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|System:||Orthorhombic||Colour:||White, light gray or ...|
|Name:||Named in 1847 by Ernst Friedrich Glocker from the Greek, "sepion," cuttle-fish bone, because of its low density and porous, bone like appearance. Originally named meerschaum by Abrahan Gottlieb Werner in 1788. Later translated as l'Ecume de mer. In 1794, the mineral was called keffekill by Richard Kirwan. Alexandre Brongniart called this mineral magnesite in 1807.|
Commonly found as compact masses of microscopic needles resulting in a low-density masses. May be an important constituent of "mountain leather". Free-standing acicular crystals not found in many localities.
May be confused with palygorskite. Results of García-Romero & Suárez (2010) indicate that no compositional gap exists between sepiolite and palygorskite.
Classification of Sepiolite
|IMA status:||Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"|
|Strunz 8th edition ID:||8/H.33-40|
|Nickel-Strunz 10th (pending) edition ID:||9.EE.25|
9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands
|Dana 8th edition ID:||74.3.1b.1|
74 : PHYLLOSILICATES Modulated Layers
3 : Modulated Layers with joined strips
|Hey's CIM Ref.:||14.4.11|
14 : Silicates not Containing Aluminum
4 : Silicates of Mg
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Type Occurrence of Sepiolite
|Type Locality:||Bettolino, Baldissero Canavese, Canavese District, Torino Province, Piedmont, Italy|
|Year of Discovery:||1847|
Physical Properties of Sepiolite
|Lustre:||Sub-Vitreous, Silky, Dull, Earthy|
|Diaphaneity (Transparency):||Translucent, Opaque|
|Colour:||White, light gray or light yellow.|
|Parting:||Good, but grain sizes are generally small and no cleavage may be seen.|
|Comment:||May be in parallel fibrous aggregates|
|Density (measured):||2.0 - 2.2 g/cm3|
|Density (calculated):||2.25 g/cm3|
|Comment:||May be very light due to porous aggregates|
Crystallography of Sepiolite
|Class (H-M):||mmm (2/m 2/m 2/m) - Dipyramidal|
|Cell Parameters:||a = 5.21Å, b = 26.73Å, c = 13.5Å|
|Ratio:||a:b:c = 0.195 : 1 : 0.505|
|Unit Cell Volume:||V 1,880.05 Å³ (Calculated from Unit Cell)|
|Morphology:||Needle-like fibers commonly in porous aggregates, also in fibrous sheets|
|X-Ray Powder Diffraction:|
|Comments:||See also ICDD 13-595|
Optical Data of Sepiolite
|RI values:||nα = 1.498 - 1.522 nβ = 1.507 - 1.553 nγ = 1.527 - 1.579|
|2V:||Measured: 20° to 70°, Calculated: 18°|
|Maximum Birefringence:||δ = 0.029 - 0.057|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Optical Extinction:||Z=c; parallel|
|Comments:||May appear nearly isotropic. Meerschaum from Turkey reported at 1.517|
Chemical Properties of Sepiolite
|Simplified for copy/paste:||Mg4(Si6O15)(OH)2·6H2O|
|Essential elements:||H, Mg, O, Si|
|All elements listed in formula:||H, Mg, O, Si|
Relationship of Sepiolite to other Species
|Member of:||Sepiolite Group|
|Other Members of Group:|
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Sepiolite
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Sepiolite
Glocker, E.F. (1847): Generum et specierum mineralium secundum ordines naturales digestorium synopsis. Halle, 348 pp.
Brauner, K. and A. Preisinger (1956): Struktur und Entstehung des Sepioliths. Tschermaks Mineral. Petrog. Mitt., 6, 120-140 (in German).
Brindley, G.W. (1959): X-ray and electron diffraction data for sepiolite. Amer. Mineral., 44, 495-500.
Nagata, H., S. Shimoda, and T. Sudo (1974): On dehydration of bound water of sepiolite. Clays and Clay Minerals, 22, 285-293.
Clays and Clay Minerals (1976): 43.
Guven, Necip and Carney, LeRoy L. (1979) The Hydrothermal Transformation of Sepiolite to Stevensite and the Effect of Added Chlorides and Hydroxides, Clays and Clay Minerals, 27:253-260.
García-Romero, E. & Suárez, M. (2010): On the chemical composition of sepiolite and palygorskite. Clays and Clay Minerals, 58, 1-20.
Giustetto, R., Levy, D., Wahyudi, O., Ricchiardi, G., Vitillo, J.G. (2011): Crystal structure refinement of sepiolite/indigo Maya Blue pigment using molecular modelling and synchrotron diffraction. European Journal of Mineralogy, 23, 449-466.
Internet Links for Sepiolite
Localities for Sepiolite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.