Elbaite

Formula:   Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Origin of name:   Locality; Isle of Elba, Italy

Crystal system:   Hexagonal

Crystal class:   3m

Twinning:   Rare on {10-11} or on {40-41}

Unit cell: a = 15.86 Ǻ, c = 7.11 Ǻ

Colour:  Green, blue, red, yellow, white, colourless

Diaphaneity:

Luster:   Vitreous

Habit:   Crystals short to long prismatic, vertically striated, hemimorphic; massive, compact, columnar to fibrous

Hardness:   7

Specific gravity:   3.03 to 3.10

Cleavage:   2; {11-20} and {10-11} indistinct

Tenacity:   Conchoidal to uneven; brittle

Streak:   Colourless

Synonyms/varieties:   Achroite (colourless var.), rubellite (red var.), verdelite (green var.), tsilaisite (Mn-rich var.)

Comments:   Series with dravite; typically colour zoned