Sepiolite

Formula: Mg₄Si₆O₁₅(OH)₂.6H₂O

Origin of name: from Greek for cuttle-fish

Crystal system: orthorhombic

Crystal class: 2/m 2/m 2/m

Twinning:

Unit cell: 

Colour: whit, grayish, yellowish, may be tinted bluish green or reddish

Diaphaneity: nearly opaque

Luster: dull

Habit: massive, fine fibrous, compact nodular, earthy, clay-like

Hardness: 2 to 2.5

Specific gravity: about 2

Cleavage: none

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: when dry and porous will float on water