Spessartine

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Spessartine
Spessartine sur quartz fumé.jpg
Spessartine from China
General
CategoryNesosilicate
Formula
(repeating unit)
Mn2+3Al2(SiO4)3
Strunz classification09.AD.25
Crystal symmetryIsometric hexoctahedral
H-M symbol: (4/m 3 2/m)
Space group: I a3d
Unit cella = 11.63 Å; Z=8
Identification
ColorYellow through red
Crystal habitMassive to crystalline
Crystal systemIsometric
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 [1]
References[2][3][4]
 
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Spessartine
Spessartine sur quartz fumé.jpg
Spessartine from China
General
CategoryNesosilicate
Formula
(repeating unit)
Mn2+3Al2(SiO4)3
Strunz classification09.AD.25
Crystal symmetryIsometric hexoctahedral
H-M symbol: (4/m 3 2/m)
Space group: I a3d
Unit cella = 11.63 Å; Z=8
Identification
ColorYellow through red
Crystal habitMassive to crystalline
Crystal systemIsometric
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 [1]
References[2][3][4]

Spessartine or spessartite is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3.[1][2][3][4]

The name is a derivative of Spessart in Bavaria, Germany, the type locality of the mineral.[2][3] It occurs most often in granite pegmatite[2][3][4] and allied rock types and in certain low-grade metamorphic phyllites. Sources include Australia, Myanmar, India, Afghanistan, Israel, Madagascar, Tanzania and the United States.[1] 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.[5][6][7][8][9]

Spessartine forms a solid solution series with the garnet species almandine.[3][4] 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.[10]

The mineral spessartite should not be confused with a type of igneous rock, which is also called spessartite.

See also[edit]

References[edit]

  1. ^ a b c Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
  2. ^ a b c d Webmineral Spessartine page
  3. ^ a b c d e Mindat Spessartine page
  4. ^ a b c d Handbook of Mineralogy Spessartine page
  5. ^ "Gem News". Gems & Gemology 34 (1): 50–63. 1998-04-01. doi:10.5741/GEMS.34.1.50. Retrieved 2012-04-08. 
  6. ^ 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. Retrieved 2012-04-08. 
  7. ^ 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. Retrieved 2012-04-08. 
  8. ^ Rossman, George R. (2009). "The geochemistry of gems and its relevance to gemology: different traces, different prices". Elements 5 (3): 159–162. doi:10.2113/gselements.5.3.159. ISSN 1811-5209. Retrieved 2012-04-08. 
  9. ^ 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. Retrieved 2012-04-08. 
  10. ^ "Spessartine from Latinka, Bulgaria:". 
Spessartine crystal on muscovite matrix from Tanzania