Formula: (Ca,Ce,La,Na)10-12(Fe,Mn)(Si,Be)20(O,OH,F)48
Origin of name: for Yevgeny Semenov, Russian mineralogist
Crystal system: orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell:
Colour: brown, reddish brown, gray
Diaphaneity: transparent to translucent
Luster: vitreous
Habit: crystals tetragonal bipyramidal, faces uneven, 0.1 to 1 mm, always in intricate mimetic (tet.) interpenetration twins
Hardness: 3.5 to 4
Specific gravity: 3.14
Cleavage: none
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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