I've tried building a simple rig where there is an attractor parented to the camera to pull the crystal, then a negative attractor with a fall-off to restrict it if it gets too close to camera. No luck.
Align object to Spline, parent spline to the camera, enable objects "follow position" so it keeps up with camera. No luck. Results are very rigid and crystal doesn't tumble "head over heels" but instead is dragged along ground.