Actually, the paperweight could be based on a bird egg, and its "frothy" or "lumpy" surface could be correct, as some eggs are lumpy rather than smooth.
Check out some basic British bird eggs at
this site: Note that Song Thrush is blue with black spots and has a smooth surface but Blackbird egg is blue with a few spots and does have a lumpy surface. But I think they they can all vary a bit, so it's not a case of "one pic is right".