Bill Tindall, E.Tn.
"because the India is soft "

"India Stone" is a Norton trade name for aluminum oxide stones. I have one I have sharped kitchen knives on for decades and it is still fairly flat. I would call this stone exceptionally hard. Maybe there are differing grades of India hardness?

Silicon carbide of that particle size on glass is not the best choice for abrading. Silicon carbide is a brittle abrasive and readily crushed. Trapped between two similarly hard surfaces I would expect it to crush to finer abrasive quickly. No hands on experience but I would try it on Corian and see if it lasted longer and cut faster. Even better could be to sprinkle 220 grit diamond grits on Corian.