Andremeyerite

Formula:  BaFe₂Si₂O₇

Origin of name:  For André Marie Meyer (1890-?), Belgian mining engineer with the Geological Survey of the Belgian Congo, who first collected this mineral

Crystal system:  Monoclinic pseudo-orthorhombic

Crystal class:  2/m

Twinning: multiple on {100}

Unit cell: a = 7.488 Å, b = 13.785 Å, c = 7.085 Å, b = 118.23°

Colour:  Pale emerald-green

Diaphaneity: Transparent to translucent

Luster:

Habit:  Tiny crystals

Hardness:  5.5

Specific gravity:  4.15

Cleavage:  2; {100} and {010} perfect

Tenacity:

Streak:

Synonyms/varieties:

Comments: Found in vesicles of melilite-leucite-nephelinite; may represent crystallisation of an associated green glass.