Heat treatment removes the brown – burgundy color.

Rarely the stone gets a set of green and blue color. Such stones have much less value as gems, but collectors love them – these stones are especially rare.

The most valuable – deep blue color – is only in 1% of tanzanite samples.

High value

Thus far there has not been noticed synthetic tanzanite or high-quality imitations. This again is rare – and increases the value of the stone even more: if something is sold as tanzanite, a client can be sure that this IS tanzanite.

The price of the highest valued tanzanites may reach 1200 USD per carat and it continues to increase. Tanzanite is also one of the highest valued stones for collectors – even in the largest collections tanzanite takes the central role. Many specialists consider that this is the noblest of all blue gemstones, surpassing even the centuries-long fame of sapphire.

References

1. Tanzanite Foundation. Page accessed in the 1st December 2018.
2. Working the Blueseam: The Tanzanite Mines of Merelani. Now this is a great website! Accessed in the 1st December 2018.

Merelani Hills are included in the following articles:

Legendary geologists

Geologists in Russia have been very special people. Nobody else has crisscrossed the incredibly large area of this country, nobody else knows as much about nature’s secrets here. In the eyes of many common people, geologists are somewhat different – they seem to be away from the political turmoil and hypocrisy, leading to intellectually rewarding and at the same time – physically demanding life far away from civilization. Of course, the reality often is different – but such legends may have some truth in them. Discoverers of charoite: Vladimir Ditmar, Vera Rogova, and Yury Rogov are some of such legendary geologists.

Vladimir Ditmar

The first known person to see charoite was Vladimir Ditmar – an outstanding, adventurous geologist who managed to fill in quite a few white spots on the map of Siberia and the Far East. He and his team researched the Murun massif and in 1948 Ditmar noticed the unusual color of some stones in the bed of one stream – now called the Ditmar stream. He did not have a possibility to research it and just mentioned it as a “cummingtonite slate”.

Before this local people did not notice this unusual stone. They visited the hills only in wintertime. The weathered surface of charoite is not attractive – it looks just like one more common rock.

Vera Rogova and Yury Rogov

For a while, the unusual rocks were forgotten. But in 1960 geologists led by Yury Rogov returned to this area. Once Yuri decided to look at the old shack of Ditmar – and found an unusual stone next to it. He chipped off a piece of this stone to bring it back to his wife – mineralogist Vera Rogova.

Vera immediately noticed a yellow mineral in this sample and correctly determined that this is a new mineral to the science – later it was named tinaksite. But the most attractive feature of this stone was another mineral in gaudy lavender color – a very rare hue in mineralogy. Geologists at first could not believe that such an attractive feature could be something new.

Work in the exciting Murun massif continued and geologists made one important discovery after another. Nearby they found rich ores of uranium and other valuable materials, mineralogists discovered new minerals.

Only in 1973, some gemmologists noticed the outstanding properties of lavender-colored stones, and there appeared first artworks made from it. Serious research started and in 1977 scientific community approved the new mineral, which was named: charoite. Vera Rogova gave this name after the nearby river Chara… but she did not forget about the other meaning of this word. In Russian “chara” means charm, wonder.

Murun massif

The whole Murun massif is a unique natural monument with a very complex geological situation and numerous unique and very rare minerals and rocks. In this area are found some 200 diverse minerals, many of them rare and even unique to this area. Only here are found such minerals as tinaksite, charoite, tokkoite, frankamenite, and murunskite. This remote location is like a paradise for collectors of minerals and gems.

The genesis of this unique geological monument is not entirely clear. It is known that this is a contact of syenite and limestone deposits. The unusually high content of calcium, as well as barium, strontium, zirconium, and other elements, led to extreme mineralogical diversity.

Charoite

Charoite is found in an area of some 10 – 12 km² along the southern margin of the Little Murun intrusion – an especially interesting part of the Murun massif. It has not been found anywhere else on our planet.

This mineral is translucent and massive – thus it is not exactly gemstone. But it has a very unusual, bright lavender-purple color and pearly luster – charoite looks almost like an artificial, visually enhanced material. Also – the stone is quite hardy. Thus it can serve as exclusive material for jewelry, as well as for small utensils – such as cups, bowls, frames, and cases.

Chemical composition of charoite is quite complex and its research took several years. There are different ways to represent it, and one is:

(K,Sr)_15-16(Ca,Na)₃₂[Si₆O₁₁(O,OH)₆]₂[Si₁₂O₁₈(O,OH)₁₂]₂[Si₁₇O₂₅(O,OH)₁₈]₂(OH,F)₄ · ~3H₂O

Mining

Mining charoite is quite hard work. It is nearly impossible to transport heavy machinery to this far away location, where some 1000 km needs to be made without any proper roads, reaching the height of 1.5 km above sea level. The sturdy rock cannot be blown up – this would damage the unique mine forever. Thus the stone is mined carefully and rather slowly by other methods, involving much handwork.

The known stock of charoite in this area is more than 100 000 tons. The Sakha Republic has limited the mining of charoite to 100 tons per year – thus the mines will be used for a long time and the mined material would be used carefully, for high-value items. On the side of Irkutsk Oblast charoite currently is not mined. The price of raw charoite is around 30 – 700 USD per kg, especially valuable is the charoite which was mined in the 1970ies.

It is highly possible that there is produced fake charoite as well.

References

1. Рогова Вера, История открытия чароита и других минералов, Petrographica.ru. 7 November 2010. Page accessed in the 28th November 2018.
2. Images of the mining process and the mine, 11th September 2010. Page accessed in the 28th November 2018.

Sireneviy Kamen is included in the following articles:

Garnets – colorful gemstones

Garnets are some of the most popular gemstones. These stones are hard, with gorgeous and lovely natural crystals and diverse, bright colors. Group of garnet minerals includes some 25 – 30 minerals with a very similar chemical structure – just the kind of metallic elements changes in the chemical formula. Some garnets include magnesium and aluminum (pyrope), some – calcium and chromium (uvarovite), etc.

Garnets come in all colors. Best known might be the deep red and purple pyropes and almandines, bright orange spessartine and light-green grossular, as well as emerald-colored demantoid (a type of andradite) and bright green uvarovite. Schorlomite is black, several types of garnets are rose-colored, brown, and yellow. Very rare is also colorless garnet (leuco garnet), a rare kind of grossular which can be found in Canada, Mexico, Tanzania, and Burma.

But on the jewelry market, there were not available blue garnets. Until 1997 – 1998.

Bekily blue garnets

Around 1997 there started mining of beautiful garnets north of Bekily, a poor and remote area in the southern part of Madagascar. Searching (and finding!) valuable gemstones is nothing new in Madagascar – this island is very rich with top-class gems and here have been found quite unusual gemstones, such as grandidierite.

At first, prospectors thought that they discovered gem-quality alexandrite – a very valuable color-changing gemstone. To their surprise, this was something even rarer – blue garnet.

Such unusual daylight color amazed gemmologists – blue garnets were something new to them. This was not one or two occasional stones – specialists back then obtained some 160 samples of these unique stones (1.).

Stones were obtained in the gemstone market in Bekily – the location of their find was not disclosed. Now there are rumors that the find has exhausted already in 1999 (2.) but the political and social unrest in the country could also be blamed for this. From time to time some color change garnets still come from these mines but clear blue ones are missing now and in the market can be seen the same stones from the late 1990ies which tend to become more and more expensive with each resale.

The unusual change of colors

These blue garnets are a mix between pyrope and spessartine, with small amounts of almandine and grossular contents. Their color-changing scheme is as follows: in normal daylight, they are blue (the rare best samples) or grayish-blue. In white light (e.g. from LED lamps) they are bright blue. In the usual artificial light, they become red – reddish-purple. Color change, most likely, is created by unusually high amounts of V₂O₃ (vanadium oxide) and some amount of chromium oxide.

Most of the “blue” garnets from Bekily are not really blue but rather grey-bluish, also green-blue. But there are some clear blue specimens. Even rarer are well-formed crystals of blue garnets – prospectors are finding just a shambles of crystals. But at least two crystals of pure blue garnets exist (3.).

Size and price

These stones were small – the largest gem-quality blue garnet in 1999 was just 9.5 carats large. Cut stones are much smaller – 0.1 – 0.8 carats.

Larger blue garnets with a color-change effect are very expensive, with a price exceeding USD 1,500 per carat. But for this high price garnets need to be large and pure blue without the gray or green color. Nevertheless, the more common alexandrite with similar properties could be more expensive.

Are Bekily blue garnets unique?

Color-change garnets from Sri Lanka (finds in Embilipitiya and Athiliwewa) and Tanzania (finds in Umba and Tunduru) have been known since 1979. This always has been a rarity, with some occasional bluish-greenish garnets among them.

Blue garnets, similar to Bekily blue garnets, have been reported in Kenya, Taita-Taveta County since 2009. Nevertheless, the unique stones from the vicinities of Bekily are the main commercially available blue garnets.

References

1. Karl Schmetzer and Heinz-Jürgen Bernhardt, Garnets from Madagascar With a Color Change of Blue-Green to Purple. Gems&Gemology, Winter 1999, page accessed on the 26th November 2018.
2. Ambahatany. Mindat.org, page accessed on the 26th November 2018.
3. Farbwechselnde und blaue Granate. Mineralienatlas – Fossilienatlas. Page accessed in the 26th November 2018. Images of blue garnet crystals!

Blue garnets of Bekily are included in the following lists and articles: