Calcite

ppl rhombohedral sections 5*

xpl characteristic cleavage 5*

1. ppl secondary calcite x10

2. xpl secondary calcite x10

group                                   carbonate
system                                  hexagonal (triagonal)
formula                                 CaCO3
optic                                   uniaxial pos
Too-Vee                                 0¡
relief.1                                mod neg to high pos
min. index                              1.486 / 1.658
color                                   colorless
pleochroism                             no
birefringence.1                         0.172 
cleavage                                yes {1
elongation                              no
extinction                              inclined, symmetrical
angle                                   ***
alteration                              dolomite, quartz, opal, iron or manganese oxides
habit.1                                 granular, euhedral
occurence                               igneous (mafic), metamorphic (carbonate)

TwoV                                    
relief                                  5 1 2 3
pleochroism.2                           
birefringence                           9 13
cleavage.2                              {1011} perfect rhombohedral