Uvarovite

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 Semenovitch 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
General
CategoryNesosilicate
Formula
(repeating unit)		Ca3Cr2Si3O12
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 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

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)

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 Roros, Norway; Pitkaranta, Finland; 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

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

See also

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Uvarovite on Mindat.org
  3. Uvarovite in the Handbook of Mineralogy
  4. Uvarovite data on Webmineral
  5. Winchell, Alexander N. (1933). "Garnet Group". Elements of Optical Mineralogy: an Introduction to Microscopic Petrography - Part II. Descriptions of Minerals (3 ed.). New York: John Wiley & Sons, Inc. p. 174. hdl:2027/uc1.b3124253.
  6. Isaacs, T. (1965). "A study of uvarovite" (PDF). Mineralogical Magazine. 35 (269): 38–45. Bibcode:1965MinM...35...38I. doi:10.1180/minmag.1965.035.269.06.
  7. Cook, Robert B. (1998). "Connoisseur's choice: uvarovite Outokumpu, Finland". Rocks & Minerals. 72 (2): 126–128. doi:10.1080/00357529809603048.
  8. Treloar, Peter J. (1987). "The Cr-minerals of Outokumpu—their chemistry and significance". Journal of Petrology. 28 (5): 867–886. doi:10.1093/petrology/28.5.867.
  9. Proenza, Joaquin; Sole, Jesus; Melgarejo, Joan Carles (1999). "Uvarovite in podiform chromite: the Moa-Baracoa ophiolitic massif, Cuba". The Canadian Mineralogist. 37: 679–690.
  10. Howard, W.R. (2016). "Surveys of recovered Visible Gold, scheelite & metallic mineral grains and Heavy Minerals in bulk stream silts 2013–2015 (Part I)" (PDF). BC MEMPR Assessment Report. #36076: 338–339.
  11. Frankel, J. J. (1959). "Uvarovite garnet and South African jade (hydrogrossular) from the Bushveld Complex, Transvaal". American Mineralogist. 44 (5–6): 565–591.
  12. Mogessie, A.; Rammlmair, D. (1994). "Occurrence of zoned uvarovite-grossular garnet in a rodingite from the Vumba Schist Belt, Botswana, Africa: implications for the origin of rodingites" (PDF). Mineralogical Magazine. 58 (392): 375–386. Bibcode:1994MinM...58..375M. doi:10.1180/minmag.1994.058.392.03. S2CID 129045367.
  13. Wan, Hsien-Ming; Yeh, Chun-Lu (1984). "Uvarovite and grossular from the Fengtien nephrite deposits, eastern Taiwan" (PDF). Mineralogical Magazine. 48 (346): 31–37. Bibcode:1984MinM...48...31W. doi:10.1180/minmag.1984.048.346.05. S2CID 140689947.
  14. Bamba, Takeo; Yagi, Kenzo; Maeda, Kenjiro (1969). "Chrome garnet from the vicinity of Nukabira Mine, Hidaka Province, Hokkaido, Japan". Proceedings of the Japan Academy. 45 (2): 109–114. doi:10.2183/pjab1945.45.109.
  15. Graham, I. T.; Franklin, B. J.; Marshall, B. (1995). "Chemistry and mineralogy of podiform chromitite deposits, southern NSW, Australia: a guide to their origin and evolution". Mineralogy and Petrology. 57 (3–4): 129–150. doi:10.1007/bf01162355. S2CID 140631372.
  16. Huckenholz, H. G.; Knittel, D. (1975). "Uvarovite: stability of uvarovite-grossularite solid solution at low pressure". Contributions to Mineralogy and Petrology. 49 (3): 211–232. Bibcode:1975CoMP...49..211H. doi:10.1007/bf00376589. S2CID 93153558.
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