Constituent Na-Montmorillonite | SSHADE

Constituent

Name: Na-Montmorillonite
IMA name: Montmorillonite-Beidellite-Nontronite series

Class: silicate mineral
Compound type: phyllosilicate

Chemical composition

Formula: $(Na_{0.07}Ca_{0.26}K_{0.005})[Al_{1.615}Fe^{3+}_{0.21}Mg_{0.28}Ti_{<0.01}][(Si_{3.945}Al_{0.055}]O_{10}(OH)_2$
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)0.07-0.3 (Ca)0.26-0.15 (Al)1.67-2.5 (Fe3+)0.21-2 (Mg)0.28-0.35 (Si)3.945-4 O12 H2
Isotope mixture type: terrestrial abundance

	Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Na$	Sodium	element	0.07 - 0.3	1.0	constituent element	main
	$Ca$	Calcium	element	0.26 - 0.15	1.0	constituent element	main
	$K$	Potassium	element	0.005	1.0	constituent element	impurity
	$Al$	Aluminium	element	1.67 - 2.5	1.0	constituent element	main
	$Fe^{3+}$	Iron(III) cation	element	0.21 - 2	1.0	constituent element	main
	$Mg$	Magnesium	element	0.28 - 0.35	1.0	constituent element	main
	$Ti$	Titanium	element	0.01	1.0	constituent element	impurity
	$Si$	Silicon	element	3.945 - 4	1.0	constituent element	main
	$O$	Oxygen	element	12	1.0	constituent element	main
	$H$	Hydrogen	element	2	1.0	constituent element	main

Composition comments: perfect solid solution - Common impurities: Ti, K - This composition is for the whole dry matter, not just the smectite fraction. From Mermut & Cano 2001. Thermal analysis DTA: endotherms at 185°C (shoulder at 235°C), desorption of water: 755°C, dehydroxylation; shoulder at 810°C, exotherms at 980°C. TG: Loss in dehydroxylation range: 5.53% (theory: 5%)

Chemical functions and bonds

Chemical functions

	Function	Number
	$(OH)^-$	2

Chemical bonds

	Bond	Number
	$O^--H$	1

Oxides composition

Oxides

Formula	$SiO_{2}$	$Na_{2}O$	$CaO$	$K_{2}O$	$Al_{2}O_{3}$	$Fe_{2}O_{3}$	$MgO$	$TiO_{2}$	$P_{2}O_{5}$
Mass fraction (%)	61.46	1.47	1.18	0.2	22.05	4.37	2.94	0.09	0.003

Oxides comments

From Mermut & Cano 2001. Loss on heating: -550°C: 0.61-1.59%; 550-1000°C: 4.47-5.15%

Classifications

Strunz

Class: silicates (09)
Division: phyllosilicate (09.E)
Family: 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)

Phase type: crystalline

Crystallography

Crystal system: monoclinic
Crystal class: prismatic
Crystal class symbol: 2/m (C2h)
Crystal spacegroup: C2/m

Texture: cryptocrystalline

Physical properties

Molar mass: 389.27 - 549.07 $g/mol$
Density: 2.0 - 2.7 $g/cm^3$

Optical properties

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
Color: gray-green
Diaphaneity: translucent to opaque
Luster: earthy