Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Na$	Sodium	element	0 - 0.3		constituent element	main
	$Ca$	Calcium	element	0 - 0.15		constituent element	main
	$Mg$	Magnesium	element	0 - 3		constituent element	main
	$Fe^{2+}$	Iron(II) cation	element	0 - 1		constituent element	main
	$Al$	Aluminium	element	0 - 1.5		constituent element	main
	$Si$	Silicon	element	2.5 - 4		constituent element	main
	$O$	Oxygen	element	12 - 16		constituent element	main
	$H$	Hydrogen	element	2 - 10		constituent element	main

Composition comments

Typical formula: $(Ca_{0.1}Na_{0.1})(Mg_{2.25}Fe^{2+}_{0.75}).(Si_3Al)O_{10}(OH)_2 \bullet 4(H_2O)$ - Common impurities: Ti, Mn, Ni, K, P

Chemical functions

	Function	Number
	$(OH)^-$	2

Chemical bonds

	Bond	Number
	$O^--H$	1

Oxides

Formula	$Na_{2}O$	$CaO$	$MgO$	$FeO$	$Al_{2}O_{3}$	$SiO_{2}$	$H_{2}O$
Mass fraction (%)

Strunz

Class

silicates (09)

Division

phyllosilicate (09.E)

Family

with mica sheets, composed of tetrahedral and octahedral nets (09.EC)

Code

09.EC.45

Dana

Major class

silicates (VIII)

Class

phyllosilicate sheets of six-membered rings (71)

Type

with 2:1 clays (71.03)

Group

Smectite group (Trioctahedral Smectites) (71.03.01b)

Code

71.03.01b.02

Phase type

crystalline

Crystal system

monoclinic

Crystal class

prismatic

Crystal class symbol

2/m (C2h)

Crystal spacegroup

C2/m

Refringence type

biaxial

Refringence sign

negative

Birefringence

0.032 - 0.037

Refraction index $n_{\alpha}$

1.479 - 1.49

Refraction index $n_{\beta}$

1.51 - 1.525

Refraction index $n_{\gamma}$

1.511 - 1.527

Pure color

white

Color

white, yellowish white, greenish white, reddish white, bluish white

Diaphaneity

subtranslucent to opaque

Luster

earthy

Links

• Wikipedia
• Webmineral database
• Mindat
• Handbook of Mineralogy (Min. Soc. Am)