Barylite

Formula:  BaBe₂Si₂O₇

Origin of name:  From Greek for heavy, for its high density

Crystal system:  Orthorhombic, pseudohexagonal

Crystal class:  mm2

Twinning:

Unit cell: a = 9.82 Å, b = 11.67 Å, c = 4.69 Å

Colour:  Colourless, white, bluish

Diaphaneity:  Transparent to translucent

Luster:  Vitreous

Habit:  Crystals thin tabular or prismatic; massive, disseminated grains, or veinlets

Hardness:  6 to 7

Specific gravity:  4.046

Cleavage:  2; {001} and {100} perfect, {010} imperfect

Tenacity: Brittle

Streak:

Synonyms/varieties:

Comments: May fluoresce vivid blue. Found in banded vein in a metamorphosed stratiform zinc orebody, in an "amazonite" pocket, in narrow veins in chertlike silica and albite in fenitised gneisses, in calcite veins cutting amphibole gneisses.