SteveS
Well, add glass beads to sandblasting material I believe. I was a little confused as I use sandblasting sand at times and never noticed glass beads in it, but I do use glass beads for reflection purposes but never incorporated them for blasting. On a safety note, I'm surprised they were left there as they are very slippery when walked on.
I'm going to try that experiment when the sun is shinning again.