Babingtonite

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Babingtonite
8202M-babingtonite.jpg
Triclinic crystals of babingtonite with prehnite, from Qiaojia, Qiaojia Co., Zhaotong, Yunnan, China (size: 71 mm x 55 mm, 71 g)
General
Category Inosilicate
Formula
(repeating unit)
Ca2(Fe,Mn)FeSi5O14(OH)
Strunz classification 09.DK.05
Identification
Color Dark green to black
Crystal habit Prismatic crystals
Crystal system Triclinic
Cleavage Perfect on {001}, Good on {010} and {100}
Fracture Irregular/uneven
Tenacity Brittle
Mohs scale hardness 5.5 to 6
Luster Vitreous
Diaphaneity Translucent on thin edges, opaque
Specific gravity 3.3
Refractive index nα= 1.700 nβ= 1.710 nγ= 1.725
Birefringence δ = 0.025
Pleochroism Visible
Dispersion r > v strong
References [1]

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.

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]

It is the official mineral (mineral emblem) of the Commonwealth of Massachusetts.[3]

References[edit]

Babingtonite (dark) on Prehnite, Qiaojia, Qiaojia County, Yunnan Province, China . Crystal is 1.3 cm. high