| Sepiolite | |
|---|---|
 | |
| General | |
| Category | Phyllosilicates |
| Formula (repeating unit) | Mg4Si6O15(OH)2·6H2O |
| IMA symbol | Sep[1] |
| Strunz classification | 9.EE.25 |
| Dana classification | 74.03.01b.01 Palygorskite-sepiolite group |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnna |
| 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] |
| 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 | [2][3][4] |
Sepiolite,[5] also known in English by the German name meerschaum (/ˈmɪərʃɔːm/ MEER-shawm, /-ʃəm/ -shəm; German: [ˈmeːɐ̯ʃaʊm] ; meaning "sea foam"), is a soft white clay mineral, often used to make tobacco pipes (known as meerschaum pipes). A complex magnesium silicate, a typical chemical formula for which is Mg4Si6O15(OH)2·6H2O, it can be present in fibrous, fine-particulate, and solid forms.
The fibrous clay minerals have recently been shown to exist as a continuous polysomatic series where the endmembers are sepiolite and palygorskite. There is a continuous variation in chemical composition from sepiolite, the most magnesic and trioctahedral endmember, to palygorskite, the least magnesic, most Al- Fe- bearing, dioctahedral endmember.[6]
Originally named meerschaum by Abraham Gottlob Werner in 1788, it was named sepiolite by Ernst Friedrich Glocker in 1847 for an occurrence in Bettolino, Baldissero Canavese, Torino Province, Piedmont, Italy. The name comes from Greek sepion (σήπιον), meaning "cuttlebone" (the porous internal shell of the cuttlefish), + lithos (λίθος), meaning stone, after a perceived resemblance of this mineral to cuttlebone.[3] Because of its low relative density and its high porosity, it may float upon water, hence its German name. It is sometimes found floating on the Black Sea and rather suggestive of sea-foam,[7] hence the German origin of the name as well as the French name for the same substance, écume de mer.[7]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Sepiolite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 28 July 2022.
- ^ a b Sepiolite, Mindat.org, retrieved 28 July 2022
- ^ Barthelmy, David (2014). "Sepiolite Mineral Data". Webmineral.com. Retrieved 28 July 2022.
- ^ Sepiolite: mindat.org
- ^ Suárez, Mercedes; García-Romero, Emilia (2013-10-01). "Sepiolite-Palygorskite: A Continuous Polysomatic Series". Clays and Clay Minerals. 61 (5): 461–472. Bibcode:2013CCM....61..461S. doi:10.1346/CCMN.2013.0610505. ISSN 1552-8367. S2CID 101558291.
- ^ a b Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica. Vol. 18 (11th ed.). Cambridge University Press. pp. 72–73.