Boracite

Formula:  Mg₃B₇O₁₃Cl

Origin of name:  From borax, or composition (a borate)

Crystal system:  Orthorhombic

Crystal class:  mm2

Twinning:

Unit cell: a = 8.54 Ǻ, b = 8.54 Ǻ, c = 12.09 Ǻ

Colour:  Colourless, white, gray, yellow, pale green to dark green, bluish

Diaphaneity:

Luster:  Vitreous

Habit:  Crystals cubic, dodecahedral, tetrahedral

Hardness:  7 to 7.5

Specific gravity:  2.95

Cleavage:  None

Tenacity:  Conchoidal to uneven

Streak:

Synonyms/varieties:

Comments:  Series with ericaite