Class

silicate mineral

Compound type

phyllosilicate

Comments

Biotite phenocrysts. Content = ~5.69% (Hyperspectral cube classification maps). Some crystals are to small to be mapped with this technique.
Biotite is now a subgroup including the joins series Annite-Phlogopite, Siderophyllite-Eastonite aand Tetraferriphlogopite-Tetraferriannite

	Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Mg$	Magnesium	element	0 - 3		constituent element	main
	$Fe^{2+}$	Iron(II) cation	element	0 - 3		constituent element	main
	$Fe^{3+}$	Iron(III) cation	element	0 - 1		constituent element	main
	$Al$	Aluminium	element	0 - 3		constituent element	main
	$Si$	Silicon	element	2 - 3		constituent element	main
	$O$	Oxygen	element	12		constituent element	main
	$H$	Hydrogen	element	0 - 2		constituent element	main
	$F$	Fluorine	element	0 - 2		constituent element	main

Chemical functions

	Function	Number
	$(OH)^-$	2

Chemical bonds

	Bond	Number
	$O^--H$	1

Oxides comments

variable

Strunz

Class

silicates (09)

Division

phyllosilicate (09.E)

Family

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

Code

09.EC.20

Dana

Major class

silicates (VIII)

Class

phyllosilicate sheets of six-membered rings (71)

Type

with 2:1 layers (71.02)

Group

Mica group (Biotite subgroup) (71.02.02b)

Phase type

crystalline

Crystal system

monoclinic

Crystal class

prismatic

Crystal class symbol

2/m (C2h)

Crystal spacegroup

C2/m

Polytypes

• 1M
• 3T
• 2M1

Density

2.7 - 3.4 $g/cm^3$

Refringence type

biaxial

Refringence sign

negative

Birefringence

0.0258 - 0.066

Refraction index $n_{\alpha}$

1.530 - 1.631

Refraction index $n_{\beta}$

1.557 - 1.69

Refraction index $n_{\gamma}$

1.558 - 1.697

Dispersion V

r > v or r < v

Color

various

Diaphaneity

transparent to opaque

Luster

various