Class

silicate mineral

Compound type

phyllosilicate

Comments

Montmorillonite has a typical hydration number of 10

	Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Ca$	Calcium	element	0.3	1.0	constituent element	main
	$Na$	Sodium	element	0.3	1.0	constituent element	main
	$K$	Potassium	element		1.0	constituent element	impurity
	$Al$	Aluminium	element	2	1.0	constituent element	main
	$Mg$	Magnesium	element	2	1.0	constituent element	main
	$Ti$	Titanium	element		1.0	constituent element	impurity
	$Fe^{3+}$	Iron(III) cation	element		1.0	constituent element	main
	$Si$	Silicon	element	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

Typical formula: $(Na_{0.2}Ca_{0.1})Al_2.Si_4O_{10}(OH)_2 \bullet (H_2O)_{10}$ - Common impurities: Fe, K - Too much impurities to derive a structural formula

Chemical functions

	Function	Number
	$(OH)^-$	2

Chemical bonds

	Bond	Number
	$O^--H$	1

Oxides

Formula	$Na_{2}O$	$CaO$	$Al_{2}O_{3}$	$MgO$	$SiO_{2}$	$H_{2}O$
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)

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

549.07 $g/mol$

Density

2 - 2.7 $g/cm^3$

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

white

Diaphaneity

translucent to opaque

Luster

earthy