Gomedhaka or hessonite is a variety of  grossular garnet.  It has good lustre and looks transparent.  The color is  brownish-orange and is often called "cinnamon stone".  These gems are often given step or mixed cuts.  Hessonite garnets are found especially in Sri Lanka.
Gomedhaka or Hessonite Garnet represents Rahu, the ascending node of the moon.  Its natural significations include worldly desires, worldly benefits, laziness, gratification, and ignorance.  It is by nature unpredictable and creates sudden changes and influences, rigidity and passion.  It is similar to Sani or Saturn in its nature and influence. Traditionally, rahu is known as the "head of the dragon".  In the human physiology, rahu corresponds to the head of the caudate.  The caudate is involved in the control of the saccadic eye movements (the abrupt short shifts of focus in the eyes).  The caudate influences memory in relation to orientation in space.  The caudate is responsible for our ability to change behavior patterns.