Phlogopite
KMg3(AlSi3O10)(F,OH)2
Chemical name
Phlogopite
Mineral name
Phlogopite
Chemical formula
KMg3(AlSi3O10)(F,OH)2
Crystal system
monoclinic
Crystal Class
monoclinic-prismatic (2/m)
Space Group
C2/m
Unit cell
a [Å]:3.16
b [Å]:3.16
c [Å]:12.30
Formula units
Z=2
Frequent crystal surfaces
{001}
Twinning
composition twinning
Mohs hardness
2 - 2.5
Density [g/cm3]
2.75 - 2.97
Cleavage
perfect on (001) (basal)
Fracture / Tenacity
tough, flexible thin laminae
Color
brownish red, dark brown, yellowish brown, green, white
Streak
white
Transparency
transparent to translucent
Optical character
biaxial (-)
Refractive Index
nα=1.530-1.573; nβ=1.557-1.617; nΥ=1.558-1.618
Birefringence δ
0.028-0.045
Other
fluorescent