Babingtonite

Babingtonite is a calcium iron manganese inosilicate mineral with the formula Ca2(Fe,Mn)FeSi5O14(OH). It is unusual in that iron(III) completely replaces the aluminium so typical of silicate minerals. It is a very dark green to black translucent (in thin crystals or splinters) mineral crystallizing in the triclinic system with typically radial short prismatic clusters and druzy coatings. It occurs with zeolite minerals in cavities in volcanic rocks. Babingtonite contains both iron(II) and iron(III) and shows weak magnetism. It has a Mohs hardness of 5.5 to 6 and a specific gravity of 3.3.

Babingtonite
General
CategoryInosilicate
Formula
(repeating unit)		Ca2(Fe,Mn)FeSi5O14(OH)
Strunz classification9.DK.05
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Identification
ColorDark green to black
Crystal habitPrismatic crystals
CleavagePerfect on {001}, Good on {010} and {100}
FractureIrregular/uneven
TenacityBrittle
Mohs scale hardness5.5 to 6
LusterVitreous
DiaphaneityTranslucent on thin edges, opaque
Specific gravity3.3
Refractive indexnα= 1.700 nβ= 1.710 nγ= 1.725
Birefringenceδ = 0.025
PleochroismVisible
Dispersionr > v strong
References[1]

It was first described in 1824 from samples from Arendal, Aust-Agder, Norway (which is its type locality) and was named after the Irish physician and mineralogist William Babington (1757–1833).[2][3]

It is the official mineral (mineral emblem) of the Commonwealth of Massachusetts.[4] The first published report of babingtonite in Massachusetts was by Francis Alger in 1844,[5] who credited Thomas Nuttall with its discovery in Charlestown (now Somerville). The location was the Granite Street quarry, formerly known as the Milk Row quarry.[6]

  • Jet black babingtonite from Lane Quarry, Northfield, Franklin County, Massachusetts, USA
  • Triclinic crystals of babingtonite with prehnite, from Qiaojia, Qiaojia Co., Zhaotong, Yunnan, China
  • Black babingtonite which covers a matrix of botryoidal, green prehnite, and a large, colorless, doubly terminated quartz crystal
  • Babingtonite (dark) on Prehnite, Qiaojia, Qiaojia County, Yunnan Province, China

References
  1. http://www.mindat.org/min-478.html Babingtonite at Mindat.org
  2. http://webmineral.com/data/Babingtonite.shtml Webmineral
  3. http://hekint.org/william-babington/
  4. Massachusetts: Mineral or mineral emblem of commonwealth The first published report of babingtonite in Massachusetts was by Francis Alger in 1844
  5. Phillips, W., Allan, R., and Alger, F. (1844) An Elementary Treatise on Mineralogy, 5th ed. (Boston: W. D. Ticknor & Co.)
  6. Cristofono, Peter (January 19, 2019). "The Granite Street Quarry, Somerville, Massachusetts: Its History and Minerals".
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