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Sepiolite

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Formula:
Mg4(Si6O15)(OH)2 · 6H2O
System:
Orthorhombic
Colour:
White, light gray or ...
Hardness:
2
Member of:
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.
Isostructural with:
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

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.EE.25

9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands
74.3.1b.1

74 : PHYLLOSILICATES Modulated Layers
3 : Modulated Layers with joined strips
14.4.11

14 : Silicates not Containing Aluminum
4 : Silicates of Mg
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First Recorded Occurrence of Sepiolite

Year of Discovery:
1847

Physical Properties of Sepiolite

Sub-Vitreous, Silky, Dull, Earthy
Diaphaneity (Transparency):
Translucent, Opaque
Colour:
White, light gray or light yellow.
Streak:
White
Hardness (Mohs):
2
Tenacity:
Brittle
Parting:
Good, but grain sizes are generally small and no cleavage may be seen.
Fracture:
Fibrous
Comment:
May be in parallel fibrous aggregates
Density:
2.0 - 2.2 g/cm3 (Measured)    2.25 g/cm3 (Calculated)
Comment:
May be very light due to porous aggregates

Crystallography of Sepiolite

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pnna
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 ų (Calculated from Unit Cell)
Morphology:
Needle-like fibers commonly in porous aggregates, also in fibrous sheets
Comment:
Pncn
X-Ray Powder Diffraction Data:
d-spacingIntensity
12.8 (100)
4.53 (35)
4.29 (35)
3.77 (20)
3.35 (30vb)
2.58 (45)
2.26 (16b)
Comments:
See also ICDD 13-595

Optical Data of Sepiolite

Type:
Biaxial (-)
RI values:
nα = 1.498 - 1.522 nβ = 1.507 - 1.553 nγ = 1.527 - 1.579
2V:
Measured: 20° to 70°, Calculated: 18°
Birefringence:
0.035
Max Birefringence:
δ = 0.029 - 0.057
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
none
Optical Extinction:
Z=c; parallel
Pleochroism:
Non-pleochroic
Comments:
May appear nearly isotropic. Meerschaum from Turkey reported at 1.517

Chemical Properties of Sepiolite

Formula:
Mg4(Si6O15)(OH)2 · 6H2O
Essential elements:
All elements listed in formula:
Common Impurities:
Al,Ca,Fe,Ni

Relationship of Sepiolite to other Species

Member of:
Other Members of Group:
Falcondoite(Ni,Mg)4Si6O15(OH)2 · 6H2O
Ferrisepiolite(Fe3+,Fe2+,Mg)4((Si,Fe3+)6O15)(O,OH)2 · 6H2O
LoughliniteNa2Mg3Si6O16 · 8H2O
9.EE.05BementiteMn7Si6O15(OH)8
9.EE.10BrokenhilliteMn8Si6O15(OH)10
9.EE.10Pyrosmalite-(Fe)(Fe,Mn)8Si6O15(OH,Cl)10
9.EE.10Friedelite(Mn,Fe)8Si6O15(OH,Cl)10
9.EE.10Pyrosmalite-(Mn)(Mn,Fe)8Si6O15(OH,Cl)10
9.EE.10Mcgillite(Mn,Fe)8Si6O15(OH)8Cl2
9.EE.15Nelenite(Mn,Fe)16(Si12O30)(OH)14[As33+O6(OH)3]
9.EE.15Schallerite(Mn,Fe)16Si12As3O36(OH)17
9.EE.20Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
9.EE.20TuperssuatsiaiteNa2Fe3Si8O20(OH)2 · 4H2O
9.EE.20YofortieriteMn5Si8O20(OH)2 · 8-9H2O
9.EE.20WindhoekiteCa2Fe3+2.67[Si8O20](OH)4 · 10H2O
9.EE.25Falcondoite(Ni,Mg)4Si6O15(OH)2 · 6H2O
9.EE.25LoughliniteNa2Mg3Si6O16 · 8H2O
9.EE.25Kalifersite(K,Na)5Fe73+Si20O50(OH)6 · 12H2O
9.EE.30GyroliteNaCa16Si23AlO60(OH)8 · 14H2O
9.EE.30OrlymaniteCa4Mn3Si8O20(OH)6 · 2H2O
9.EE.30TungusiteCa4Fe2Si6O15(OH)6
9.EE.35Reyerite(Na,K)2Ca14(Si,Al)24O58(OH)8 · 6H2O
9.EE.35Truscottite(Ca,Mn)14Si24O58(OH)8 · 2H2O
9.EE.40NatrosiliteNa2Si2O5
9.EE.45MakatiteNa2Si4O8(OH)2 · 4H2O
9.EE.50VarennesiteNa8Mn2Si10O25(OH,Cl)2 · 12H2O
9.EE.55RaiteNa4Mn32+Ti0.25Si8O20(OH)2 · 10H2O
9.EE.60IntersiliteNa6Mn2+Ti[Si10O24(OH)](OH)3 · 4H2O
9.EE.65Shafranovskite(Na,K)6(Mn,Fe)3Si9O24 · 6H2O
9.EE.65ZakharoviteNa4Mn5Si10O24(OH)6 · 6H2O
9.EE.70ZeophylliteCa13(Si10O28)F10 · 6H2O
9.EE.75Minehillite(K,Na)2-3Ca28Zn4Al4Si40O112(OH)16
9.EE.80Fedorite(Na,K)2-3(Ca4Na3)Si16O38(OH,F)2 · 3.5H2O
9.EE.80Martinite(Na,◻,Ca)12Ca4(Si,S,B)14B2O38(OH,Cl)2F2·4H2O
9.EE.85Lalondeite(Na,Ca)6(Ca,Na)3Si16O38(F,OH)2·3H2O
14.4.1ForsteriteMg2SiO4
14.4.2EnstatiteMgSiO3
14.4.3ClinoenstatiteMgSiO3
14.4.4ChrysotileMg3(Si2O5)(OH)4
14.4.5Clinochrysotile
14.4.6Orthochrysotile
14.4.7Parachrysotile
14.4.8LizarditeMg3(Si2O5)(OH)4
14.4.9TalcMg3(Si4O10)(OH)2
14.4.10SpadaiteMgSiO2(OH)2 · H2O (?)
14.4.12LoughliniteNa2Mg3Si6O16 · 8H2O
14.4.13EifeliteKNa3Mg4Si12O30
14.4.14Stevensite(Ca,Na)xMg3-x(Si4O10)(OH)2
14.4.15AntigoriteMg3(Si2O5)(OH)4
14.4.16 Magnesio-anthophyllite

Other Names for Sepiolite

Name in Other Languages:

Other Information

Health Risks:
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

Reference List:
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

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.
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