Trirefringence

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

orthorhombic

System Class Name

AXES

Planes Center
Hermann-
Maugin
Symbols
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

orthorhombic

System Class Name

AXES

Planes Center
Hermann-
Maugin
Symbols
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

orthorhombic

System Class Name

AXES

Planes Center
Hermann-
Maugin
Symbols
2-Fold 3-Fold 4-Fold 6-Fold
Triclinic Pedial 1
Pinacoidal yes 1

Triclinic.pdf paper model

Source: http://webmineral.com/crystall.shtml

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