Babingtonite
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Babingtonite is a calcium iron manganese inosilicate mineral with the formula Ca₂FeSi₅O₁₄. It is unusual in that iron(III) completely replaces the aluminium so typical of silicate minerals. Wikipedia
Cleavage: Perfect on, Good on, and
Crystal class: Pinacoidal (1); (same H-M symbol)
Crystal habit: Prismatic crystals
Crystal system: Triclinic
Formula (repeating unit): Ca2(Fe,Mn)FeSi5O14(OH)
Mohs scale hardness: 5.5 to 6