Lithium Mica
K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2
Chemical name
Lithium Mica
Mineral name
Lepidolite
Chemical formula
K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2
Crystal system
monoclinic
Crystal Class
monoclinic-prismatic (2/m)
Space Group
C2/m
Unit cell
a [Å]:5.21
b [Å]:8.97
c [Å]:20.16
Formula units
Z=2
Twinning
rare, composition plane on {001}
Mohs hardness
2.5 - 3
Density [g/cm3]
2.8 - 2.9
Cleavage
perfect on {001}
Fracture / Tenacity
uneven
Color
pink, purple, rose-red, violet-gray, yellowish, white, colorless
Streak
white
Transparency
transparent to translucent
Optical character
biaxial (-)
Refractive Index
nα=1.525-1.548; nβ=1.551-1.580; nΥ=1.554-1.586
Birefringence δ
0.029 - 0.038
Pleochroism δ
moderate to strong