Vesuvianite

xpl 20*

ppl 10*

group                                   sorosilicate
system                                  tetragonal
formula                                 see properties
optic                                   uniaxial neg
Too-Vee                                 0¡
relief.1                                high pos
min. index                              1.702 / 1.795
color                                   colorless, brown,  yellow
pleochroism                             yes
birefringence.1                         0.001 - 0.020
cleavage                                yes
elongation                              yes
extinction                              parallel
angle                                   0¡
alteration                              not readily altered

habit.1                                 prismatic,  acicular, anhedral
occurence                               metamorphic (contact, carbonate), hydrothermal (mafic, ultramafic)
TwoV                                    
relief                                  3
pleochroism.2                           yellow
birefringence                           1 2 3 4 5 6 7 8
cleavage.2                              {110}, {100}, {001} poor, seldom seen