Yes, those are stones!! They do float and they also come in red, black, and yellow. My first flush yielded stones that were thumb tip size. I had one come out as large as an egg. The green slimy stuff is biliary sludge. I passed a ton of that also. From what I understand the sludge is a result of the breakdown of the stones, aided by fruit juice, and pineapple is supposed to be really good for that.