To get the jewel off, it is best to take the top half of the controller 
off and hold it in your hands like you would when playing a game.  
Apply back and forth pressure up and down with either hand like wringing
 out a towel.  Down with the right and up with the left, back and forth 
again and again.  You will see the glue around the dome begin to turn 
white and it will eventually come off.  Ive had them pop off after about
 three motions and others seem to take forever. As soon as it comes loose
 in an area, you can use a flat blade screwdriver or a butter knife to 
GENTLY pry off the dome
 



    Source: geocities.com/xboxinstigator