Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Mg$	Magnesium	element	3		constituent element	main
	$Si$	Silicon	element	4		constituent element	main
	$O$	Oxygen	element	12		constituent element	main
	$H$	Hydrogen	element	2		constituent element	main

Chemical functions

	Function	Number
	$(OH)^-$	2

Chemical bonds

	Bond	Number
	$O^--H$	1

Oxides

Formula	$MgO$	$SiO_{2}$	$H_{2}O$
Mass fraction (%)	31.88	63.37	4.75

Strunz

Class

silicates (09)

Division

phyllosilicate (09.E)

Family

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

Code

09.EC.05

Dana

Major class

silicates (VIII)

Class

phyllosilicate sheets of six-membered rings (71)

Type

with 2:1 layers (71.02)

Group

Pyrophyllite-talc group (71.02.01)

Code

71.02.01.03

Phase type

crystalline

Crystal system

monoclinic

Crystal class

prismatic

Crystal class symbol

2/m (C2h)

Crystal spacegroup

C2/c

Refringence type

biaxial

Refringence sign

negative

Birefringence

0.037 - 0.05

Refraction index $n_{\alpha}$

1.538 - 1.55

Refraction index $n_{\beta}$

1.575 - 1.594

Refraction index $n_{\gamma}$

1.575 - 1.6

Pure color

white

Color

pale green, white, gray white, yellowish white, brownish white

Diaphaneity

translucent

Luster

vitreous

Links

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