I'm sure one of the more experienced flushers will comment here, but this sounds really good to me. Sounds like the black in the poop matches the stones. Also don't know what the consistency is of the blackish stuff, but what i noticed that blackish rubbery stuff came out after i flushed. This matches the description for mucoid plaque, so I take it that the Epsom Salts
got rid of some of the gunk in your, and my, intestines.
I'm a new flusher - what I noticed is that my stones had a huge, bad smell, and that my Body Odor
has been exactly matching that gross stone smell for a number of days. So I think that the ways in which the s*** that is released after a flush comes out of the body, is manifold.