Bavenite

Formula:  Ca₄Be₂Al₂Si₉O₂₆(OH)₂

Origin of name:  After locality; Baveno, Piemonte, Italy

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:  On {100}

Unit cell: a = 9.71 Ǻ, b = 11.62 Ǻ, c = 4.90 Ǻ

Colour:  White, greenish white, pinkish, pale brown

Luster:  Vitreous or silky

Habit:  Crystals prismatic; fibrous or radial lamellar aggregates

Hardness:  5.5

Specific gravity:  2.71 to 2.74

Cleavage:  2; {100} perfect, {001} indistinct

Tenacity:  Brittle

Streak:  White

Synonyms/varieties:  Pilinite (Li-rich var.)

Comments: Weakly piezoelectric. Found in druses in miarolitic cavities in granites and associated pegmatites, formed by alteration of beryl and other beryllium-bearing minerals. Also found in hydrothermal veins and skarns