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Uvarovite
Uvarovite
Uvarovite
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Uvarovite
General
CategoryNesosilicate
FormulaCa3Cr2Si3O12
IMA symbolUv[1]
Strunz classification9.AD.25
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupIa3d
Unit cella = 11.99 Å; Z = 8
Identification
ColorGreen, emerald-green, green-black
Crystal habitEuhedral crystals, granular, massive
FractureUneven, conchoidal
Mohs scale hardness6.5–7.5
LusterVitreous
StreakWhite
DiaphaneityTransparent, translucent
Specific gravity3.77–3.81
Optical propertiesIsotropic
Refractive indexn = 1.865
Other characteristicsFluorescent red in both short and long UV
References[2][3][4]
Uvarovite - Saranowskiy Mine, Ural. Russia.

Uvarovite is a chromium-bearing garnet group species with the formula: Ca3Cr2(SiO4)3. It was discovered in 1832 by Germain Henri Hess who named it after Count Sergei Uvarov (1765–1855), a Russian statesman and amateur mineral collector.[2] It is classified in the ugrandite group alongside the other calcium-bearing garnets andradite and grossular.[5]

Uvarovite is the rarest of the common members of the garnet group,[6] and is the only consistently green garnet species, with an emerald-green color. It occurs as well-formed fine-sized crystals.

Occurrence

[edit]

Uvarovite most commonly occurs in solid solution with grossular or andradite, and is generally found associated with serpentinite, chromite, metamorphic limestones, and skarn ore-bodies.[6]

  • Pendant in uvarovite, a rare bright-green garnet. The long dimension is 2 cm (0.8 inch)
    Pendant in uvarovite, a rare bright-green garnet. The long dimension is 2 cm (0.8 inch)

The most significant source of uvarovite historically has been a now-closed copper mine at Outokumpu, Finland, from where most museum specimens have been collected.[7] The uvarovite crystals found in the Outokumpu district are among a wide range of chromium-rich silicate phases found in association with volcanogenic copper-cobalt-zinc sulfide ore deposits which are known to have an unusually high chromium content.[8]

Uvarovite occurrences in the United States are predominantly found in the western portion of the country, including localities in New Mexico, Arizona, and California. In the eastern United States, uvarovite has been confirmed in Lancaster County, Pennsylvania.[7] The mineral has also been reported from eastern Cuba.[9] 9 grains of uvarovite occur in a heavy mineral fraction of bulk stream sediment HM-10 collected in Bunker Hill creek, below the historic Bunker Hill gold mine, south of Nelson in British Columbia Canada. Its source is likely near serpentinites and argillaceous limestones within about 450 m upstream of the silt site.[10]

Notable localities in Europe besides the Outokumpu site known to bear uvarovite include Røros, Norway; Pitkyaranta, Russia; Val Malenco, Italy; Pico do Posets near Venasque, Spain; Kip Daglari, Turkey; and Biserk and Sarany, Russia.[7] In Africa, uvarovite has been reported from the Bushveld Igneous Complex of Transvaal, South Africa[11] and from the Vumba Schist Belt in Botswana.[12] In Asia, uvarovite has been reported from Taiwan[13] and Japan.[14] In Australia, uvarovite has been reported from chromite deposits in southern New South Wales.[15]

Properties

[edit]

Minerals in the uvarovite-grossular series are stable up to temperatures of 1410 °C at low pressure.[16]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Uvarovite

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from Grokipedia
Uvarovite is a rare, emerald-green variety of the group mineral, characterized as the calcium-chromium end-member with the Ca₃Cr₂(SiO₄)₃. It crystallizes in the isometric system, typically forming small, brilliant dodecahedral or trapezohedral crystals that are vitreous in luster and range from transparent to translucent. With a Mohs of 6.5–7.5 and a specific gravity of 3.4–3.8, uvarovite is valued for its deep green hue imparted by , though its crystals are often too small for and are instead prized as druzy specimens on matrix. This mineral occurs primarily in metamorphic environments, such as the hydrothermal alteration of -bearing or skarns in metamorphosed limestones, where it associates with minerals like , , and . Notable localities include the Saranovskii Mine in the of , the Outokumpu district in , and deposits in , , and . Its formation is linked to chromium-rich geological settings, making it one of the rarest garnets, with gem-quality material seldom exceeding 1 carat. Named in 1832 after Count Sergey Semyonovich Uvarov (1786–1855), a Russian statesman and who supported mineralogical studies, uvarovite has been collected for its aesthetic appeal since its discovery. In , it is used in jewelry as cabochons, beads, or raw druzy pieces, though its heat sensitivity requires careful handling during setting and cleaning. Despite its rarity, uvarovite holds scientific interest for understanding solid solutions and substitution in .

Etymology and History

Discovery

Uvarovite was discovered in 1832 by , a Swiss-born chemist, physician, and mineralogist who had become a prominent figure in Russian science after settling in St. Petersburg in 1830. As a professor of chemistry at the Technological Institute, Hess conducted systematic chemical analyses of mineral specimens from across the , contributing to the burgeoning field of amid the early 19th-century expansion of geological surveys in the Urals. This region, rich in metallic ores, had drawn increasing scientific attention following the mining reforms under Tsar Nicholas I, which emphasized resource exploitation and scholarly documentation of natural deposits. Hess identified the new mineral while examining chromium ore samples from the Saranovskii Mine in the southern Urals, where it occurred as vibrant emerald-green crystals embedded in serpentinized rock. Through wet chemical analysis, he determined that its intense coloration and composition set it apart from other known varieties, primarily due to significant substitution in the . This distinction prompted Hess to classify it as a novel , emphasizing its rarity and association with deposits. Hess's findings were first published later that year in the German scientific journal Annalen der Physik und Chemie, under the title "Ueber den Uwarowit, eine neue Mineralspecies," providing a concise account of its occurrence, appearance, and analytical results. This work represented a key milestone in Russian mineralogical research, bridging local explorations with European scientific discourse and establishing uvarovite's place within the group. The publication's rapid dissemination helped integrate the discovery into global mineral literature, underscoring the era's advances in applied to .

Naming and Recognition

Uvarovite derives its name from Count Sergey Semyonovich Uvarov (1786–1855), a prominent Russian statesman, classical , and amateur mineralogist who served as president of the Imperial Academy of Sciences in St. Petersburg from 1818 to 1855 and played a key role in establishing its mineral collection. The mineral was first described in 1832 by , a Russian-Swiss and mineralogist, who honored Uvarov for his contributions to Russian and his personal interest in by proposing the name "uvarovite" for this distinctive green chromium-bearing . The name originated in early Russian scientific literature following Hess's discovery in the Ural Mountains, where initial descriptions emphasized its unique emerald-green hue and chromium content, distinguishing it from other garnets known at the time. By the mid-19th century, as European mineralogists accessed Russian specimens through academic exchanges and publications, "uvarovite" gained international adoption, appearing in key texts like James Dwight Dana's System of Mineralogy (1837 edition onward), solidifying its place in global nomenclature. However, early usage sometimes led to confusion, with the term misapplied to other green garnets such as demantoid (a chromium-bearing ) or chromian , due to overlapping appearances before precise chemical analyses clarified distinctions in the late 19th century. Uvarovite's formal recognition as a valid mineral species came through the International Mineralogical Association (IMA), which classifies it as a pre-IMA approved name from 1832, grandfathered into the modern system as the chromium end-member of the garnet group with the ideal formula {Ca₃}Cr₂O₁₂. The IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) reaffirmed this status in its 2013 report on garnet supergroup nomenclature, designating uvarovite a root name within the silicate garnet subgroup without need for suffixes, based on the dominant-valency principle. This endorsement underscores its distinct identity amid the garnet family's complexity, ensuring consistent use in contemporary mineralogy.

Composition and Structure

Chemical Formula

Uvarovite has the ideal end-member Ca3Cr2(SiO4)3\mathrm{Ca_3Cr_2(SiO_4)_3}, making it a calcium-chromium within the garnet supergroup. This composition positions uvarovite as a key member of the ugrandite , alongside (Ca3Al2(SiO4)3\mathrm{Ca_3Al_2(SiO_4)_3}) and (Ca3Fe2(SiO4)3\mathrm{Ca_3Fe_2(SiO_4)_3}), where the trivalent (Cr³⁺) occupies the octahedral Y-site, substituting for aluminum (Al³⁺) or iron (Fe³⁺) found in the other end-members of this calcium-dominant series. In natural occurrences, uvarovite rarely achieves a pure end-member composition due to isomorphous substitutions, with Cr³⁺ in the Y-site commonly partially replaced by Fe³⁺ or Al³⁺, leading to empirical formulas such as Ca3(Cr,Fe,Al)2(SiO4)3\mathrm{Ca_3(Cr,Fe,Al)_2(SiO_4)_3}. Minor elements like V³⁺, Sc³⁺, or Ti⁴⁺ may also enter the Y-site, while the X-site (dodecahedral, occupied by Ca²⁺) and Z-site (tetrahedral, dominated by Si⁴⁺) show limited variability, with occasional traces of Mg²⁺, Mn²⁺, Fe²⁺, or Al³⁺. These substitutions maintain the overall of the structure, ensuring valence balance across the sites: three divalent cations at X, two trivalent (or higher-valence equivalents) at Y, three tetravalent at Z, and twelve divalent oxygen anions. The role of is central to uvarovite's identity, as Cr³⁺ specifically resides in the octahedral coordination of the Y-site, a position that distinguishes it chemically from other garnets while enabling within the ugrandite series. This site occupancy contributes to the mineral's stability under the high-pressure and temperature conditions typical of its formation, without altering the isometric .

Crystal System and Lattice

Uvarovite belongs to the isometric (cubic) crystal system and crystallizes in the Ia3d (No. 230), which defines its high symmetry and body-centered lattice arrangement. This is characteristic of the supergroup, enabling the mineral's structural stability under typical metamorphic conditions. The unit cell of uvarovite is cubic with a lattice parameter a = 11.99 Å and a volume of approximately 1723.68 ų, accommodating Z = 8 formula units per cell. These parameters reflect the close-packed arrangement of polyhedra in the garnet framework, where slight variations can arise from minor chemical substitutions, though pure end-member uvarovite maintains this idealized cubic metric. Uvarovite adopts the classic garnet structure type, consisting of a three-dimensional network of corner-sharing [SiO₄] tetrahedra (Z sites) linked to [CrO₆] octahedra (Y sites), with [CaO₈] dodecahedra (X sites) filling the interstices to form a rigid scaffold. In this configuration, calcium occupies the eight-coordinated dodecahedral sites, chromium the six-coordinated octahedral sites, and silicon the four-coordinated tetrahedral sites, contributing to the mineral's overall density and hardness. Regarding crystal habits, uvarovite predominantly occurs as drusy aggregates of well-formed dodecahedral or trapezohedral crystals, often coating host rock surfaces in compact clusters. Single, isolated crystals larger than 1 cm are exceptionally rare, and twinning is uncommon in reported specimens.

Physical and Optical Properties

Appearance and Mechanical Properties

Uvarovite displays a striking color range from vivid emerald-green to dark green-black, attributed to the presence of Cr³⁺ ions substituting for aluminum in its structure. This coloration is characteristically uniform. The mineral's luster is vitreous to subadamantine, contributing to its brilliant appearance, while its diaphaneity varies from transparent to translucent, particularly in small crystals where clarity is more pronounced. Due to the rarity of large crystals, most uvarovite occurs in drusy aggregates that may appear more opaque. Mechanically, uvarovite exhibits a Mohs of 6.5–7.5, making it suitable for use in jewelry despite its relative scarcity. Its specific gravity ranges from 3.4–3.8 g/cm³, reflecting its dense composition. The lacks cleavage, instead fracturing conchoidally, and produces a white streak when tested. These properties underscore uvarovite's durability and resistance to deformation, though its brittle nature requires careful handling in lapidary work.

Optical and Thermal Characteristics

Uvarovite, as a member of the isometric group, displays isotropic optical behavior with a of n=1.865n = 1.865. This single value arises from its cubic crystal symmetry, rendering it non-birefringent under standard conditions, though weak optical anisotropy may appear due to internal strain in some specimens. These properties make uvarovite distinguishable in gemmological testing via , where the fixed index aids in confirming its identity among green garnets. The mineral exhibits low dispersion, ranging from 0.014 to 0.021, which produces only subtle effects in transparent, gem-quality material. Additionally, uvarovite fluoresces with a strong red glow under long-wave light, a diagnostic trait activated by Cr³⁺ ions substituting in the octahedral sites. This , sometimes accompanied by greenish hues under short-wave UV, provides a key identification test in and gemmology. Thermally, pure uvarovite decomposes incongruently at approximately 1385 °C at 1 , while uvarovite-grossularite solid solutions exhibit greater thermal stability, incongruently at around 1410 ± 5 °C under low-pressure conditions. This stability reflects its robust framework, relevant for understanding its behavior in metamorphic environments and potential high-temperature applications.

Geological Occurrence

Formation Processes

Uvarovite primarily crystallizes in metamorphosed ultramafic rocks, such as and , under to conditions during regional . These environments involve the alteration of chromium-bearing ultramafic protoliths, where heat and pressure facilitate the reaction of silica, calcium, and components to form the . The process often occurs through metasomatic replacement, where fluids rich in dissolved elements infiltrate fractures and voids in the host rock, promoting . It is also associated with contact metamorphism in deposits and metasomatic zones, particularly where ultramafic intrusions interact with carbonate-rich rocks like or dolomite. Here, is sourced from chromitite layers or mafic intrusions, while calcium is mobilized from the surrounding carbonates, enabling uvarovite formation via reactions such as those between and dolomite. In paragenesis, uvarovite commonly intergrows with , , , and (chromium-bearing ), reflecting the availability of essential elements in these Cr- and Ca-enriched settings.

Major Localities

Uvarovite was first discovered at the Saranovskii Mine in the of , which serves as its type locality. This site, located in Sarany, Gornozavodskii District, , has yielded specimens of uvarovite as small, brilliant green crystals coating , typically measuring up to several millimeters across. Historical chromite mining operations here provided the primary source for early collections, though no dedicated commercial extraction of uvarovite occurs. Finland's mining district in ranks as a premier locality for uvarovite, producing some of the largest known crystals for the species, reaching up to 1-2 inches (2.5-5 cm) in exceptional cases. These vivid green, dodecahedral crystals often form drusy coatings on matrix from former and mines, such as the Mokkivaara and Keretti deposits. Like , specimens derive from historical operations rather than targeted uvarovite mining. Other significant deposits include the Jeffrey Mine in (now ), , , where uvarovite appears in association with in the remnants of a major operation. In Europe, notable occurrences are reported from , , within chromite-bearing rocks. Additional sites encompass chromite mines in (e.g., San Benito County) and (e.g., Josephine County), ; the in ; and various serpentinite outcrops in , . Globally, uvarovite remains unmined commercially, with collector specimens predominantly sourced from Russia's and Finland's region.

Uses and Significance

Gemological and Industrial Applications

Uvarovite's rarity and typically small size limit its use as a faceted , with most specimens consisting of drusy aggregates rather than individual crystals large enough for cutting into standard shapes. Despite this, it is occasionally fashioned into cabochons or shallow freeform cuts to highlight its intense emerald-green color, making it suitable for accents in high-end jewelry such as pendants, earrings, and rings. These pieces often feature the natural drusy texture for a sparkling effect, set in silver or settings to complement the stone's vibrant hue. The gem's Mohs hardness of 6.5–7.5 provides good durability for everyday wear, though its and lack of cleavage make it prone to chipping during , favoring or ornamental designs over precise cuts. Faceted uvarovite gems are exceptionally rare, seldom exceeding 1 carat, and are prized by collectors for their transparency and color intensity. Fine-quality drusy or material typically commands prices of $1–$5 per carat (as of 2025), while complete jewelry pieces like pendants range from $50–150 depending on size and setting. Industrial applications for uvarovite are negligible, as its low abundance and high value preclude large-scale extraction for uses like abrasives, where more abundant varieties or synthetic alternatives are preferred. Historically, uvarovite has seen minor ornamental use in 19th-century Russian collections, reflecting its discovery in the , but it has not been a significant material for broader jewelry production until modern techniques enabled drusy applications.

Collectibility and Research Value

Uvarovite is highly prized by mineral collectors for its vibrant emerald-green drusy crystals, which form sparkling coatings on matrix rocks, offering aesthetic appeal unmatched by other garnets. As the rarest member of the garnet group and the only consistently green variety due to its chromium content, uvarovite's scarcity drives strong demand among enthusiasts, with fine specimens from classic Russian localities commanding prices between $500 and $5,000 depending on size, crystal quality, and coverage. In scientific research, uvarovite plays a key role in understanding during metamorphic processes, particularly in zones where it records chromium mobility in ultramafic environments. It serves as an indicator for ultramafic terranes and deposits, aiding in geochemical for associated bodies through its presence in heavy mineral concentrates. Synthetic uvarovite analogs are employed in high-pressure experiments to study behavior under mantle conditions, providing insights into the elasticity and of chromium-bearing silicates via techniques like . Uvarovite holds cultural value through its prominence in major museum collections, including specimens at the featuring large, intense green crystals up to 2 cm in diameter, and at the Natural History Museum in , where it exemplifies formation. Discovered in Russia's in 1832 and named after Russian statesman Count Sergei Uvarov, it symbolizes the nation's rich mineralogical heritage without association to major artifacts. Although uvarovite faces no formal as a mineral , mining activities in its primary localities can disrupt surrounding habitats through disturbance and alteration, potentially limiting future specimen availability.

References

  1. https://www.mindat.org/min-4125.html
  2. https://galleries.com/minerals/silicate/uvarovit/uvarovit.htm
  3. https://www.gemsociety.org/article/uvarovite-garnet/
  4. https://www.britannica.com/biography/Germain-Henri-Hess
  5. http://www.minsocam.org/MSA/AmMin/Public_Access/2013_Public/Apr13_public/GrewPreprintApr_13.pdf
  6. http://webmineral.com/data/Uvarovite.shtml
  7. https://www.researchgate.net/publication/261534057_IMA_Report_Nomenclature_of_the_garnet_supergroup
  8. https://www.eas.ualberta.ca/eml/files/Garnet_nomenclature_2013_formatted.pdf
  9. https://pubs.geoscienceworld.org/books/book/chapter-pdf/3752401/9780903056434_ch04.pdf
  10. https://pdfs.semanticscholar.org/01fa/198c73f4de9a8860e043b29e0f5d1c0799ab.pdf
  11. https://pubs.geoscienceworld.org/gsw/lithosphere/article/2023/1/lithosphere_2023_214/628651/Uvarovite-from-Reduced-Native-Fe-Bearing-Paralava
  12. https://rruff.geo.arizona.edu/doclib/hom/uvarovite.pdf
  13. https://www.mdpi.com/2075-163X/9/7/395
  14. https://www.gemrockauctions.com/learn/a-z-of-gemstones/uvarovite
  15. https://geologyscience.com/gemstone/uvarovite/
  16. https://www.gemstones.com/gemopedia/uvarovite
  17. https://www.gemdat.org/gem-4125.html
  18. https://link.springer.com/article/10.1007/BF00376589
  19. http://www.handbookofmineralogy.org/pdfs/uvarovite.pdf
  20. https://pubs.geoscienceworld.org/cjmp/article-pdf/61/4/767/5936579/i2817-1713-61-4-767.pdf
  21. https://njg.geologi.no/images/NJG_articles/NGT_54_2_177-182.pdf
  22. https://pubs.geoscienceworld.org/msa/canmin/article/33/6/1263/12727
  23. https://www.mindat.org/loc-2807.html
  24. https://www.mindat.org/loc-6416.html
  25. https://www.mindat.org/locentry-560485.html
  26. https://www.gia.edu/gems-gemology/fall-2019-gemnews-uvarovite-in-prehnite
  27. https://rockchasing.com/how-much-is-garnet-worth/
  28. https://pubs.usgs.gov/fs/2006/3149/fs-2006-3149.pdf
  29. https://www.irocks.com/minerals/species/buy-uvarovite-fine-mineral-specimens-photos
  30. https://www.mdpi.com/2075-163X/10/2/94
  31. https://pubs.geoscienceworld.org/msa/ammin/article/100/2-3/588/40425/P-V-T-equation-of-state-of-Ca3Cr2Si3O12-uvarovite
  32. https://www.si.edu/object/uvarovite:nmnhmineralsciences_1149796
  33. https://www.alamy.com/uvarovite-garnet-crystals-uvarovite-is-a-mineral-comprising-calcium-chromium-silicate-it-forms-gemstones-called-garnets-that-are-characterized-by-th-image334819640.html
  34. https://www.gemselect.com/other-info/uvarovite-garnet.php
  35. https://www.mycrystals.com/meaning/uvarovite-garnet-meaning
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