1. ppl relief and cleavage x10
1. ppl relief and cleavage x10
2. xpl relief; cleavage; max bir x10
3. xpl parallel extinction x10
ppl 10*
xpl 10*
ppl 10*
group mica
system monoclinic
formula KAl2(AlSi3O10)(OH)2
optic biaxial neg
Too-Vee 30 - 47¡
relief.1 moderate pos
min. index 1.552 / 1.623
color colorless, pink, green
pleochroism no
birefringence.1 0.036 - 0.049
cleavage yes
elongation yes
extinction parallel
angle 0 - 3¡
alteration not readily altered, clay minerals (sericite)
habit.1 columnar, tabular
occurence igneous (felsic), metamorphic (low to meduim grade, regional, pelite), hydrothermal
TwoV 1
relief 2
pleochroism.2
birefringence 9 13
cleavage.2 {001} perfect, controls fragment orientation