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
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, Plane Polars
Muscovite in plane polarized light. Magnification: 40x To view this mineral in XPL, click here: https://youtu.be/O4kDGJG551Y To explore this slide in plane p…
Muscovite, Crossed Polars
Muscovite displaying its characteristic moderate birefringence and birdseye extinction. Magnification: 40x To view this mineral in PPL, click here: https://y…
Muscovite and Chlorite, Plane Polars
Muscovite interspersed with chlorite (the brownish green pleochroic mineral) in plane polarized light. Magnification: 100x Rock: garnet mica schist To view t…
Muscovite and Chlorite, Crossed Polars
Muscovite displaying its characteristic moderate birefringence and birdseye extinction in cross-polarized light. Magnification: 100x Rock: garnet mica schist…
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, Plane Polars
Anhedral garnet in the Maidens Gneiss from the Goochland Terrane in central Virginia. Magnification: 40x Rock: Maidens Gneiss To view this mineral in crossed…
Anhedral Garnet, Crossed Polars
Anhedral garnet in the Maidens Gneiss from the Goochland Terrane in central Virginia. Magnification: 40x Rock: Maidens Gneiss To view this mineral in plane p…