Olivine

xpl 10*

ppl 20*

xpl 20*

ppl 20*

xpl 20*

ppl 5*

1. xpl 3rd order birefringence x5

2. ppl ideal crystal shape x5

3. xpl maximum birefringence x5

4. xpl extinction x5

7. ppl olivine in pyroxence x5

8. xpl olivine in pyroxence x5

group                                   olivine
system                                  orthorhombic
formula                                 (Fe,Mg)2SiO4
optic                                   biaxial neg / pos
Too-Vee                                 46 - 98¡
relief.1                                high pos
min. index                              1.636 / 1.879
color                                   colorless, yellow
pleochroism                             yes
birefringence.1                         0.033 - 0.052
cleavage                                no
elongation                              yes
extinction                              parallel
angle                                   0¡
alteration                              iddingsite, chlorophaeite
habit.1                                 subequant, anhedral (aggregates), euhedral
occurence                               igneous (granitic, volcanic, mafic, ultramafic) meta- morphic (skarn), sedimentary
TwoV                                    1 2
relief                                  3
pleochroism.2                           yellow, orange
birefringence                           9 12 13
cleavage.2                              ( {010}, {110} not seen in thin section)