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Spessartine

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Not to be confused with the igneous rock type spessartite, a variety of lamprophyre.
Spessartine
Spessartine crystals
General
CategoryNesosilicate
Garnet group
Formula
(repeating unit)		Mn2+3Al2(SiO4)3
IMA symbolSps[1]
Strunz classification9.AD.25
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupIa3d
Unit cella = 11.63 Å; Z = 8
Identification
ColorYellow through red
Crystal habitMassive to crystalline
CleavageNone
FractureSub-conchoidal
TenacityBrittle
Mohs scale hardness6.5 – 7.5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity4.19 calculated, 4.12 – 4.32 measured
Optical propertiesIsotropic, often anomalous double refractive
Refractive index1.800
Birefringencenone
DispersionWeak
Absorption spectraBands at 410, 420, 430 nm (or merging to form cutoff below 430 nm; also bands at 460, 480, 520 nm. Possible weak bands at 504 or 573 nm[2]
References[3][4][5]

Spessartine is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3.[2][3][4][5] This mineral is sometimes mistakenly referred to as spessartite.[6]

Spessartine's name is a derivative of Spessart in Bavaria, Germany, the type locality of the mineral.[3][4] It occurs most often in granite pegmatite[3][4][5] and allied rock types and in certain low-grade metamorphic phyllites. Sources include Australia, Myanmar, India, Afghanistan, Israel, Madagascar, Namibia, Nigeria, Mozambique, Tanzania and the United States.[2] Spessartine of an orange-yellow has been called Mandarin garnet and is found in Madagascar. Violet-red spessartines are found in rhyolites in Colorado and Maine. In Madagascar, spessartines are exploited either in their bedrock or in alluvium. The orange garnets result from sodium-rich pegmatites. Spessartines are found in bedrock in the highlands in the Sahatany valley. Those in alluvium are generally found in southern Madagascar or in the Maevatanana region.[7][8][9][10][11]

Spessartine forms a solid solution series with the garnet species almandine.[4][5] Well-formed crystals from this series, varying in color from very dark-red to bright yellow-orange, were found in Latinka, Rhodope Mountains, Kardzhali Province, Bulgaria.[12] Spessartine, like the other garnets, always occurs as a blend with other species. Gems with high spessartine content tend toward a light orange hue, while almandine prevalence induces red or brownish hues.[13]

Images

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  • Spessartine crystal from Pakistan
    Spessartine crystal from Pakistan
  • Spessartine on smoky quartz: Wushan Spessartine Mine, Tongbei, Fujian Province, China
    Spessartine on smoky quartz: Wushan Spessartine Mine, Tongbei, Fujian Province, China
  • Reddish-orange spessartine
    Reddish-orange spessartine
  • Two "frog-eyes" of 1.8 cm each sit perched atop a matrix
    Two "frog-eyes" of 1.8 cm each sit perched atop a matrix
  • Spessartine garnet on feldspar - Tongbei Yun-xiao, Fujian, China.
    Spessartine garnet on feldspar - Tongbei Yun-xiao, Fujian, China.

See also

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References

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  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. ^ a b c Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
  3. ^ a b c d Webmineral Spessartine page
  4. ^ a b c d e Mindat Spessartine page
  5. ^ a b c d "Handbook of Mineralogy Spessartine page" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2009-06-06.
  6. ^ International Mineralogical Association (1971). "International Mineralogical Association: Commission on new minerals and mineral names" (PDF). Mineralogical Magazine. 38 (293): 102–105. Bibcode:1971MinM...38..102.. doi:10.1180/minmag.1971.038.293.14.
  7. ^ "Gem News". Gems & Gemology. 34 (1): 50–63. 1998-04-01. doi:10.5741/GEMS.34.1.50.
  8. ^ Shigley, James; Dona Dirlam; Brendan Laurs; Edward Boehm; George Bosshart; William Larson (2000). "Gem localities of the 1990s". Gems & Gemology. 36 (4): 292–335. doi:10.5741/GEMS.36.4.292.
  9. ^ Laurs, Brendan; Kimberly Knox (2001). "Spessartine garnet from Ramona, San Diego County, California". Gems & Gemology. 37 (4): 278–295. doi:10.5741/GEMS.37.4.278.
  10. ^ Rossman, George R. (2009). "The geochemistry of gems and its relevance to gemology: different traces, different prices". Elements. 5 (3): 159–162. Bibcode:2009Eleme...5..159R. doi:10.2113/gselements.5.3.159. ISSN 1811-5209. S2CID 140651302.
  11. ^ Schmetzer, Karl; Thomas Hainschwang; Lore Kiefert; Heinz-Jürgen Bernhardt (2001). "Pink to pinkish orange Malaya garnets from Bekily, Madagascar". Gems & Gemology. 37 (4): 296–308. doi:10.5741/GEMS.37.4.296.
  12. ^ "Spessartine from Latinka, Bulgaria".
  13. ^ Spessartite Garnet Gemological Information
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Media related to Spessartine at Wikimedia Commons

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