The division of light into three components, the smallest of which is known as the ordinary ray and the largest of which is known as the extraordinary ray, found in materials which have three different indices of refraction in different directions. Crystals exhibiting trirefringence are orthorhombic, monoclinic, and triclinic. They are therefore trirefringent and are known as biaxial.
Source: http://wolfram.com
orthorhombic
| System | Class Name |
AXES |
Planes | Center |
|
|||
| 2-Fold | 3-Fold | 4-Fold | 6-Fold | |||||
| Orthorhombic | Pyramidal | 1 | – | – | – | 2 | – | mm2 |
| Disphenoidal | 3 | – | – | – | – | – | 222 | |
| Dipyramidal | 3 | – | – | – | 3 | yes | 2/m 2/m 2/m | |
Orthorhombic.pdf paper model
monoclinic
| System | Class Name |
AXES |
Planes | Center |
|
|||
| 2-Fold | 3-Fold | 4-Fold | 6-Fold | |||||
| Monoclinic | Domatic | – | – | – | – | 1 | – | m |
| Sphenoidal | 1 | – | – | – | – | – | 2 | |
| Prismatic | 1 | – | – | – | 1 | yes | 2/m | |
Monoclinic.pdf paper model
triclinic
| System | Class Name |
AXES |
Planes | Center |
|
|||
| 2-Fold | 3-Fold | 4-Fold | 6-Fold | |||||
| Triclinic | Pedial | – | – | – | – | – | – | 1 |
| Pinacoidal | – | – | – | – | – | yes | 1 | |
Triclinic.pdf paper model
Source: http://webmineral.com/crystall.shtml
