Sanidine

1. ppl sanidine in tachyte x5

2. xpl sanidine in trachyte x5

group                                   feldspar
system                                  monclinic
formula                                 (K,Na)AlSi3O8
optic                                   biaxial neg
Too-Vee                                 0 - 47¡
relief.1                                low neg
min. index                              1.514 / 1.533
color                                   colorless
pleochroism                             no
birefringence.1                         0.005 - 0.008
cleavage                                yes
elongation                              no
extinction                              inclined
angle                                   5 - 15¡
alteration                              sericite, clay
habit.1                                 columnar, tabular
occurence                               igneous (felsic, volcanic), metamorphic (high grade), sediment
TwoV                                    1
relief                                  4
pleochroism.2                           
birefringence                           1 2 3
cleavage.2                              {001} perfect, {010} good, intersect 90 deg