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Sepiolite
Chemical Formula	Mg4Si6O15(OH)2·6H2O
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	2
Specific Gravity	2
Color	Grayish white, white, white with a yellowish or reddish tinge; bluish green
Streak	White
Luster	Dull, Earthy
Refractive Index	n = 1.520 n = 1.520 n = 1.530
Diaphaneity	Opaque
Crystal Habit：Compact nodular, earthy, clayey, massive; rarely fine fibrous along

Sepiolite is a clay mineral, a complex magnesium silicate, a typical formula for which is Mg₄Si₆O₁₅(OH)₂·6H₂O. It can be present in fibrous, fine-particulate, and solid forms.

It was first described in 1847 for an occurrence in Bettolino, Baldissero Canavese, Torino Province, Piedmont, Italy. The name comes from a perceived resemblance of the material to the porous bones of the cuttlefish from the Greek, "sepion". Because of its low specific gravity and its high porosity it may float upon water, hence its German name meerschaum ("sea foam").

Sepiolite occurs as a secondary mineral associated with serpentine. It can occur as a precipitate in arid environments. It may be associated with dolomite and opal.

Sepiolite is used in oil drilling and for cat litter. It is also used in a solid form for carving, where it is known as Meerschaum.

Owing to its fibrous mineral nature, sepiolite veins may contain the hazardous material, asbestos; even where asbestos is not present, sepiolite is often mistaken for it. Careful analytical techniques may be required to distinguish the two.