Physical Properties
Chemical formula KAl2(AlSi3O10)(OH)2
Class Phyllosilicate
Sheets of linked tetrahedra
Crystal system Monoclinic
Habit Disseminated grains
Books with or without
pseudohexagonal outline
Color White, gray-brown
Hardness 2 to 2.5
Specific gravity 2.8
Cleavage Perfect basal (001)
Fracture Elastic
Luster Vitreous
Transparency Translucent
Streak White
Optical Properties
PPL Colorless
Basal cleavage may be visible as parallel lines
XPL Birdseye extinction
High 2nd order,  low 3rd order colors
δ 0.035
Extinction Birdseye
after Perkins, 322

Muscovite in Hand Sample

Muscovite in garnet muscovite schist
Muscovite in magnetite muscovite schist
Muscovite in muscovite staurolite schist
Muscovite with biotite and garnet in Maidens gneiss
Muscovite in muscovite hornblende schist
Scanning electron micrograph of muscovite (Note: it always does that. Every single time. Everything looks great until the image finishes stitching, and then WHAM! Great big black holes. The important thing here is that the black holes aren’t totally obscuring the micaceous cleavage.)

Muscovite in Thin Section

Thin Section GigaPans

Muscovite, plane polars
Muscovite, crossed polars
Fine-grained muscovite with chlorite (green), plane polars
Fine-grained muscovite with chlorite, crossed polars
Muscovite with biotite and garnet in Maidens gneiss, plane polars
Muscovite with biotite and garnet in Maidens gneiss, crossed polars

Muscovite, PPL

Muscovite, XPL

Fine-grained muscovite with chlorite (green), PPL

Fine-grained muscovite with chlorite, XPL

The following two pictures and videos are of an anhedral garnet in the Maidens Gneiss. A number of muscovite grains are also visible.

Anhedral garnet with adjacent muscovite, PPL

Anhedral garnet with adjacent muscovite, XPL

Further Reading

Muscovite at
Muscovite at