Class

silicate mineral

Compound type

phyllosilicate

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

Phyllosilicates 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

Texture

monocrystalline

Molar mass

379.27 $g/mol$

Density

2.7 - 2.8 $g/cm^3$

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

Color

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

Diaphaneity

translucent

Luster

vitreous