Anorthoclase

1. ppl anorthoclase x5

2. xpl anorthoclase x5

3. ppl anorthoclase x5

group                                   tectosilicate
system                                  triclinic
formula                                 (K,Na)AlSi3O8
optic                                   biaxial neg
Too-Vee                                 0 - 55¡
relief.1                                low neg
min. index                              1.519 / 1.536
color                                   colorless
pleochroism                             no
birefringence.1                         0.005 - 0.008
cleavage                                yes  
elongation                              no
extinction                              inclined
angle                                   ***
alteration                              ***
habit.1                                 tabular, columnar
occurence                               igneous (felsic)
TwoV                                    1 2
relief                                  4
pleochroism.2                           
birefringence                           1 2 3 
cleavage.2                              ***