Ludwigite

Formula: Mg₂FeBO₅

Origin of name:  For E. Ludwig, Austrian chemist

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning: 

Unit cell: 

Colour:  Dark green, greenish black to black

Diaphaneity:  Opaque

Luster:  Silky when fibrous

Habit:  Crystals prismatic, rhombic cross section, rare; fibrous masses; embedded aggregates of acicular crystals

Hardness:  5

Specific gravity:  3.86

Cleavage:  1; {001} perfect

Tenacity: 

Streak: 

Synonyms/varieties:

Comments:  Series with vonsenite