I bought these "pebbles" recently. They're green aventurine. I've been mostly working with my copper tube beads but I ran out of them a few days ago, and am waiting to get more. So, in the meantime, I picked up the pebbles and started experimenting with them. I like the way they break up the grid in an otherwise very rigid structure. The one on the left is just plain RAW. The middle one is RAW too, but with a triangular cross section, so that there are just 3 squares in each row, instead of 4. It makes the tube a bit smaller. But in both of them, and especially the one with the triangles, there's a lot of thread showing. I'm using monofilament, so it doesn't show too much in the picture, but the irregularity of the beads necessarily means that more thread shows than I like. The 3rd on is better that way, because I was using a structure of hexagons instead of squares. You get a bigger, more open tube, with places where you can see through the tube, and not as much thread showing. Not sure exactly where I'll go with all this, but I kind of like the Payday candy bar look of it.
PS one other thing I should mention--I tried a couple of spherical shapes (a dodecahedron and a cuboctahedron) and they came out looking like lumps.