Kyanite

ppl 10*

xpl 10*

group                                   aluminosilicate
system                                  triclinic
formula                                 Al2SiO5
optic                                   biaxial neg
Too-Vee                                 78 - 84¡
relief.1                                high pos
min. index                              1.710 / 1.734
color                                   colorless, blue
pleochroism                             yes
birefringence.1                         0.012 - 0.016
cleavage                                yes
elongation                              yes
extinction                              inclined
angle                                   0 - 30¡
alteration                              sericite, chlorite, andalusite, sillimanite
habit.1                                 bladed, columnar
occurence                               metamorphic (pelite, schist, gneiss) , hydrothermal (pegmatite),  
TwoV                                    2
relief                                  3
pleochroism.2                           violet, blue
birefringence                           5 6 7
cleavage.2                              {100} perfect, {010} good