Mineral phase
- IMA name
- Montmorillonite-Beidellite-Nontronite series
- Secondary names
- Dioctahedral Smectites series
- Class
- silicate mineral
- Compound type
- phyllosilicate
- Formula
- $(Na,Ca_{0.5})_{0.3}(Al,Mg,Fe)_2.(Si,Al)_4O_{10}(OH)_2 \bullet n(H_2O)$
- Chemical formula
- [(Na)1-x(Ca)0.5(1+x)]0.3[(Al)x(Mg)y(Fe3+)1-x-y]2[(Si)x(Al)1-x]4O10(OH)2•n(H2O)
- Elemental formula
- (Na)0-0.3 (Ca)0-0.15 (Mg)0-0.35 (Fe3+)0-2 (Al)0.7-2.5 (Si)3.5-4 O12 H2
- Isotope mixture type
- terrestrial abundance
- Composition comments
- perfect solid solution - Common impurities: Ti, K
- Oxides
-
Formula $Na_{2}O$ $CaO$ $Al_{2}O_{3}$ $MgO$ $Fe_{2}O_{3}$ $SiO_{2}$ $H_{2}O$ Mass fraction (%)
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)
- End-members
- Phase type
- crystalline
- Crystal system
- monoclinic
- Crystal class
- prismatic
- Crystal class symbol
- 2/m (C2h)
- Crystal spacegroup
- C2/m
- Molar mass
- 389.27 - 549.07 $g/mol$
- Density
- 2.0 - 2.7 $g/cm^3$
- State NTP
- solid
- Refringence type
- biaxial
- Refringence sign
- negative
- Birefringence
- 0.015 - 0.035
- Refraction index $n_{\alpha}$
- 1.485 - 1.58
- Refraction index $n_{\beta}$
- 1.504 - 1.612
- Refraction index $n_{\gamma}$
- 1.505 - 1.615
- Pure color
- various
- Diaphaneity
- translucent to opaque
- Luster
- earthy