Uniaxial minerals will exhibit all four types of extinction discussed earlier.
The type is dependent on:
Depending on how the crystal is cut, and how its indicatrix is cut, dictates what will be seen in thin section.
Hexagonal minerals will exhibit the following forms prisms, pinacoids, pyramids and rhombohedrons which will exhibit prismatic, pinaciodal and rhombohedral cleavages.
The birefringence, interference colours and any cleavage displayed by hexagonal minerals is a function of how the grain has been cut.
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