Mineral - Muscovite
Muscovite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
KAl₂[(OH,F)₂|AlSi₃O₁₀]
Unit Cell
a=5.19 b=9.04 c=20.08 β=95° Z=4
Physical Properties
Hardness
2.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}
Fracture
smooth
Tenacity
Brittle
Optical Properties
Color
brownredyellowcolorless
Birefringence
0.042
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/c (15)
Habit
leafy, book-shaped, dipyramidal, lamellar, platelet-shaped
Formation
(1) Magmatic, formed by crystallization from silica-rich plutonic melts (granites, pegmatites) under moderate to high pressures.
(2) Metamorphic, formed by the transformation of clay minerals or feldspars in the green schist to amphibolite facies (mica schists, gneisses).
(3) Hydrothermal, formed by the alteration of aluminum silicates in residual magmatic solutions (greis formation).
Paragenesis
Twinning
Rarity
Very common
Synonyms
Muscovite
Composition
Elements
Mass
SiO₂
45.87
Al₂O₃
38.69
MgO
0.10
Na₂O
0.64
K₂O
10.08
H₂O
4.67
Canada (Dana 1895)
Groups and Members
Mica-Group