Is there any way to repair a Corion countertop that has deep cracks that can't be sanded out?

Hello Judy.
Your Corian can be repaired but it will have to be done by a qualified, preferably certified Corian fabricator or a solid surface repair specialist. What state are you in? I can probably help you find a qualified person to assist you in your state.

Thanks,
Bryan

Has the crack gone all of the way through the top, can you see/fel it on the underside?