Constituent
- Name
- Na-exchanged smectite SWa-1 size-fraction <1 µm
- IMA name
- Montmorillonite
- Class
- silicate mineral
- Compound type
- phyllosilicate
- Comments
- Montmorillonite has a typical hydration number of 10 - Chemical composition and molecular mass are per half unit cell
- Relevance
- main - major
- Arrangement
- homogeneous in multi-phases
- Mass fraction
- 1.0 $\pm$ 0.05
- Formula
- $Na_{0.31}(Al_{0.67}Mg_{0.07}Fe_{1.26})(Si_{3.76}Al_{0.24})O_{10}(OH)_2$
- Chemical formula
- (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2•n(H2O)
- Elemental formula
- (Na)0.31-0.3 (Al)0.91-2 (Mg)0.07-2 Fe1.26 (Si)3.76-4 O12 H2
- Isotope mixture type
- terrestrial abundance
- Composition comments
- Typical formula: $(Na_{0.2}Ca_{0.1})Al_2.Si_4O_{10}(OH)_2 \bullet (H_2O)_{10}$ - Common impurities: Fe, K - Intermolecular water was not taken into account in atomic composition calculation
- Oxides
-
Formula $SiO_{2}$ $Al_{2}O_{3}$ $MgO$ $Fe_{2}O_{3}$ $Na_{2}O$ $H_{2}O$ Mass fraction (%) 56.01 11.5 0.7 24.94 2.38 4.47
Strunz
- Class
- silicates (09)
- Division
- phyllosilicate (09.E)
- Family
- Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets (09.EC)
- Code
- 09.EC.40
Dana
- Major class
- silicates (VIII)
- Class
- phyllosilicate sheets of six-membered rings (71)
- Type
- with 2:1 clays (71.03)
- Group
- Smectite group (Dioctahedral Smectites) (71.03.01a)
- Code
- 71.03.01a.02
- Phase type
- crystalline
- Crystal system
- monoclinic
- Crystal class
- prismatic
- Crystal class symbol
- 2/m (C2h)
- Crystal spacegroup
- C2/m
- Texture
- cryptocrystalline
- Molar mass
- 403.0 $g/mol$
- Density
- N/A $g/cm^3$
- Refringence type
- biaxial
- Refringence sign
- negative
- Birefringence
- 0.015 - 0.020
- Refraction index $n_{\alpha}$
- 1.485 - 1.535
- Refraction index $n_{\beta}$
- 1.504 - 1.550
- Refraction index $n_{\gamma}$
- 1.505 - 1.550
- Dispersion V
- 0
- Color
- gray white, yellow, brownish yellow, greenish yellow
- Diaphaneity
- translucent to opaque
- Luster
- N/A