| Sepiolite | |
|---|---|
A sample of sepiolite |
|
| General | |
| Category | Phyllosilicates |
| Chemical formula | 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]
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.
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