Leucite

1. ppl leucite x5

2. xpl leucite x5

group                                   feldspathoid
system                                  tetragonal
formula                                 KAlSi2O6
optic                                   uniaxial pos
Too-Vee                                 0¡
relief.1                                low neg
min. index                              1.508 / 1.511
color                                   colorless
pleochroism                             no
birefringence.1                         0.001 
cleavage                                no
elongation                              no
extinction                              incomplete
angle                                   0¡
alteration                              pseudoleucite (mixture of nepheline and K-spar)
habit.1                                 equant, pseudoisometric
occurence                               igneous (mafic and alkalic)
TwoV                                    
relief                                  4 
pleochroism.2                           
birefringence                           1 2
cleavage.2                              ( {110} not seen in thin section)