Charoite - a chance discoveryLast Updated: 13th Jan 2021
By David Carter
Vladimir Georgievich Ditmar was a Russian scientist born on 23rd July 1903 in Stary Oskol, Belgorod Oblast, Russia. He died on 27th March 1967 in Blagoveshchensk, Amur Oblast, Russia. During his career he carried out geological fieldwork in the remote Aldan Shield geological region of Yakutia, officially known as the Sakha Republic (Yakutia). This region is an exposed basement of the Siberian Craton which is an old and stable part of the continental lithosphere, which consists of the Earth's two topmost layers, the crust and the uppermost mantle. In the post war years after the Second World War, Russia was in the process of rebuilding its economy and the nation as a whole still had many difficulties. Life was hard, not least for geologists who were sent to explore remote areas searching for valuable mineral resources. Exploration and research in the Aldan Shield is still pretty infrequent even today, often determined by the remote and inhospitable environment, with access extremely limited for those reasons. Exploration does take place however, both for purely scientific purposes and also because the area has incredible wealth potential from its rich mineral resources. Ditmar spent his time exploring step-by-step the uninhabited taiga and mountainous expanses in the harsh conditions of the far north. He spent three years from 1956 surveying and studying the Murunskii Massif, which is an alkaline complex located on the ternary boundary of Irkutskaya Oblast, Sakha Republic and Chitinskaya Oblast, at the confluence and in the drainage divide of the Chara and Tokko rivers, in the westernmost part of the Aldan Shield. Ditmar lived there in a little squat hut constructed to protect him from the elements whilst he carried out lengthy research at the remote locality with a small detachment of fellow geologists from Leningrad. The Ditmar detachment were subsequently recalled in 1959 when a different geological study was despatched to the area.
In 1960, geologist Yuri Gavrilovich Rogov and a team of scientists and technicians returned to the small Ditmar camp. The stream and glen at the location had been marked by Ditmar on geological maps as ‘Ditmarovsky’ and the locations of lumps of weathered lilac rock were also marked on those maps. The youthful team of geologists, in larger numbers than the previous expedition, worked long hours as they explored the area, but they were keen with a thirst for discovery. A village was built with an airfield in the nearby forest and they organised the construction of a mineralogical laboratory and also a rock grinding workshop to process the complex material they were finding. In 1960 Yuri, along with his fellow geologist and technician Volodya Nikitich, brought samples of lilac rocks they had found near Ditmar’s old shack to the on-site mineralogical lab. Within this lilac mass, along with dark green aegirine, they saw elongated prismatic crystals of an unidentified honey-yellow mineral. One of the mineralogists in the team Vera Parfentievna Rogova, along with her lab assistant Katya Fedorova, examined the specimen and Vera suspected that it was a previously undiscovered mineral. She was correct in her supposition because the mineral was subsequently analysed and officially recognised as a new mineral. It was named tinaksite in 1965, the name derived from its composition: titanium (Ti), sodium (Na) potassium (K) and silicon (Si).
However, that rock sample did also seem to have another distinctive feature contained within the body of the specimen which was rather attractive. It was lilac in colour, a comparatively rare hue in mineralogy. The geologists perhaps did not initially believe that such a pleasing feature could be something new and it was disregarded whilst they continued with more demanding and engaging work around the Aldan Shield. Several important discoveries were made by the geologists as a result of their ongoing exploration and further research. Nearby they found rich ores of uranium and other valuable materials. Mineralogists in the team also discovered new minerals. Overall, the whole of the Murunskii Massif is itself a quite unique natural monument formed by very complex geological circumstances, the genesis of which to this day is still not entirely clear or understood. What is known is that there’s a contact of syenite and limestone deposits and the unusually high content of calcium, as well as barium, strontium, zirconium and other elements, led to some extreme mineralogical diversity. The Aldan Shield produces numerous distinctive minerals and rocks (such as charoite, tinaksite, arkansite, frankamenite, murunskite, tausonite, tokkoite, yuksporite, etc.), many of them rare and unique to that particular area. The remote location is like a paradise for collectors of minerals and gems!
It was some years after the expedition and discovery of tinaksite, 1973 in fact, that gemmologists first realised the potential of the lilac coloured stones that had previously been recovered by geologists from those early Aldan Shield explorations. When cut and polished the material displayed an oily to pearly lustre and it presented wonderful, often swirling and dappled, feather-like, violet to lavender patterns.
When publishing an article subsequently about the discovery of tinaksite, it was necessary for Vera Rogova to indicate which minerals accompanied it. Since the composition of the lilac mineral is close to canasite and it is in the same group with it, it was simply called canasite so as not to delay the publication of the tinaksite article. Therefore, initially the lilac stone was known as canasite. However, after more detailed analysis and further research which differentiated the lilac stone from canasite it became necessary to give the new material its own name. Vera pondered for some time over various geographical related names associated with the nearest mountains, rivers, and lakes where the mineral was discovered. The association of the name with the Chara River prevailed, along with the fact that coincidentally the word ‘chary’ in Russian means enchantment which Vera thought apt as an expression for the the enchanting lilac stone. The only doubt she had was that the Chara River is some 43 miles away from the actual place of discovery. However, she came to the conclusion that minerals are often named for the initial place they were first discovered, yet they may also then be subsequently found in far away places elsewhere or even in different countries. And so it was that the name ‘Charoite’ was proposed and eventually approved for the new mineral by the IMA (International Mineralogical Association) in 1977. In Russia, charoite is referred to as ‘sirenevyi kamen’ (cиреневый kамень), meaning lilac stone. To this day charoite has not been found anywhere else in the world.
Link to the charoite mineral page on Mindat: Charoite
Charoite occurs within a syenite massif at the location, in metasomatic rocks, formed at alternatively 400°C (Rogova, 1978) or 200-250°C ( Biryukov and Berdnikov, 1992) that are enriched with potassium at the contact with limestone in the massif.
The main chemical components of chariote-bearing rocks are potassium (K), sodium (Na), calcium (Ca), silicon (Si) and water (H2O). The secondary components are barium (Ba), strontium (Sr), manganese (Mn), and titanium (Ti). The presence of iron (Fe), magnesium (Mg), aluminium (Al), rubidium (Rb), thorium (Th), tantalum (Ta), cerium (Ce), zirconium (Zr), etc. are noted in trace amounts.
The paragenesis of charoite rocks (charoite, canasite, tinaksite, frankamenite, miserite, etc.) explains the fact that so called ‘pure’ charoite doesn’t actually occur in nature. Close accretion and intergrowth of phenocryst minerals (aegirine, tinaksite, microcline, quartz, arfvedsonite, apophyllite, frankamenite, etc.) is observed in charoite, therefore the mineral has a very complex chemical composition. The IMA chemical formula for charoite is:
(K,Sr,Ba,Mn)15-16(Ca,Na)32[Si70(O,OH)180](OH,F)4 · nH2O
Charoite is a durable and reasonably hardy stone that is capable of being sculpted and heavily polished so it therefore has several potentially profitable applications for jewellery, decorative and ornamental use. However, mining of charoite is hard work and the source is situated nearly a mile above sea level and located over 600 miles from any proper roads. It is near impossible to transport heavy machinery to the far away location and using explosives isn’t really practical because it would damage the mine, so the stone is extracted carefully and quite slowly by other methods, much of it by hand. Whilst there are estimated stocks amounting to many thousands of tons of charoite in the area, the Sakha Republic has put a limit on the amount that can be mined at just 100 tons per year, in the hope that this not only ensures a long production life for the mine, but also keeps demand strong and value high. However, that has seemingly also increased the possibility for ‘fake’ charoite finished items, such as low grade polished purple Chinese fluorite to enter the marketplace too!
Information researched from various sources including:
Рогова Вера, “История открытия чароита и других минералов”, Petrographica.ru.
(Rogova Vera, “History of the discovery of charoite and other minerals”, Petrographica.ru.)
Юрий Рогов: биография, творчество, карьера, личная жизнь
(Yuri Rogov: biography, creativity, career, personal life)
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