Zircon

Crystal System
Tetragonal
Chemical Comp..
ZrSiO4
Color
Colorless to Pale Brown
Pleochroism
Weak to None
Cleavage
None
Relief
High
Birefringence
High 3rd/4th Order
2V ---
Optic Sign Positive
Twinning
None

Zircon has very high relief and high birefringence. It is often found as inclusions in biotite in metamorphic rocks along with the characteristic pleochroic halo.  Bi = Biotite; Zr = Zircon; Qz = Quartz.