Batisite

Formula:  (Ba,K,Na)₃Ti₂Si₄O₁₄

Origin of name:  From combination of symbols of elements

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell: a = 10.499 Å, b = 13.913 Å, c = 8.087 Å

Colour:  Dark brown

Diaphaneity: Transparent in thin splinters

Luster:  Vitreous to oily

Habit:  Elongated crystals

Hardness:  5.9

Specific gravity:  3.432

Cleavage:  1; {100} good

Tenacity: Brittle

Streak:  Rose brown

Synonyms/varieties:

Comments: Some samples are piezoelectric. Found in aegirine-arfvedsonite-microcline pegmatites in dunites