Apatite

1. ppl basal sections x10

2. xpl basal sections x10

3. ppl long sections x10

4. xpl maximum birefringence x10

5. xpl parallel extinction x10

group                                   phosphate
system                                  hexagonal
formula                                 Ca5(PO4)3(F,OH,Cl)
optic                                   uniaxial neg
Too-Vee                                 0¡
relief.1                                moderate to high pos
min. index                              1.633 / 1.665
color                                   colorless
pleochroism                             no
birefringence.1                         0.001 - 0.007
cleavage                                yes  basal cleavage {0001}, v. poor prismatic cleav. {1010}
elongation                              yes
extinction                              parallel 
angle                                   0¡
alteration                              not readily altered
habit.1                                 equant, prismatic, columnar
occurence                               igneous (accessory)
TwoV                                    
relief                                  2 3
pleochroism.2                           
birefringence                           1 2 3
cleavage.2                              {0001} basal, poor, {1010} very poor