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Spessartine

by Rick Moore last modified Oct 11, 2015 04:34 PM
A short overview of the mineral Spessartine (also known as Spessartite)

Garnets are Nesosilicates
also known as Orthosilicates


The general formula for garnets is X3Y2(SiO4)3

Spessartine, Almandine and Pyrope comprise the PyrAlSpite garnet group. This group of garnets has Al+3 (aluminum) as the Y component and one of Mn2+ (manganese), Mg2+ (magnesium), or Fe2+ (iron) as the X component.

Spessartine [Mn3Al2(SiO4)3] is the manganese-rich member of the PyrAlSpite solid solution series. The magnesium-rich member is Pyrope [Mg3Al2(SiO4)3] and and the iron-rich member is Almandine [Fe3Al2(SiO4)3].

The diagram below shows the naturally occurring compositions of garnets in the PyrAlSpite series in yellow.

PyralSpite

Image © J. H. Wittke & T. E. Bunch at the Northern Arizona Meteorite Laboratory

PyrAlSpite garnets are generally formed in high-temperature and/or high-pressure metamorphic environments like those surrounding the Adirondacks. Unlike it's relatives, Spessartine is most commonly found in granitic pegmatites and rhyolites.

Spessartine Mn3Al2(SiO4)3

 

spessatine-china

Photo by Michael A. Klimetz from the web site "Regents Earth Science and Regents Physics Web Resource".  Visit Mr. Klimetz's Spessartine Photo Gallery for more beautiful photos.

Spessartine is bright orange when pure but becomes dark orange as more Fe replaces the Mn, finally becoming red as it approaches the composition of Almandine.

Spessartine normally occurs as a "companion" species on specimens of other minerals. As such, crystals are normally small, but when they occur, they often exhibit the beautiful rhombic dodecahdron crystal form. Check out Mindat.org's interacrtive 3D model of this crystal form. You might also want to check out Webmineral's interactive 3D crystal lattice for Spessartine.

Uses: The vast majority of garnet is crushed for use as an abrasive. Some is used for sand paper, belts and discs but most ends up as the abrasive used in water jet cutting machines. A very small amount of garnet is used for faceted and polished gemstones.

Spessartine Photo Galleries Spessartine Mineral Data
Mindat.org Spessartine photo gallery Mindat.org Spessartine data
Mineral Atlas Spessartine photo gallery Mindat.org Garnet Crystal Structure
Arkenstone Spessartine Photo Gallery Webmineral Spessartine data
Alan Guisewite's Spessartine Collection
Minerals.net Spessartite(sp) data
Google Search for Spessartine images

Literature References

  • Deer,W.A., R.A.Howie, J.Zussman, 1966, An Introduction to the Rock Forming Minerals, Longman Group Ltd., London, pp. 21-31
  • Ford,W.E., 1949, Dana's Textbook of Mineralogy, 4thEd., John Wiley & Sons, London, pp, 591-597
  • Hurlbut,C.S., 1971, Dana's Manual of Mineralogy, 18thEd., John Wiley & Sons, London, pp. 377-380
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