ppl coarse-grained porphyrblasts 5*
ppl coarse-grained porphyrblasts 5*
xpl discordant plagioclase 5*
1. ppl w/chlorite alteration x5
2. xpl w/chlorite alteration x5
3. ppl min. pleoch. haloes N-S x5
4. ppl max. pleoch. haloes E-W x5
5. xpl birefringence E-W x5
6. xpl birefringence N-S x5
7. xpl maximum birefringence x10
8. xpl extinct
group mica
system monoclinic
formula K2(Mg,Fe)3AlSi3O10(OH,O,F)2
optic biaxial neg
Too-Vee 0 - 25¡
relief.1 moderate to high pos
min. index 1.522 / 1.696
color brown, green, orange
pleochroism yes
birefringence.1 0.030 - 0.070
cleavage yes {{ easily seen
elongation yes yesalong cleavage
extinction parallel, nearly parallel
angle 0 - 9¡
alteration commonly alters to chlorite and clay minerals
habit.1 columnar, tabular, platy
occurence metamorphic (contact, low to high grade), igneous
TwoV 1
relief 2 3
pleochroism.2 tan, green, brown
birefringence 9 12 13
cleavage.2 {001} perfect, controls fragment orientation