Emeralds of the Urals

Some History

The emerald saga started with a man named Maxim Stefanovich Kozhevnikov, of Beloyarsk, who found a few green crystals in the roots of a tree on the bank of the Tokovaya River. He took the stones to Yekaterinburg to sell them, and a small sample was delivered to Yakov Kokovin, commander of the Yekaterinburg Imperial Lapidary Manufactory and the Gornoshitovsky Marble Factory.

Kokovin believed that the stone was emerald. Immediately, on 21 January 1831, he traveled with the workers and necessary tools to the place indicated by Maxim Kozhevnikov on the Tokovaya River. Despite the snow and cold, he started prospecting and, on 23 January 1831, a mica vein was found. While following it, several crystals of good quality emerald were discovered. This day is considered to be the date of the discovery of the Ural emerald.

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The saga of emeralds begins at the Tokovaya River, where Stefanovich Kozhenvnikov found the first green crystals trapped in the root of a tree

Further events developed very rapidly. Soon after the extraction of the first emeralds, the best samples were sent to Yekaterinburg, where they were cut at the Yekaterinburg Imperial lapidary manufactory, and later presented to the vice-president of the Cabinet of His Imperial Majesty. Almost all known emerald deposits were discovered between 1831 and 1839: Troitsky Mine (now Pervomayskoye) in 1832; Mariinsky Mine (now Malyshevskoe) in 1933; Hitny Mine (now Red Army Mine) in 1838. For the discovery of eme-ralds, Maxim Kozhevnikov was awarded a cash prize of 200 rubles. Yakov Kokovin was awarded the Order of St. Vladimir of the 4th Degree, which gave the right of hereditary nobility.

01The Yekaterinburg Imperial Lapidary Manufactory in the center of the city, next to a mid-19th century church

The fate of the emerald pioneers was, however, rather tragic. Maxim Kozhevnikov (born in 1799) died in 1865 of tuberculosis, which he developed in the mines. He was buried at the Beloyarsk cemetery, but his gravesite is unknown.

Yakov Kokovin (born in 1874), was a descendant of the Ural stonecutters. Through his work and talent, he achieved nobility and a high rank—commander of the Yekaterinburg Imperial Lapidary Factory and the Gornoshitovsky Marble Plant. He was a great connoisseur of gems from the Urals, and discovered deposits of jasper, rhodonite and emery (abrasive). From 1831 to 1835, Kokovin supervised the exploration and extraction of emeralds at the Sretenskoye Mine, where a unique 2226-gram emerald was found. Known as the Emerald of Kochubei, it is currently in Moscow at the Fersman Mineralogical Museum. Another famous his-torical stone, known as the Izumrud Kokovina, a clear and pure 400-gram crystal was also from this mine, but its fate today remains unknown. The Kokovina emerald was found at Sretenskoye in 1834 and sent to St. Petersburg. Alas, the Vice-President of the Department of Udelov, Count L. A. Perovski, stole the stone and accused Kokovin of the crime.

 In 1835, Kokovin was arrested and imprisoned and, upon his release in 1838, seriously ill, he was deprived of his rank. He died in 1840. The Kokovina disappeared, and is most likely in a private collection outside of Russia.

2View of the Sretenskoye (now Sverdlovskoye) Mine in 2000

3.1Old mine shafts from the early 19th century, which were discovered in the early 21st century

From 1835 to 1839, extensive work was conducted at the emerald mines under the guidance of I. I. Vein. Mining activities gradually decreased, and by 1852, were nearly completely suspended because of strong water inflow. The ​emerald mine area was studied from 1853 to 1855 by K. I. Greving, who had a negative opinion about the work that was suspended until 1860.

In 1860-1861, the studies were carried out by P. I. Miklashevsky who, like Greving, gave a negative assessment of the mines and recommended that they be leased. So, from 1862 to 1899, the mines transferred from one private tenant to another and were not studied at all. From 1899 to 1917, the mines were moved to the concession of the Anglo-French New Emeralds Company.

The emerald mines were nationalized in 1919 and, in 1923 transferred to the Ruskie Samocvety trust. In 1930, it was established that emerald mines were promising for industrial beryl, which was the basis for an extremely important event. On August 29, 1931, the mines were transferred to the Soyuzredmet Association, which changed the orientation. Emerald mines then become a source of beryllium ore, which was of strategic importance and represented the main value of the deposit. Emeralds receded into the background until the early 1970s. From 1999 to 2007, the mine was owned by Zelenkamen, which attracted as an investor the Tsar Emerald Corporation (Canada) in 2004. The corporation’s president, Donald Padgett, managed to convince the regional authorities that he intended to invest US$12 million in developing a joint venture. Since 2005, active restoration of production began, although not at the pace that was earlier announced. Nevertheless, the lifting complex, the main ventilation fan, the laying complex and drainage installations were repaired. Basically, the enterprise only processed the mine tailings extracted in previous years. In the opinion of the Ministry of Natural Resources, there were repeated violations of subsoil-use conditions and after many inspections and proceedings, the Ministry revoked the company's license in 2008. In the same year, the deposit was transferred to the Kaliningrad Amber Factory, owned by the state corporation Rostec. From 2008 to 2011, the Kaliningrad Amber Factory carried out repairs and preparatory work at the mine. In June 2011, it received a license for subsoil use until 2031. Since December 2011, emerald raw materials have been extracted and the following year, processing took place at the emerald recovery plant.

The Current State of the Malysheva Mine

For 25 years (1991 to 2016) the mine was not actively developed and technology was frozen at the 1990s level. At the end of 2015, almost the entire management of the Malysheva Mine was replaced, and Evgeny Vasilevsky was appointed director.

4Director of the Malysheva Mine, Evgeny Vasilevsky, in an underground section of the mine

The new team installed a new operational strategy, including developing the emerald cluster. Modern technologies were adopted for both mining and ore processing. After extraction, the emeralds are sorted according to purity, color and size.

5View looking down one of the tunnels of the Malysheva Mine

6Concentrators at the Malysheva Mine. The emeralds are manually selected from the conveyer belts

Major changes have also taken place in security. It should be noted that emerald theft at the mine and during the pro-cessing stage is a very significant problem. Theft has a long history in the Urals, starting with emerald mining in the Urals in 1834. There is still illegal mining both outside the mine area and at all stages of the technological process. According to experts, illegal production may be twice that of official production. The new security efforts have yielded tangible results over the last two years.

 Although it is expected that the explored reserves will last for many years, geological work is being expanded in search of new fields.

Brief Geological Survey of the District

Geologically, the emerald area is located at the junction of the Murzinsk-Aduisk anticlinorium and the Asbestian synclinorium. This border position caused the complexity of the tectonic environment and the spatial overlapping of different genetic formations. In the geological-petrographic respect, the region is divided into three zones: east, west and central. The eastern zone is composed of basic and ultrabasic rocks of the Asbestian intrusion, represented by peridotites, dunites, gabbros, pyroxenites. By the time of formation, they belonged to the lower carbon. The Asbestian intrusion is bordered by a small array of granodiorites and diorites of the Middle Devonian age.

7The western zone is composed of the Aduisk granite massif of the Permian age. Its central part is represented by small- and medium-grained biotite and two-mica granites. Pegmatoid and medium-grained muscovite granites with a considerable number of veins of pegmatites and amphibolite xenoliths are developed in the exocontact zone. 

7.1The central zone is composed of the most ancient primary sedimentary rocks of the Silurian-Ordovician, metamorphosed zonally under conditions from amphibolite to green-schist facies metamorphism. In the petrographic sense, the stratum is represented by carbonaceous-siliceous schists, quartzites, amphibolites, and products of metamorphism of ultrabasites, serpentinites, talc and chloritetalc schists.

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The whole stratum is broken by a large number of dyorite porphyritic dykes. The stratum is enclosing for emerald and beryllium tools, and can be traced along a strike for 25 km at a thickness of 0.5 to 1.5 km. Stretching of the strata is close to the meridional, with the eastern fall at 50o to 85o angles. Ore bodies in the deposits are represented by two main types: veins and metasomatic complexes. Among the metasomatic complexes developing under the action of pneumatolytic-hydrothermal solutions—enriched with po-tassium, sodium, fluorine, beryllium and other elements—the following are distinguished: greisens over granites and micaceous complexes on ultrabasites.

Precious stones in the deposits are mainly associated with mica complexes. Slyudite complexes have a zonal structure. The central zone is micaceous, almost monomineral rock at 95% to 99% folded phlogopite. In a subordinate amount are actinolite, chlorite, talc and margarite. Accessory gems (1.0% to 1.5%) are represented by chrome spinels, beryl, phenacite, chrysoberyl and other minerals. The color of the mica varies from greenish gray to brown. It has a small, coarse, scaly structure, a shaly, less non-oriented texture. 

The outer zone of the micaite complexes is represented by talc and talc-tremolite schists. 

 Slyudite complexes have a complex structure with clamps, blowing and numerous apophyses. In plan and section, the micaceous complexes are located in an orderly manner, and can be traced along the dip and strike for hundreds of meters. Most of the mica bodies have a length of up to 50 m at a thickness of 0.1 to 8.0 m, with an average thickness is 0.7 m. Emerald and beryllium mineralization is noted pre-dominantly in mica and localized in the central zone of the phlogopite micaite. Less often emeralds are noted in the talc zone, actinolites, quartz and plagioclasite.

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In addition to the micaceous complexes, pegmatites and beryl-bearing quartz-plagioclase veins are widespread in various rocks. These veins contain only technical beryl, with complete absence of emeralds.

Pegmatites of the mine area belong to the slightly differentiated rare metal type. The most valuable are minerals of tantalum, niobium and beryllium: tantalite-columbite, mona-zite, orthite, thorite, beryl, bertrandite. Pegmatites form vein clusters in some areas, allowing them to be considered as tantalite-columbite deposits.

Quartz-plagioclase veins are composed mainly of plagioclase, quartz and muscovite. In some varieties, a high content of beryl is noted. Minor minerals are represented by fluorite, apatite, topaz, tourmaline, chrysoberyl, phlogopite. Accessory: monazite, xenotime, thorite, corundum, sphene, rutile, etc.

At present, 33 emerald and beryl deposits are within the area (see geological map above). The largest and most interesting is the Mariinsky deposit. 

14Sub-parallel intergrowth of emerald crystals in mica. Sample size is 12.5x9x5 cm. Private collection

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Nodule of emerald-plagioclase composition. Crystal size is 8 cm along the long axis. Ural State Geological Museum

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Chopped emerald nodule (8x5x3 cm). Ural State Geological Museum

Mariinsky Emerald Deposit

The Mariinsky deposit is the largest emerald deposit in Russia. With a few disruptions, the deposit has been in operation for 185 years, since 1833. The Mariinsky field accounts for about 80% of all explored reserves of emeralds and more than 50% of beryllium ore reserves. 

The deposit is located in strongly dislocated talc shales, among which are lenticular bodies of serpentenites, dykes of diorite porphyrites, and bodies of carbonaceous-siliceous shales. There are three major faults in the field: West, Central and Krestovsky. In fracture zones, rocks are prone to tectonic dissection and intensive metasomatic study. The fault zones can be traced along the strike to 1200 m, and the depth from 5 to 70 m.

Dike bodies are spatially associated with fault zones. By the strike and fall of the ore zone, the five largest dikes are traced, the length of which reaches 1150 m, with a thickness of 5 to 100 m. The ore zone is divided into three main vein suites, confined to the same fault zones. The central formation is most saturated with ore bodies and contains 67% of beryllium ore reserves and 91% of emerald reserves.

Saturation with ore bodies with depth varies insignificantly. Only on the northern flank is the excretion of ore bodies at a depth of 220 m. In the central part of the deposit, the ore zone is fixed without signs of wedging to a depth of 490 m. In the southern section and to a depth of 800 m, wedging out of the veins is not observed, and one ore zone is opened at a depth of 1100 m. It should be noted that, at present, the deposit has been worked to a depth of only about 300 m.

Genesis of the Micaceous Complexes

There are two points of view on the genesis of metasomatic complexes with precious stones of the beryllium series. A. Fersman and his followers linked the formation of the micaceous complexes with the processes of desilication of a pegmatite melt enriched with volatile components. The residual part of the melt was separated from the main melt and formed contactreaction zones. Other researchers, Ginzburg AI, Sherstyuk AI and others, refer these complexes to greisen formations by basic and ultrabasic rocks that have arisen under the influence of high-temperature pneumotalitic-hydrothermal solutions. This point of view is more popular. 

20Emerald crystal in mica with a crack healed by micaceous. Crystal size is 9 cm along the long axis. Ural State Geological Museum

Emerald Mineralogy and Gemology

Emerald (Be3Al2[Si6O18] * 0.5H2O) belongs to the beryl group, retaining its basic crystallochemical, physical properties and chemical composition. The Ural emerald is characterized by a green color of varying intensity, from bluish green to dense green, occasionally with a yellowish tinge. The color is explained by the isomorphic replacement of aluminum in the beryl structure by trivalent chromium. The green shade appears even with a content of 0.05% Cr3+, while the most intense color is characteristic of a Cr3+ content of 0.15% to 0.20%. The bluish hue is determined by the ad-mixture of Fe3+, and the yellowish admixture of manganese. By the nature of coloring, there are uniform, zonal and spot-ted color differences.

Uniform color is noted mainly for small crystals. The zonal color of the crystals is more characteristic, and the zones can be oriented both along and across the crystal. Zonal staining by pinacoid is often noted; the densely colored central part is overgrown with almost colorless transparent beryl.

Reverse zonality is also observed. Internal defective zones, sometimes with a milky hue are replaced by transparent or densely colored differences, as well as alternation of colorless and green zones of varying intensity.

11Reverse zonality in emerald crystal (12x7x6 cm). Ural State Geological Museum

Spotty coloring is due to the inclusion of chrome-spinellid grains. Spots of green color have an elliptical shape, and the center of the halo coincides with the grain of the chromo-spinelide. Emerald crystals have a simple prismatic appearance, a combination of a {1010} prism and a pinacoid {0001}. The ratio of the sizes along the axes is from 1: 3 to 1:20. The average size of crystals is 1x1x3 to 1x2x5 cm.

19Emerald junction with fluorite.Sample size is 16x9x9 cm,emerald crystal 9x3x3 cm.Ural State Geological Museum

There are both single crystals and their intergrowths, sometimes forming nests and nodules. Pockets are areas of mica rock, saturated with separated emerald crystals. Pockets sizes reach 0.5 m to 1.5 m along the strike, and emerald crystals are usually oriented along schica mica. Also seen are nodules and round clusters of emerald crystals, emerald-beryl, emerald-plagioclase and emerald-quartz composition. The space between the emerald crystals is plagioclase, quartz and fluorite. Often, emerald crystals are bro-ken by transverse cracks along which a part can be rotated relative to the other around the axis by 30o to 40 o. The cracks are healed by plagioclase, quartz and phlogopite.

The Ural emeralds are characterized by numerous mineral inclusions, which occur in the process of emerald growth. There are many inclusions in emeralds occurring in phlogopite, whose flakes enclose crystals or germinate them.

22A single emerald crystal in mica with numerous inclusions of phlogopite. (16x8x7.5 cm). Private collection

In addition to phlogopite, inclusions of talc, tremolite, actinolite, apatite, fluorite, phenakite, chrysoberyl, tourmaline, monazite, chrompicotite, rutile, titanite, anatase are noted. Emerald crystals enclosed in quartz or plagioclase contain fewer inclusions and their faces are smoother and shinier.

According to the technical specifications adopted in Russia (TU 95 335-88), the main indicators of the quality of cut emeralds are: color, purity, group by weight, type of cut and quality of cut.

Color: depending on the color tone, emeralds are divided into five color groups.

Purity: characterizes the transparency of stones, the pre-sence of gas-liquid and mineral inclusions. Depending on the quantitative manifestation of these parameters, faceted emeralds are divided into three purity groups.

Cabochons are divided into two groups.

For Mass, emeralds are divided into 11 groups.

The enriched (untreated) crystal raw material of emerald, both in color and purity, is divided into three groups for each parameter. By size, each group is also divided into three dimensions: 2–10 mm; 10–20 mm; 20 mm or more.

25Rough emeralds, sizes from 10 to 20 mm

The best emeralds from Russia, both in size and value, are on a par with emeralds from other parts of the world. The 32,750-carat Miner’s Glory emerald, mined by P.P. Bebenov in November 1989 at a depth of 255 m, deserves special attention. The intergrowth of emerald crystals was found in the vein swelling, at the site of conjugation of its several apophysis. It is the largest specimen in the history of Russian emerald mines. Another significant find is the 5860-carat President emerald (1172 grams) found in August 1993.

Conclusion

The Ural emerald mine area is a unique region with world significance. It is a well-known mineralogical province, famous with collectors for its gems and minerals. Recently, the veil of secrecy has been lifted around these deposits and it is now possible for organized groups to visit them.