I have had that happen. I freaked out the first time because it was hard, yet black. I ran it under water and it was a clot. Completely normal. I get them every once in awhile, especially if I have a particularly heavy period. I have friends who miscarried early in pregnancy and felt no pain at all. They bled for about 9 days and that was it, an extended period. I've also had a friend miscarry in her 5th month and that was completely different. I have never asked her details about it and I never will, but she had severe cramping and pain. Anyway, while it might seem like it's a little off the wall to have a hard black discharge, it can be a normal occurrence, however, as with anything medical, if she is really really worried about just call the gynie and ask over the phone.