Formula: (Mn, Ca)4 (Mn, Fe)9 Sb Si2 O24
Origin of name: After locality; Långban mine, Varmland, Sweden
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell:
Colour: Black
Diaphaneity: Opaque
Luster: Metallic
Habit: Crystals prismatic, complex
Hardness: 6.5
Specific gravity: 4.6 to 4.8
Cleavage: None
Tenacity:
Streak: Dark reddish brown
Synonyms/varieties:
Comments: Fe-rich variety is monoclinic, Fe-poor variety may be trigonal or pseudotrigonal
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