When a mineral is in extinction, what can we say about the orientation of its fast and slow-vibration directions?

The vectorial relationship characterizing the collaboration between a light wave and a crystal through which it passes is represented by the inborn direction of cross-section electrical vectors and the heading of the wave's electric vector segment.

However, when light enters a non-equal pivot, it is refracted into two beams, each spellbound with the vibration headings situated at right edges commonly opposite one another and going at various speeds. This unusual conduct, as talked about above, is ascribed to the course of action of molecules in the crystalline grid.

so whats the answer? ?