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Sepiolite

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Formula:
Mg
 
4
(Si
 
6
O
 
15
)(OH)
 
2
· 6H
 
2
O
System:OrthorhombicColour:White, light gray or ...
Hardness:2
Member of:Sepiolite Group
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.
Dimorph of:Palygorskite
Isostructural with:Falcondoite, Ferrisepiolite


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.
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 (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

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:
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
Maximum Birefringence:δ = 0.029 - 0.057

Chart 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:
Mg
 
4
(Si
 
6
O
 
15
)(OH)
 
2
· 6H
 
2
O
Simplified for copy/paste:Mg4(Si6O15)(OH)2·6H2O
Essential elements:H, Mg, O, Si
All elements listed in formula:H, Mg, O, Si
Common Impurities:Al,Ca,Fe,Ni

Relationship of Sepiolite to other Species

Member of:Sepiolite Group
Other Members of Group:

- +
Falcondoite
(Ni,Mg)
 
4
Si
 
6
O
 
15
(OH)
 
2
· 6H
 
2
O
Ferrisepiolite
(Fe
3+
 
,Fe
2+
 
,Mg)
 
4
((Si,Fe
3+
 
)
 
6
O
 
15
)(O,OH)
 
2
· 6H
 
2
O
Loughlinite
Na
 
2
Mg
 
3
Si
 
6
O
 
16
· 8H
 
2
O
Related Minerals - Nickel-Strunz Grouping):

- +
9.EE.05Bementite
Mn
 
7
Si
 
6
O
 
15
(OH)
 
8
9.EE.10Brokenhillite
Mn
 
8
Si
 
6
O
 
15
(OH)
 
10
9.EE.10Pyrosmalite-(Fe)
(Fe,Mn)
 
8
Si
 
6
O
 
15
(OH,Cl)
 
10
9.EE.10Friedelite
(Mn,Fe)
 
8
Si
 
6
O
 
15
(OH,Cl)
 
10
9.EE.10Pyrosmalite-(Mn)
(Mn,Fe)
 
8
Si
 
6
O
 
15
(OH,Cl)
 
10
9.EE.10Mcgillite
(Mn,Fe)
 
8
Si
 
6
O
 
15
(OH)
 
8
Cl
 
2
9.EE.15Nelenite
(Mn,Fe)
 
16
(Si
 
12
O
 
30
)(OH)
 
14
[As
3+
3
O
 
6
(OH)
 
3
]
9.EE.15Schallerite
(Mn,Fe)
 
16
Si
 
12
As
 
3
O
 
36
(OH)
 
17
9.EE.20Palygorskite
(Mg,Al)
 
5
(Si,Al)
 
8
O
 
20
(OH)
 
2
· 8H
 
2
O
9.EE.20Tuperssuatsiaite
Na
 
2
Fe
 
3
Si
 
8
O
 
20
(OH)
 
2
· 4H
 
2
O
9.EE.20Yofortierite
Mn
 
5
Si
 
8
O
 
20
(OH)
 
2
· 8-9H
 
2
O
9.EE.20Windhoekite
Ca
 
2
Fe
3+
2.67
[Si
 
8
O
 
20
](OH)
 
4
· 10H
 
2
O
9.EE.25Falcondoite
(Ni,Mg)
 
4
Si
 
6
O
 
15
(OH)
 
2
· 6H
 
2
O
9.EE.25Loughlinite
Na
 
2
Mg
 
3
Si
 
6
O
 
16
· 8H
 
2
O
9.EE.25Kalifersite
(K,Na)
 
5
Fe
3+
7
Si
 
20
O
 
50
(OH)
 
6
· 12H
 
2
O
9.EE.30Gyrolite
NaCa
 
16
Si
 
23
AlO
 
60
(OH)
 
8
· 14H
 
2
O
9.EE.30Orlymanite
Ca
 
4
Mn
 
3
Si
 
8
O
 
20
(OH)
 
6
· 2H
 
2
O
9.EE.30Tungusite
Ca
 
4
Fe
 
2
Si
 
6
O
 
15
(OH)
 
6
9.EE.35Reyerite
(Na,K)
 
2
Ca
 
14
(Si,Al)
 
24
O
 
58
(OH)
 
8
· 6H
 
2
O
9.EE.35Truscottite
(Ca,Mn)
 
14
Si
 
24
O
 
58
(OH)
 
8
· 2H
 
2
O
9.EE.40Natrosilite
Na
 
2
Si
 
2
O
 
5
9.EE.45Makatite
Na
 
2
Si
 
4
O
 
8
(OH)
 
2
· 4H
 
2
O
9.EE.50Varennesite
Na
 
8
Mn
 
2
Si
 
10
O
 
25
(OH,Cl)
 
2
· 12H
 
2
O
9.EE.55Raite
Na
 
4
Mn
2+
3
Ti
 
0.25
Si
 
8
O
 
20
(OH)
 
2
· 10H
 
2
O
9.EE.60Intersilite
Na
 
6
Mn
2+
 
Ti[Si
 
10
O
 
24
(OH)](OH)
 
3
· 4H
 
2
O
9.EE.65Shafranovskite
(Na,K)
 
6
(Mn,Fe)
 
3
Si
 
9
O
 
24
· 6H
 
2
O
9.EE.65Zakharovite
Na
 
4
Mn
 
5
Si
 
10
O
 
24
(OH)
 
6
· 6H
 
2
O
9.EE.70Zeophyllite
Ca
 
13
(Si
 
10
O
 
28
)F
 
10
· 6H
 
2
O
9.EE.75Minehillite
(K,Na)
 
2-3
Ca
 
28
Zn
 
4
Al
 
4
Si
 
40
O
 
112
(OH)
 
16
9.EE.80Fedorite
(Na,K)
 
2-3
(Ca
 
4
Na
 
3
)Si
 
16
O
 
38
(OH,F)
 
2
· 3.5H
 
2
O
9.EE.80Martinite
(Na,◻,Ca)
 
12
Ca
 
4
(Si,S,B)
 
14
B
 
2
O
 
38
(OH,Cl)
 
2
F
 
2
·4H
 
2
O
9.EE.85Lalondeite
(Na,Ca)
 
6
(Ca,Na)
 
3
Si
 
16
O
 
38
(F,OH)
 
2
·3H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
14.4.1Forsterite
Mg
 
2
SiO
 
4
14.4.2Enstatite
MgSiO
 
3
14.4.3Clinoenstatite
MgSiO
 
3
14.4.4Chrysotile
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.5Clinochrysotile
14.4.6Orthochrysotile
14.4.7Parachrysotile
14.4.8Lizardite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.9Talc
Mg
 
3
(Si
 
4
O
 
10
)(OH)
 
2
14.4.10Spadaite
MgSiO
 
2
(OH)
 
2
· H
 
2
O (?)
14.4.12Loughlinite
Na
 
2
Mg
 
3
Si
 
6
O
 
16
· 8H
 
2
O
14.4.13Eifelite
KNa
 
3
Mg
 
4
Si
 
12
O
 
30
14.4.14Stevensite
(Ca,Na)
 
x
Mg
 
3-x
(Si
 
4
O
 
10
)(OH)
 
2
14.4.15Antigorite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
14.4.16 Magnesio-anthophyllite

Other Names for Sepiolite

Synonyms:
Parasepiolite
Other Languages:
French:Ecume de mer
L'écume de mer
German:Sepiolith
Meerschaum
Sepiolit
Russian:Сепиолит
Simplified Chinese:海泡石
Spanish:Sepiolita
Varieties:
Aluminium-sepioliteGunnbjarnite

Other Information

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

Reference List:

- +
Glocker, E.F. (1847): Generum et specierum mineralium secundum ordines naturales digestorium synopsis. Halle, 348 pp.

Brauner, K. and A. Preisinger (1956): Structur 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

Search Engines:
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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Sepiolite details from Handbook of Mineralogy (PDF)
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  • Localities for Sepiolite

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