Sepiolite

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Sepiolite
Mineraly.sk - sepiolit.jpg
A sample of sepiolite
General
Category Phyllosilicates
Formula
(repeating unit)
Mg4Si6O15(OH)2·6H2O
Strunz classification 09.EE.25 Single tetrahedral nets of 6-membered rings
Dana classification 74.03.01b.01 Palygorskite-sepiolite group
Crystal symmetry Orthorhombic 2/m2/m2/m
Unit cell a = 5.21 Å, b = 26.73 Å, c = 13.5 Å; Z = 4
Identification
Color Grayish white, white, white with a yellowish or reddish tinge; bluish green
Crystal habit Compact nodular, earthy, clayey, massive; rarely fine fibrous along [001]
Crystal system Orthorhombic - Dipyramidal
Mohs scale hardness 2
Luster Dull, earthy
Streak White
Diaphaneity Opaque
Specific gravity 2; dry porous masses float on water
Optical properties Biaxial (-)
Refractive index nα = 1.520 nβ = 1.520 nγ = 1.530
Birefringence δ = 0.010
2V angle Measured: 20° to 70°, Calculated: 18°
References [1][2][3]

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".[2] 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.[1][3]

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.

Applications[edit]

Sepiolite is used in oil drilling, for cat litter and in a solid form for carving of items, where it is known as Meerschaum. In construction, sepiolite can be used in lime mortars as water reservoir.[4][5]

References[edit]