| Crystal System |
Trigonal |
| Chemical Comp.. |
SiO2 |
| Color |
Colorless |
| Pleochroism |
None |
| Cleavage |
None |
| Relief |
Low |
| Birefringence |
1st Order Gray/White |
| 2V | --- |
| Optic Sign | Positive |
| Twinning |
None observable |
Quartz has low relief, low birefringence, may show strained extinction (above), and is uniaxial positive.
If the thin section is a little thick, Quartz (Qz) can exhibit first-order-yellow birefringence.
