Sparkles

I recently bought a bistro table off of craigslist. The top is simulated slate-not sure of the material, but it is quite heavy. Anyway, it looks like somebody did a craft project on it with green sparkles, they are everywhere! They come off if I sit there and scratch them with my nail, but that would take forever! Any suggestions? I have tried with a plastic scrubbie, as well as baking soda and water paste and a scrub brush, but the removal is minimal at best. Any suggestions, please?!!!!!