Vaidurya or Cat's Eye is the name given to the variety of chrysoberyl which beautifully displays the phenomenon of chatoyancy.  The numerous inclusions line up to form very fine, parallel crystal needles.  Cat's eyes are always cut in cabachons to emphasize the eye effect.

Vaidurya or Cat's Eye harmonizes Ketu which is traditionally known as the "tail of the dragon".  In Jyotish, Ketu is the descending node of Chandra (Moon).  Its influences are similar to Mangal or Mars and include liberation, abstract thinking, asceticism, non-attachment, healing, moksha--enlightenment, wisdom and that which is hidden.  Ketu's influence in the physiology is represented by the tail of the caudate.  It's influence is over learning and emotions.