Paragonite

xpl 10*

ppl 10*

group                                   mica
system                                  monoclinic
formula                                 NaAl2(AlSI3O10)(OH,F)2
optic                                   biaxial neg
Too-Vee                                 30 - 47¡
relief.1                                mod pos
min. index                              1.552 / 1.623
color                                   colorless
pleochroism                             no
birefringence.1                         0.036 - 0.049
cleavage                                yes
elongation                              yes
extinction                              parallel
angle                                   0¡ 
alteration                              not readily altered, clay minerals
habit.1                                 tabular 
occurence                               igneous (granitic, volcanic), metamorphic (low to high grade), sedimentary (clastic)
TwoV                                    1 2
relief                                  2
pleochroism.2                           
birefringence                           9 13
cleavage.2                              {001} perfect