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Montmorillonite

Formula:
(Na,Ca)
 
0.33
(Al,Mg)
 
2
Si
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
System:MonoclinicColour:White, pale pink, buff, ...
Hardness:1 - 2
Name:For the type locality at Montmorillon, Vienne, Poitou-Charentes, France.


Montmorillonite-Vermiculite Group.

A clay mineral.

Classification of Montmorillonite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/H.19-20
Nickel-Strunz 10th (pending) edition ID:9.EC.40

9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
Dana 8th edition ID:71.3.1a.2

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
3 : Sheets of 6-membered rings with 2:1 clays
Hey's CIM Ref.:16.7.9

16 : Silicates Containing Aluminum and other Metals
7 : Aluminosilicates of Mg
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Type Occurrence of Montmorillonite

Type Locality:Montmorillon, Vienne, Poitou-Charentes, France
Year of Discovery:1847

Occurrences of Montmorillonite

Geological Setting:Alteration product of volcanic tuffs and ash.

Physical Properties of Montmorillonite

Lustre:Dull, Earthy
Diaphaneity (Transparency):Translucent
Colour:White, pale pink, buff, yellow, red, green
Hardness (Mohs):1 - 2
Cleavage:Perfect
on {001}
Fracture:Irregular/Uneven
Density (measured):2 - 3 g/cm3

Crystallography of Montmorillonite

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:B2/m (B1 1 2/m) [C2/m] {C1 2/m 1}
Cell Parameters:a = 5.17Å, b = 8.94Å, c = 9.95Å
β = 99.54°
Ratio:a:b:c = 0.578 : 1 : 1.113
Unit Cell Volume:V 453.53 ų (Calculated from Unit Cell)
Z:1
Morphology:Scaly crystals, clayey, compact, massive

Optical Data of Montmorillonite

Type:Biaxial (-)
RI values: nα = 1.485 - 1.535 nβ = 1.504 - 1.550 nγ = 1.505 - 1.550
2V:Measured: 5° to 30°
Maximum Birefringence:δ = 0.020

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Low
Dispersion:none
Pleochroism:Visible
Comments:X= colorless to pale brown, yellow green
Y= dark brown to yellow-green, olive-green, pale yellow
Z= brown to olive-green, pale yellow

Chemical Properties of Montmorillonite

Formula:
(Na,Ca)
 
0.33
(Al,Mg)
 
2
Si
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
Essential elements:Al, H, Na, O, Si
All elements listed in formula:Al, Ca, H, Mg, Na, O, Si
Common Impurities:Fe,K

Relationship of Montmorillonite to other Species

Member of:Smectite Group
Related Minerals - Nickel-Strunz Grouping):
9.EC.05Minnesotaite
(Fe,Mg)
 
3
Si
 
4
O
 
10
(OH)
 
2
9.EC.05Talc
Mg
 
3
Si
 
4
O
 
10
(OH)
 
2
9.EC.05Willemseite
(Ni,Mg)
 
3
Si
 
4
O
 
10
(OH)
 
2
9.EC.10Ferripyrophyllite
Fe
 
2
Si
 
4
O
 
10
(OH)
 
2
9.EC.10Pyrophyllite
Al
 
2
Si
 
4
O
 
10
(OH)
 
2
9.EC.15Boromuscovite
KAl
 
2
[(OH)
 
2
|BSi
 
3
O
 
10
]
9.EC.15Celadonite
K(Mg,Fe
2+
 
)(Fe
3+
 
,Al)[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.15Chernykhite
(Ba,Na)(V
3+
 
,Al,Mg)
 
2
[(OH)
 
2
|(Si,Al)
 
4
O
 
10
]
9.EC.15Montdorite
(K,Na)
 
2
(Fe
2+
 
,Mn
2+
 
,Mg)
 
5
[(OH,F)
 
2
|Si
 
4
O
 
10
]
 
2
9.EC.15Muscovite
KAl
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Nanpingite
CsAl
 
2
[(OH,F)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Paragonite
NaAl
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Roscoelite
K(V,Al)
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Tobelite
(NH
 
4
,K)Al
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Aluminoceladonite
K(Mg,Fe
2+
 
)(Al,Fe
3+
 
)[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.15Chromphyllite
K(Cr,Al)
 
2
[(OH,F)
 
2
|AlSi
 
3
O
 
10
]
9.EC.15Ferro-aluminoceladonite
K(Fe
2+
 
,Mg)(Al,Fe
3+
 
)[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.15Ferroceladonite
K(Fe
2+
 
,Mg)(Fe
3+
 
,Al)[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.15Chromceladonite
K(Mg,Fe
2+
 
)(Cr,Al)[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.15Tainiolite
KLiMg
 
2
[F
 
2
|Si
 
4
O
 
10
]
9.EC.15Ganterite
(Ba,Na,K)(Al,Mg)
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Annite
KFe
2+
3
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Biotite
9.EC.20Ephesite
NaLiAl
 
2
[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.20Hendricksite
K(Zn,Mg,Mn
2+
 
)
 
3
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Masutomilite
(K,Rb)(Li,Mn
3+
 
,Al)
 
3
[(F,OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Norrishite
KLiMn
2+
2
[(OH)
 
2
|Si
 
4
O
 
10
]
9.EC.20Phlogopite
KMg
 
3
[(OH,F)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Polylithionite
KLi
 
2
Al[(F,OH)
 
2
|Si
 
4
O
 
10
]
9.EC.20Preiswerkite
NaMg
 
2
Al[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.20Siderophyllite
KFe
2+
2
Al[(F,OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.20Tetra-ferriphlogopite
KMg
 
3
[(OH,F)
 
2
|(Fe
3+
 
,Al)Si
 
3
O
 
10
]
9.EC.20Wonesite
(Na,K)(Mg,fe,Al)
 
6
(Al,Si)
 
8
O
 
20
(OH,F)
 
4
9.EC.20Zinnwaldite
KLiFe
2+
 
Al[(F,OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Eastonite
KMg
 
2
Al[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.20Tetraferriannite
KFe
2+
3
[(OH)
 
2
|(Fe
3+
 
,Al)Si
 
3
O
 
10
]
9.EC.20Trilithionite
K(Li,Al)
 
3
[(F,OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Fluorannite
KFe
2+
3
[(F,OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Shirokshinite
KNaMg
 
2
[F
 
2
|Si
 
4
O
 
10
]
9.EC.20Shirozulite
K(Mn
2+
 
,Mg)
 
3
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Sokolovaite
CsLi
 
2
AlSi
 
4
O
 
10
F
 
2
9.EC.20Aspidolite
NaMg
 
3
[(OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.20Fluorophlogopite
KMg
 
3
[(F,OH)
 
2
|AlSi
 
3
O
 
10
]
9.EC.25Brammallite
Na
 
0.65
Al
 
2.0
ٱAl
 
0.65
Si
 
3.35
O
 
10
(OH)
 
2
9.EC.30Margarite
CaAl
 
2
[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.35Anandite
(Ba,K)(Fe
2+
 
,Mg)
 
3
[(O,OH)
 
2
|(Si,Al,Fe)
 
4
O
 
10
]
9.EC.35Bityite
CaLiAl
 
2
[(OH)
 
2
|BeAlSi
 
2
O
 
10
]
9.EC.35Clintonite
Ca(Mg,Al)
 
3
[(OH)
 
2
|Al
 
3
SiO
 
10
]
9.EC.35Kinoshitalite
(Ba,K)(Mg,Mn
2+
 
,Al)
 
3
[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.35Ferrokinoshitalite
(Ba,K)(Fe
2+
 
,Mg)
 
3
[(OH,F)
 
2
|Al
 
2
Si
 
2
O
 
10
]
9.EC.35Oxykinoshitalite
(Ba,K)(Mg,Ti,Fe
3+
 
,Fe
2+
 
)
 
3
[(O,OH,F)
 
2
|(Si,Al)
 
4
O
 
10
]
9.EC.40Beidellite
(Na,Ca
 
0.5
)
 
0.3
Al
 
2
(Si,Al)
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
9.EC.40Kurumsakite
(Zn,Ni,Cu)
 
8
Al
 
8
V
 
2
Si
 
5
O
 
35
·27H
 
2
O (or near)
9.EC.40Nontronite
Na
 
0.3
Fe
 
2
(Si,Al)
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
9.EC.40Volkonskoite
Ca
 
0.3
(Cr,Mg,Fe)
 
2
(Si,Al)
 
4
O
 
10
(OH)
 
2
·4H
 
2
O
9.EC.40Yakhontovite
(Ca,Na)
 
0.5
(Cu,Fe,Mg)
 
2
Si
 
4
O
 
10
(OH)
 
2
·3H
 
2
O
9.EC.40Smectite
9.EC.45Hectorite
Na
 
0.3
(Mg,Li)
 
3
Si
 
4
O
 
10
(F,OH)
 
2
9.EC.45Saponite
Ca
 
0.25
(Mg,Fe)
 
3
(Si,Al)
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
9.EC.45Sauconite
Na
 
0.3
Zn
 
3
(Si,Al)
 
4
O
 
10
(OH)
 
2
·4H
 
2
O
9.EC.45Spadaite
MgSiO
 
2
(OH)
 
2
·H
 
2
O
9.EC.45Stevensite
(Ca,Na)
 
x
Mg
 
3
Si
 
4
O
 
10
(OH)
 
2
9.EC.45Swinefordite
Li(Al,Li,Mg)
 
4
(Si,Al)
 
8
O
 
20
,(OH,F)
 
4
·xH
 
2
O
9.EC.45Zincsilite
Zn
 
3
Si
 
4
O
 
10
(OH)
 
2
·4H
 
2
O
9.EC.45Ferrosaponite
Ca
 
0.3
(Fe
2+
 
,Mg,Fe
3+
 
)
 
3
(Si,Al)
 
4
O
 
10
(OH)
 
2
·4H
 
2
O
9.EC.50Vermiculite
(Mg,Fe,Al)
 
3
(Al,Si)
 
4
O
 
10
(OH)
 
2
·4H
 
2
O
9.EC.55Baileychlore
(Zn,Fe,Al,Mg)
 
6
(Si,Al)
 
4
O
 
10
(OH)
 
8
9.EC.55Chamosite
(Fe
2+
 
,Mg)
 
5
Al[(OH)
 
8
|AlSi
 
3
O
 
10
]
9.EC.55Clinochlore
(Mg,Fe
2+
 
)
 
5
Al[(OH)
 
8
|AlSi
 
3
O
 
10
]
9.EC.55Cookeite
LiAl
 
4
(Si
 
3
Al)O
 
10
(OH)
 
8
9.EC.55Franklinfurnaceite
Ca
 
2
FeMn
 
3
MnZn
 
2
Si
 
2
O
 
10
(OH)
 
8
9.EC.55Gonyerite
(Mn,Mg)
 
5
Fe(Si
 
3
Fe)O
 
10
(OH)
 
8
9.EC.55Nimite
(Ni,Mg,Al)
 
6
(Si,Al)
 
4
O
 
10
(OH)
 
8
9.EC.55Orthochamosite
(Fe,Mg,Fe)
 
5
Al(Si
 
3
Al)O
 
10
(OH,O)
 
8
9.EC.55Pennantite
(Mn
 
5
Al)(Si
 
3
Al)O
 
10
(OH)
 
8
9.EC.55Sudoite
(Mg,Fe
2+
 
)
 
2
Al
 
3
[(OH)
 
8
|AlSi
 
3
O
 
10
]
9.EC.55Donbassite
Al
 
2
[Al
 
2.33
][Si
 
3
AlO
 
10
](OH)
 
8
9.EC.55Glagolevite
Na(Mg,Al)
 
6
[(OH,O)
 
8
|AlSi
 
3
O
 
10
]
9.EC.55Borocookeite
Li
 
1+3x
Al
 
4-x
[(BSi
 
3
)O
 
10
](OH)
 
8
[0.00 <= x <=0.33]
9.EC.60Aliettite
Ca
 
0.2
Mg
 
6
(Si,Al)
 
8
O
 
20
(OH)
 
4
·4H
 
2
O
9.EC.60Corrensite
(Mg,Fe)
 
9
(Si,Al)
 
8
O
 
20
(OH)
 
10
·nH
 
2
O
9.EC.60Dozyite
Mg
 
7
Al
 
2
[(OH)
 
12
|Al
 
2
Si
 
4
O
 
15
]
9.EC.60Hydrobiotite
9.EC.60Karpinskite
(Ni,Mg)
 
2
Si
 
2
O
 
5
(OH)
 
2
9.EC.60Kulkeite
Mg
 
8
Al(AlSi
 
7
)O
 
20
(OH)
 
10
9.EC.60Lunijianlaite
Li
 
0.7
Al
 
6.2
(Si
 
7
AlO
 
20
)(OH,O)
 
10
9.EC.60Rectorite
(Na,Ca)Al
 
4
(Si,Al)
 
8
O
 
20
(OH)
 
4
·2H
 
2
O
9.EC.60Saliotite
Li
 
0.5
Na
 
0.5
Al
 
3
Si
 
3
AlO
 
10
(OH)
 
5
9.EC.60Tosudite
9.EC.60Brinrobertsite
Na
 
0.3
Al
 
4
[(OH)
 
2
|Si
 
4
O
 
10
]
 
2
· 3.5 H
 
2
O
9.EC.65Macaulayite
(Fe,Al)
 
24
Si
 
4
O
 
43
(OH)
 
2
9.EC.70Burckhardtite
Pb
 
2
(Fe,Mn)AlTeO
 
2
Si
 
3
O
 
10
(OH)
 
2
·H
 
2
O
9.EC.75Ferrisurite
(Pb,Ca)
 
2-3
(CO
 
3
)
 
1.5-2
(OH,F)
 
0.5-1
[(Fe,Al)
 
2
Si
 
4
O
 
10
(OH)
 
2
]·nH
 
2
O
9.EC.75Surite
Pb(Pb,Ca)(CO
 
3
)
 
2
(Al,Fe,Mg)
 
2
(Si,Al)
 
4
O
 
10
(OH)
 
2
9.EC.75Niksergievite
(Ba,Ca)
 
2
(Al,Si)
 
7
O
 
10
(CO
 
3
)(OH)
 
6
·nH
 
2
O
9.EC.80Kegelite
Pb
 
12
(Zn,Fe)
 
2
Al
 
4
(SO
 
4
)
 
4
Si
 
11
O
 
38
or near
Related Minerals - Hey's Index Grouping:
16.7.1Pyrope
Mg
 
3
Al
 
2
[SiO
 
4
]
 
3
16.7.2Sapphirine
(Mg,Fe)
 
4-x
Al
 
4+x
[Al
 
4+x
Si
 
2-x
O
 
18
]O
 
2
16.7.3Sapphirine-1A
(Mg,Al,Fe
2+
 
)
 
8
[(Al,Si,Fe
3+
 
)
 
6
O
 
18
]O
 
2
16.7.4Magnesiochloritoid
MgAl
 
2
[O|(OH)
 
2
|SiO
 
4
]
16.7.5Kulkeite
Mg
 
8
Al(AlSi
 
7
)O
 
20
(OH)
 
10
16.7.6Palygorskite
(Mg,Al)
 
5
(Si,Al)
 
8
O
 
20
(OH)
 
2
·8H
 
2
O
16.7.7Saponite
Ca
 
0.25
(Mg,Fe)
 
3
(Si,Al)
 
4
O
 
10
(OH)
 
2
·nH
 
2
O
16.7.8Aliettite
Ca
 
0.2
Mg
 
6
(Si,Al)
 
8
O
 
20
(OH)
 
4
·4H
 
2
O
16.7.10Baumite
(Mg,Al,Mn,Zn,Fe)
 
3
(Si,Al)
 
2
O
 
5
(OH)
 
4

Other Names for Montmorillonite

Synonyms:
AmagorsiteDaunialiteFuller's EarthGoumbrineGumbrine
StolpeniteWalkerite (of Dana)Walkthon
Esperanto names:
Montmorijonito
German names:
FullererdeGiliabitMontmorillonitStolpenit
Spanish names:
MontmorillonitaStolpenita
Varieties:
AlumodeweyliteAskaniteCalcium-MontmorilloniteDelanovite

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 Montmorillonite

Reference List:Grim, Ralph Early & G. Kulbicki (1961), Montmorillonite: high-temperature reactions and classification: American Mineralogist: 46: 1329-1369.

Tettenhorst, R. and W.D. Johns (1966), Interstratification in montmorillonite: Clays and Clay Minerals: 25: 85-93.

McAtee, J.L. & W. Henslee (1969), Electron microscopy of montmorillonite dispersed at various pH: American Mineralogist: 54: 869-874.

Shutov, V.D., V.A. Drits, and B.A. Sakharov (1969a), On the mechanism of a postsedimentary transformation of montmorillonite into hydromica. In L. Heller, Ed., Proceedings International Clay Conference, Tokyo, 1969, 1: 523-532, Jerusalem University.

Shutov, V.D., V.A. Drits, and B.A. Sakharov (1969b), On the mechanism of a postsedimentary transformation of montmorillonite into hydromica: Discussion. In L. Heller, Ed., Proceedings International Clay Conference, Tokyo, 1969, 2: 126-129, Jerusalem University.

Tettenhorst, R. and Roberson, H.E. (1973) X-ray diffraction aspects of montmorillonite. American Mineralogist: 58: 73-80.

Gillespie, J. B., J.D. Lindberg & M.S. Smith (1974), Visible and near-infrared absorption coefficients of montmorillonite and related clays: American Mineralogist: 59: 1113-1116.

Lagaly, G., M. Fernandez-Gonzalez, and A. Weiss (1976), Problems in layer-charge determination of montmorillonites: Clay Minerals: 11: 173-187.

Sherman, D.M. and N. Vergo (1988), Optical spectrum, site occupancy, and oxidation state of Mn in montmorillonite: American Mineralogist: 73: 140-144.

American Mineralogist (1989): 74: 627.

Muller, F., G. Besson, A. Manceau, and V.A. Drits (1997), Distribution of isomorphous cations within octahedral sheets in montmorillonite from Camp-Bertaux: Physica and Chemistry of Minerals: 24: 159-166.

Christidis, George E. (2006), Genesis and compositional heterogeneity of smectites. Part III: Alteration of basic pyroclastic rocks - A case study from the Troodos Ophiolite Complex, Cyprus: American Mineralogist: 91: 685-701.

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    Localities for Montmorillonite

    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.
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    Mineral and/or Locality
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