Andalusite

ppl porphyroblasts 5*

xpl low birefringence 5*

ppl within minor crenulations 10*

xpl illmenite crenulated 10*

group                                   aluminosilicate
system                                  orthorhombic
formula                                 Al2SiO5
optic                                   biaxial neg
Too-Vee                                 71 - 88¡
relief.1                                mod to high pos
min. index                              1.629 /1.650
color                                   colorless, pink, green
pleochroism                             yes 
birefringence.1                         0.009 - 0.013
cleavage                                yes
elongation                              yes
extinction                              parallel, symmetrical
angle                                   0¡
alteration                              sericite, chlorite, sillimanite, kyanite
habit.1                                 prismatic, tabular, fibrous, anhedral
occurence                               metamorphic (low to medium grade, contact, regional), hydrothermal (pegmatites)
TwoV                                    2
relief                                  2 3
pleochroism.2                           pink, green, yellow
birefringence                           1 3 4 5 6
cleavage.2                              {110} two good at right angles