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.
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(n.)
A mineral occurring in triclinic crystals approaching pyroxene in angle, and of a greenish black color. It is a silicate of iron, manganese, and lime.
  

General Information:
 Chemical Formula:
Ca2(Fe++,Mn)Fe+++Si5O14(OH)
 Empirical Formula:
Ca2Fe2+0.75Mn2+0.25Fe2+(Si5O14)(OH)
 Name Origin:
Named after the Irish physicist and mineralogist, W. Babington (1757-1833).
Physical Properties:
 Cleavage:
[100] Perfect, [001] Perfect
 Color:
brownish black, greenish black, or black.
 Density:
3.4
 Diaphaniety:
Transparent to Translucent
 Habits:
Druse - Crystal growth in a cavity which results in numerous crystal tipped surfaces., Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite),
 Hardness:
5.5-6 - Knife Blade-Orthoclase
 Luminescence:
None.
 Luster:
Vitreous (Glassy)
 Streak:
brown
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