Alexandrite of the Urals

History of Discovery

The history of the discovery of Ural alexandrite is unusual and extremely confused. The issue has been considered by various researchers and, in our opinion, the circumstances of the discovery and all participants in those events were most fully explained by V.B. Semenov and Karl Shmetser. It is difficult to add new facts to the above studies, so here we touch only on some of the most controversial moments in this true detective story.

vbvc

Many publications and reference books still indicate the date of alexandrite’s discovery as 1842 and the importance of the famous Finnish mineralogist Nils Gustaf Nordenskiöld in the story. The first published description of the mineral called “alexandrite” appeared in 1842 in the first volume of “Notes of the Imperial St. Petersburg Society” under Nordenskiöld’s authorship. He was not the discoverer, however, although he did visit the Urals in 1849.

According to various sources, samples of this new gem were given to him by Count Lev Alekseevich Perovsky, who was a passionate collector and lover of mineralogy and, at that time, former Gofmester of the Russian Imperial Court, Senator and head of the Department of Dependencies. Less than a year after the discovery of emerald deposits, Count Perovsky made an “inspection” trip to the area to inspect the mines, financed by the Department of Ancestors.

In 1832, such a journey was very challenging, but despite all the difficulties, he reached the emerald mines at the end of September 1832. Perovsky not only inspected the work conducted but also went to the Sretensky Mine, where he collected a large array of minerals. One, in particular, caught his attention. At first, he mistook it for a low-quality emerald. In the evening, he examined it in more detail by the flame of a candle. To his shock, this “low-quality emerald” turned a rich cherry-red color. As a great connoisseur of minerals, Perovsky immediately realized that what he had was a new, not yet known mineral. But Count Perovsky was not a professional mineralogist and researcher, and his attempts to independently study the new gem did not lead to anything. In 1833, he gave four samples of it to the Mineralogical Society in St. Petersburg. These were researched by Franz Ivanovich Werth, who first identified that the mineral was chrysoberyl.

In parallel, Perovsky sent two samples of his unknown mineral to Nordenskiöld, followed by another five samples in a letter dated 24 May 1934. Count Perovsky was so sure that he had a new mineral in front of him, that he gave it a name, even before the results of the study. At that time (April 17, 1834) all of Russia was celebrating the coming of age of Tsarevich Alexander as heir to the throne, who would be the future Emperor Alexander II. Perovsky, wanting to curry favor with the imperial family, named the unusual mineral Alexandrite. He then presented it to Tsarevich Alexander on the day of his coming of age. There is a version that Perovsky—again convinced that he had found a new mineral—sent samples to Nordenskiöld on condition that after the study, the new mineral would be officially named alexandrite. It would seem that everything is clear. Count Perovsky, during his visit to the emerald mines, found a mineral unknown to him and gave it to Werth and Nordenskiöld for research. Without waiting for the results, however, he named the gem alexandrite.

map1rgfdmap2

Geological and structural diagrams of the emerald mine area with deposits of alexandrite

 

A letter from Yakov Vasilievich Kokovin to the vice president of the cabinet of His Imperial Majesty Prince Nikolai Sergeyevich Gagarin was found in the Sverdlovsk Regional Archives in 1997. It clearly shows that Kokovin found an unknown mineral that Perovsky had already named alexandrite. The date of that letter was June 16 1834.

It follows from the letter that, as soon as Kokovin found this unknown gem, he sent it to Perovsky. Yet, this could not have happened in June 1834, because the new gem alexandrite had already been presented to Tsarevich Alexander in April 1834. But the letter was not written in June 1834, rather in June 1831, and then everything falls into place. Naturally, such an experienced explorer of the Urals and a great lover of minerals as Kokovin, who was constantly at the center of mining operations, could not help but notice the new gem. He immediately sent a report to Prince Gagarin with a sample to Count Perovsky for testing. Prince Gagarin apparently did not react to Kokovin’s report. His interests were far from mineralogy, in contrast to Perovsky, who immediately realized the uniqueness of the find and went on an “inspection” trip to the Urals.

It is clear then that Yakov Kokovin should be considered the discoverer of the Ural alexandrites, which was recognized by a number of other researchers. Why, then, was his name so quickly forgotten by both contemporaries and subsequent researchers, until 2002? Most likely this is due to the personalities of both Kokovin and Count Perovsky.

рис.3

 

Spent quarry of the Mariinsky deposit. From 1950 to 1971, the mining was open-pit to a depth of 125 meters.
Now mining is underground to 350 m

Although there is not much archival information, it seems that when Kokovin received a false denunciation for embezzlement of emeralds, it was Perovsky who initiated the audit and the case against Kokovin. Perovsky who abducted the so-called Emerald of Kokovin and blamed Kokovin for everything. Separate archival materials have survived indicating that immediately after the discovery of the emerald deposits, Perovsky tried to establish special relations with Kokovin both directly and through third parties in order to have direct access to the most unique samples.

Despite these attempts, Kokovin did not accept the proposals of Perovsky, even though they promised him considerable benefits. As a result, Perovsky could not forgive Kokovin. According to contemporaries, Count Perovsky was not only extremely energetic, persistent and persistent, but also narcissistic, ambitious, cruel and vindictive. Most likely, Perovsky did everything in his power to send a person to prison on knowingly false charges.

As a result of the “investigation” on 13 December 1835, Kokovin was removed from his post and imprisoned. He was ultimately released in 1838 but was seriously ill, and was deprived of orders, rank and noble rank. He died in 1840. Although Kokovin’s guilt was never confirmed, contemporaries tried not to mention his name. Undoubtedly, it is necessary to restore the historical truth regarding this extraordinarily talented and honest man who was the first to find alexandrite and realized that this was still a gem unknown to science.

рис. 5 1

Mining operations of “prospectors” in the dumps of the Mariinsky deposit (February 2019)

 

Brief Geological Sketch of the Emerald Mines

In the Urals, alexandrite and emerald are found in the same geological formation (micaceous), and often in the same mineral associations. Alexandrite mineralization has been discovered in half of all known emerald deposits, known in the unique ore region included in the literature under the name “Ural Emerald Mine.”

The geology of the emerald mines is widely and thoroughly covered in numerous works as well as our own. Here, then, we briefly outline only some of the structural features.

Geologically, the emerald mines region is located at the junction of the Murzinsky-Aduysky anticlinorium and the Asbest synclinorium. This boundary position led to the complexity of the tectonic structure and the spatial combination of various genetic formations.

In geological and petrographic terms, the region is divided into three zones: eastern, western and central.

The eastern zone is composed of the main and ultrabasic rocks of the Asbestian intrusion, represented by peridotites, dunites, gabbros and pyroxenites. According to the time of formation, they belong to the lower carbon.

The western zone is composed of the Permian Ageuite granite massif. Its central part is represented by small- and medium-grained biotite and two-mica granites. The central zone (also called the Ural emerald-bearing strip) is composed of the most ancient primary sedimentary rocks of the Silurian-Ordovician, metamorphosed zonally in conditions from amphibolite to green shale facies of metamorphism. In petrographic terms, the stratum is represented by carbonaceous-siliceous schists, quartzites, amphibolites and ultrabasite metamorphism products—serpentinite, talc and chlorite-talc schists. The emerald and beryllium mineralization can be traced along a strike for 25 km with a width of 0.5-1.5 km. The strike of the stratum is close to the meridional one; the dip is east at angles of 50-850.

рмс. 5 2

Samples of beryl and emerald found by “prospectors” February 2019

 

Ore bodies in deposits of the emerald mine are represented by two main types: rare-metal veins, including pegmatite and quartz-plagioclase veins; and metasomatic complexes. Among the metasomatic complexes, the following stand out: 1) graysens on granites; 2) mica complexes by ultrabasites.

Gemstones are associated mainly with mica complexes. Within the emerald mine area, 34 deposits and ore occurrences were identified, among which 20 deposits stand out, where mica complexes containing emerald, alexandrite, phenakite, beryl, chrysoberyl are present as ores. Gem material and collection samples were found in 11 deposits. The Glinskoye deposit is located 60 km from the emerald mines, and is listed here as a promising object on which alexandrite was also mined. The main deposits of alexandrite on the emerald strip are: 1. Mariinsky; 2. Sretenskoye (Sverdlovsk); 3. Cheremshanskoe; 4. Krasnobolotnoye; 5. Krasno-armeyskoye (Hitny Mine); 6. Ostrovnoye; 7. Section 616; 8. Aulskoye; 9. Shag; 10. Lublinskoe (named after Krupskaya); 11. Troitskoe (Pervomaiskoe); 12. Glinsky.

Below is brief (including historical) information on the seven main deposits of alexandrite, in which almost 100% of all its reserves and forecast resources are concentrated, as well as information on the current state of these deposits. Features of the geological structure of these deposits are not given here, since M.P. Popov well described them.

 

Mariinsky (Malyshevskoye) Mine

In the autumn of 1833, on the right bank of the Shameika River, a peasant, G.D. Karelin, found an emerald. In the spring of the following year, state-owned works were started there and the mine, Mariinsky, named after St. Mary of Egypt, expanded. In 1927, the mine was renamed in honor of the revolutionary I.M. Malyshev, and became known as the Malyshevsky deposit.

In the summer of 2019, the field was again returned to its historical name, Mariinsky. Currently, it is the only working emerald-alexandrite-beryllium deposit in Russia. Since 1834, with separate interruptions, the field has been in operation for 185 years. The deposit accounts for about 80% of all explored reserves of emeralds and more than 50% of the reserves of beryllium ores.

In 2008, the deposit once again changed ownership and was transferred to Kaliningrad Amber Plant JSC, owned by the Russian Technologies State Corporation. In 2019, the company stood out as an independent structure within the framework of the Russian Technologies Corporation, Mariinsky Prik JSC.

From 1950 to 1971, the field was mined by open-pit mining to a depth of 125 meters. To this day, it is mined by the underground method. In 2019, the depth of underground workings at the field reached 350 m from the surface. Mining operations are carried out at depths of 200 to 300 m at three horizons. Currently, exploration is at 350 m.

The Mariinsky deposit is a complex deposit; emerald, phenakite, alexandrite, and beryllium raw materials are mined here. This is the only enterprise officially supplying cut alexandrite raw materials to the market. The best samples of alexandrite are primarily purchased by the Gokhran of Russia, which is part of the Ministry of Finance. Significant dumps of the Mariinsky deposit accumulated in the vicinity of the Malyshevo settlement, which were washed and sorted at an obsolete plant. Nevertheless, the locals probably continue to sort these dumps for the tenth time, and judging by the diligence with which these works are carried out, they continue to find both emeralds and alexandrites.

рмс. 4

Significant dumps of the Mariinsky deposit accumulated in the vicinity of the Malyshevo settlement, which were washed and sorted at an obsolete plant

 

Sretenskoye (Sverdlovsk) Mine

In 1830, a peasant from the village of Beloyarki Maxim Kozhevnikov, “with his comrades,” found several fragments and crystals of a “green stone.” The commander of the Yekaterinburg lapidary factory, Yakov Kokovin, established that the crystals found were emeralds.

рис. 6 1

The current state of the Sretensky deposit, a pond in which trout is bred

Soon the Sretenskoye mine arose. Here, for the first time, Yakov Kokovin discovered phenakite and alexandrite. Later, work on the field took place with varying degrees of success. The field is now conserved, and reopened. In 1927, the Sretenskoye field was renamed Sverdlovskoye. State development of the field was carried out from 1936 to 1940 and from 1969 to 1981. At the end of 1993, Malyshevsky Emeralds OJSC began open-pit mining of the deposit. It was planned to quarry to a depth of 60 m from the surface, but this could not be done. The work was stopped at a depth of 30 m, and the quarry was flooded. Currently, the quarry is heavily forested, and trout are bred in the quarry itself. At the site of the first emeralds, a memorial sign dedicated to this event is installed.

 

Cheremshanskoye Mine 

It was discovered by the Bazhenov exploration party in the summer of 1930, when conducting geological surveys of an area of 1: 5000 scale under the direction of N.M. Uspensky. From the surface, the site is covered with a layer of loam with a thickness of 7 to 12 m, so it was not discovered in the 19th century, like the rest of the deposits. The field was developed until 1951 and was worked out to a depth of 90 m by three exploratory horizons. In total, more than 2 km of underground mine workings were completed. In 1989, the shaft of the Cheremshanskoye Mine was converted for water intake to meet the needs of enterprises in the city of Asbest.

During the mine’s operation, rock from the mine dumps was widely used for filling the railway bed, under construction at the Kvartalnoye deposit. When the railway line was almost completed, events occurred in Russia that caused the collapse of the industry and the economy. Construction of the road was stopped, as well as the work at the mines. After some time, local residents began to disassemble the canvas in order to search for emeralds and alexandrites. From time to time they found things.

Quality alexandrite raw materials sometimes appears from the Cheremshanskoye deposit, which differs from the alexandrite mined at the Mariinsky deposit. Alexandrite, like chrysoberyl, from the Mariinsky deposit shines very brightly under ultraviolet light, in contrast to the Cheremshanskoye alexandrite, which either glows very weakly or does not glow at all. It should also be noted the unusually high quality of alexandrite from this deposit.

 

Krasnobolotnoye Field

This field was opened in 1839 and worked with varying success until 1853 when it was abandoned due to the lack of emeralds. It was again developed in the late 1870s under the Poklevsky-Cosell concession. From 1915 to 1917, several hundred pounds of emerald rock were mined here, which for a long time were stored, and were washed only in 1920 to 1922. From it were extracted over 1000 crystals (“pawns”) of alexandrite, received by the Mineralogical Museum. From 1972 to 1975, limited Malyshevskaya hydraulic fracturing exploration work was conducted. A 20-m pit and a series of trenches were drilled.

рис. 9 1

The overgrown 19th-century workings of the Krasnobolotnoye field, perhaps the famous "Druze Kochubei" was found here

 

During 1993 to 2003, prospecting and assessment work was carried out on this territory, resulting in a 33-m shaft and 300 m of underground mine workings. Additional work was stopped by supervisory authorities, since a gas pipeline went through the middle of the field and funding for geological exploration ceased. At present, the entire territory of the deposit is covered with old overgrown pits and ditches.

Still, activity has not ceased. Locals clear old pits and dig new ones, sometimes revealing mica bodies, and it seems that finds of alexandrite and emerald also are occurring.

Krasnobolotnoye is probably the most famous deposit as a source of alexandrite raw material. It was here, and almost immediately after the discovery, that the alexandrite “Druza Kochubei” was found. This famous historical druzy, consisting of 22 well-formed crystals, with a very strong alexandrite effect, is currently in Russia's Mineralogical Museum of the Academy of Sciences.

рис. 9 2

The mine workings of today's "prospectors" at the Krasnobolotnoye field

 

Krasnoarmeyskoye (Chitny Priisk) Deposit

Discovered in 1838, this deposit was developed as an emerald mine with varying success until 1844.

A unique feature of this field is that there are deposits of two different genetic types. The first is emerald, found in emerald-bearing mica, and the second is tantalum-beryllium, found in rare-metal pegmatites. When mining the field for tantalum-beryllium, the depth of the mining field was exceeded, which necessitated expanding the sides of the quarry. Thus, productive micas fell into the expansion zone of the quarry. Accordingly, a rather significant amount of mica was diluted and ended up in a dump in the quarry. Nowadays, this is again the center of attraction of modern “prospectors.” In some places, they dig out the dump, and since it reaches 6-8 m in places, they place something similar to adits.

In 1972-1975, exploration work was carried out on the area of the Malyshevskoye hydraulic fracturing field, which consisted mainly of drilling pits and ditches.

рис. 11 2

"Adits," in the dump of the Krasnoarmeyskoye field, July, 2019

 

Currently, the field is owned by LLC AMI-SAYENS. In 2011, the enterprise wrote a draft and approved the project “... for conducting exploration work on emerald, alexandrite and phenakite on the western flank of the Krasnoarmeyskoye emerald-beryl deposit in 2011-2013.”

The geological task was “to identify the manifestations of emerald, alexandrite and phenakite on the western flank of the Krasnoarmeyskoye emerald-beryl deposit; ...an assessment of the resources of jewelry raw materials in category P 1 to a depth of 100 m; …selection of sites for setting assessment work based on the geological and economic assessment of identified objects…” However, for reasons unknown, exploration was never started. At present, no operations are carried out, and the quarry is flooded with water.

 

Aulskoye Field

Opened in the 19th century, this is the northern extension of the Mariinsky field. Exploration work in 1950 showed that ore mineralization is concentrated within a narrow strip of 900 x 50 m, and traced to a depth of 150 m. The deposit was mined up to 27 m. The field is currently flooded. Like the Mariinsky deposit, alexandrite was mined here along with emerald, beryl and phenakite. 

16 1

16 2

A classic crystal (1x1x0.7 cm) of alexandrite from the Cheremshanskoye deposit, exhibiting a pinacoid-bipyramidal habit. Image at the top is in daylight; above is under incandescent light.

 

Shag Deposit

A little north of the Aulskoye deposit, on the continuation of the same ore-controlling structures, is the Shag deposit. It was discovered in the 19th century, and was actively developed during the Anglo-French concession of 1899-1917. From those works, three old shaft shafts were preserved, with many overgrown pits and ditches. In 1987-1993, Malyshevskaya hydraulic fracturing prospecting work was conducted. A new 33-m mine shaft and 750 m of underground mine workings were created. Testing was carried out, which showed a high potential for emerald and alexandrite.

рис. 14

Remains of an old shaft from the time of the Anglo-French concession (1899-1917) at the Shag deposit

 

This field is not located within the emerald mine area, but much to the north (130 km from the city of Yekaterinburg, 9 km from the village of Neiva-Shaitanskoe). The history of the discovery of this field dates back to the 1970s when Neivinskaya conducted geological exploration on the area.

 

Crystallography, Mineralogy and Genetic Features of Alexandrite Mineralization 

 The first to measure and plot alexandrite crystals was Gustav Rosa (1839). From 1852 to 1862, I.N. Koksharov performed a detailed crystallographic description of alexandrite. Later, other crystals of various alexandrites were described by other authors. Of particular note is Karl Schmetser, who examined in detail the morphology of alexandrite crystals and expertly drew them.

In emerald mines, alexandrite is most often found in the form of tees, traditionally called “pawns” in the Urals, with the correct pseudo-hexagonal symmetry. The main forms are pinacoid {100}, bipyramid {111}, prism {120}, as well as {010}, {011}, {121}. The most common tees are of the pinacoid-bipyramidal habit, although tees are also quite common. Significantly less common are pinacoid habitus.

The degree of perfection of crystals can be very different, from skeletal forms to regular, well-cut, perfect crystals.

The planes of crystals are generally shiny and smooth, and only the {100} and {010} planes are covered with vertical shading. The average crystal size is 1-2 cm, rarely more. The largest of the known crystals has a size of about 9 cm in diameter (“Druze Kochubei”). The coolest of the crystals that we were able to observe and photograph had dimensions of 7x5x5 cm. Along with individual crystals, alexandrite forms drusen aggregates, the most famous of which is “Druze Kochubei,” measuring 25x16.5x11 cm, with 22 tees, and weighing 5389 grams.

 

17 1

17 2

Top: Pinacoid habit tees. The large crystal is 1.5x1.4x0.7 cm. Above: The tee of the pinacoid-bipyramidal habit and pinacoid habit. The large crystal is 2x2x1 cm. Chrysoberyl, under daylight. Private collection

In addition to well-formed crystals and their intergrowths, granular aggregates of alexandrite are found, forming thin veins, lenticular secretions and nodules with phenakite and plagioclase. Specialized work on alexandrite carried out in 2001-02 established that alexandrite-bearing veins are confined to a system of cleft cracks with a northeastern (40°-60°) strike and a steep (up to 80°) northwest fall, unlike emerald bearing bodies with a predominantly northwestern strike (290°-320°) and falling to the northeast. There is an opinion that alexandrite mineralization is confined to a localized lying side of emerald-bearing mica, that is, from the west. However, in reality, a system of cleaved cracks is formed in more rigid rocks, no matter which side they are on, from a lying or hanging side.

Due to its mineral composition, mica with alexandrite differs from emerald-bearing mica in elevated magnesium levels but lower in silicic acid. The usual paragenesis of alexandrite is emerald, phenakite, apatite, fluorite, plagioclase, topaz, margarite, and molybdenite.

18 1

18 2

Wedge-shaped twins. Top: Wedge-shaped double of alexandrite in daylight. Above: Under artificial lighting. The size of the crystal is 2.5x1.0x0.7 cm. They are generally single crystals, although rarely exist as prismatic tees

Usually, alexandrite contains a significant amount of phlogopite inclusions, which indicates the syngenetic formation of these minerals. Quite often, both alexandrite and chrysoberyl form drusen aggregates with apatite, however joint splices were not observed. In micas, as well as in quartz-plagioclase veins, it forms inclusions in fluorite, that is, earlier. In relation to phenakite, alexandrite is also earlier.

Between chrysoberyl and alexandrite, all transitional differences are observed according to the presence of the “alexandrite” effect. Very rarely, crystals were observed in which all signs of the substitution of chrysoberyl with alexandrite are observed. Part of the crystal was cleaner from inclusions and had a good “alexandrite” effect; half of the crystal retained the usual gray-green color and had a much weaker “alexandrite” effect. In combined lighting, including a UV source, some details of its internal structure are revealed. It is clearly seen that the substitution of chrysoberyl with alexandrite occurs along the faces, leaving a costal framework (skeleton) of chrysoberyl composition.

Relative to emerald, alexandrite is an earlier and higher temperature mineral. The presence of emerald and alexandrite crystals in one sample is not a frequent occurrence, but it is not an exceptional rarity either; such samples have been observed more than once.

 

20 1

20 2

Top: Skeletal tee of alexandrite in daylight. above: Under incan- descent lamp. With incoming angles on the edges between the faces of the hexagonal bipyramid and the almost degenerate faces of the pinacoid. Size is 1.5x1.5x1 cm

However, induction surfaces are usually not observed between them. It is very rare, but a direct replacement of alexandrite by emerald is noted with the formation of a peculiar pseudomorphosis of emerald by alexandrite. Also, a very successful example of substitution was recorded on the boundary of alexandrite with emerald. 

21

A classic crystal of chrysoberyl pinacoid-bipyramidal habit. The size of the central crystal is 2.5x2.2x1.0 cm, in daylight

The sample is an intergrowth of a large alexandrite crystal with smaller emerald crystals along the lower periphery of the sample. Like alexandrite and emerald in daylight, they look gray-green, however, the camera cannot fix this color, and alexandrite stains faint pink in areas. But even here, it is clearly visible how one of the alexandrite bipyramids is clearly painted in bright green. This face is in contact with an emerald crystal with a classic hexagonal crystal shape. The front of emerald formation captures one of the faces of alexandrite, which is clearly visible under incandescent light.

22 1

22 2

A fragment of a large alexandrite crystal, 7x5x5 cm. Top: In daylight; above in artificial light

 

Alexandrite Gemology

The chemical composition of alexandrite, BeAl2 О4 , also contains up to 1% Fe2 O3 and up to 0.4% Cr2 O3 , as well as impurities of some other elements such as titanium, vanadium, cobalt, nickel, manganese and copper. Basic physical properties are: hardness (8-8.5 on the Mohs scale) and a density of 3.644 to 3.763 g/cm3 . The refractive index along different crystallographic axes ranges from 1.744 to 1.758 (ng = 1.753- 1.758; nm = 1.777-1.753; np = 1.744-1.748). Birefringence (ng - np) = 0.007-0.011. The dispersion is 0.009-0.011. Pleochroism is abnormally high in three directions (trichroism). On the np axis, the color of the stone is red, red-violet; on the nm axis, it is greenish-yellow; and along the ng axis, it is green, bluish-green.

 

26 2

A fragment of a sample is alexandrite with apatite. The alexandrite crystal is pinacoid-bipyramidal, with faces of a hexagonal prism. The size of a large crystal of alexandrite is 2x1.5x1.5 cm. Apatite is 1.5x1.0x0.5 cm

A special property of alexandrite is the “alexandrite effect,” relating to its ability to change color, depending on the kind of light source. Such a color change is explained by the presence of Cr+3 in the crystal lattice, replacing Al. The “alexandrite effect” is a consequence of the strictly determined position of the bands in the absorption spectrum.

In Russia, in gemological practice, the concept of “reverse” is used, that is, the sum of the brightness values of green and red, expressed as a percentage. The reverse coefficient can vary from 10% to 90% or more. With a strong (80% to 90%) color change, a slight color tone of the original tone remains, and a weak (10% to 20%) color of a new tone appears. The Mariinsky field is subject to the Technical Conditions (TU 9645-002-26420171-94), which divide the color change into three groups: 1) with a strong effect (reverse 70% to 100%), 2) with medium effect (40% to 70%), 3) with a weak effect (10% to 40%).

Accordingly, for each of these groups, there are standards for sorting alexandrite products. The company also distinguishes three groups of clarity. The first includes transparent stones with inclusions barely visible to the naked eye. The second is transparent stones with a network of inclusions in separate areas visible to the naked eye. The third group is partially transparent stones, with inclusions in the entire volume, visible to the naked eye.

 

27 1

27 2

A splice of crystals of alexandrite with fluorite. The size of the central crystal is 1.8x1.5x1 cm. Top is in daylight. Above is under incandescent lamps

For the coloring of alexandrite, “color purity” is important, that is, lack of brownish shades. The color characteristics of alexandrite and the features of the reverse manifestation are determined both by the content of the main impurity elements, chromium and iron, and secondarily of copper, vanadium and manganese. Alexandrites of the Urals have the most intensively manifested reverse and brighter green or bluish-green color in daylight.

Alexandrite has always been highly valued. Like any gem, the price of it depends on its size, color and purity (defect-free). In the case of alexandrite, the color of the stone under various lighting conditions is also added to its purity and saturation. Ural alexandrites are rare. Both in Russia and in the international gem community, one can find various price-lists for alexandrite. However, it should be recognized that they all serve only as rough indications. In the monograph, several such price lists are given, both Russian and international. In our opinion, the “Gem Ride” data should be considered the most relevant.

 

The Future of Ural Alexandrite

What are the prospects for Ural alexandrite? What are its reserves and potential resources? Currently, there are no unequivocal answers. Moreover, estimates are completely different and often contradictory, both for the extraction of alexandrite, in general, and for the output of cut raw materials and its reserves. We do not discuss all points of view, but focus on the one that we feel is the most justified.

Since the beginning of work on emerald (and alexandrite) from 1831 to 1921, official statistics indicate that about 5 tons of alexandrite have been mined, including more than 82 kg (410,000 carats) of jewelry quality gems, which correspond to a yield of 1.6%. This value as a whole is very close to the current data of OA “Mariinsky Mine” on the extraction of cut diamonds from raw crystals. It is more difficult to estimate what the production was over the following 100 years, from 1921 to 2019. For a considerable period (1921 to 1971), there are no available data on the extraction of alexandrite. In reality, of course, the extraction of alexandrite (or simply its associated mining) did not stop during this period of time.

In the years 1921 to 1971, we estimate that about 600 kg of crystals (about 10 kg of cut material) were mined. From 1972 to 1992, our estimate is that 240 kg of crystals (4-5 kg of cut material) were mined. 

28

Inclusions of alexandrite crystals in phenakite. The size of the sample is 3x2.2.5x2.5 cm, in daylight

For the entire period 1831 to 1992, 5840 kg of crystalline raw material was extracted, including 97 kg (485,000 carats) of high-grade alexandrite. According to Laskovenkova and Zhernakova, reserves of emerald and alexandrite are 30% to 35% (i.e. one-third). Thus, alexandrite in the main deposits of 11,680 kg includes 194 kg (970,000 carats) of polished gems. This excludes the Glinskoye deposit (and the entire deposit area), which has been estimated. Alexandrite mining in 1992-2018 was not taken into account in these calculations but is considered within the margin of error. The most optimistic estimates are that 40-50 kg of crystals were extracted, giving 1.5 kg of cut gems.

Снимок

A splice of alexandrite with an emerald. Size is 4x3x3 cm. Top: Daylight in reflected light plus backlight. Above: A splice in the light of incandescent lamps, both reflected and backlight

Why, then, is only one field working even if others with li - census do not? Despite the significant potential for alexandrite, geological and economic calculations show the unprofitable operation of the emerald mine deposits in the Urals today. Objectively: for the main reserves of alexandrite (and emerald), about 80%, are located at depths of 100-500 m; all deposits of the emerald-bearing strip are characterized by very complex mining and geological conditions, both in terms of structure and water cut of deposits. This significant - ly increases the cost of exploration, mining and hence pro - duction. Still, at present, there are many proposals aimed at changing the current situation (e.g. changes in legislation and the tax burden on enterprises, the introduction of new technologies in the development of deposits, extraction of raw mate - rials, etc.)

Без имени 1

Faceted 0.8-ct alexandrite (3x2.2.5x2.5 cm). Left: In daylight. Right: Incandescent lamp. Characteristics: Reverse - 1; purity -1