After the last S#X rock, I was going to stay away from this one. However..... looking at the first picture, I find it real interesting there are two sets of parallel indentations. If you look at them, they line up perfectly across from each other. Not only that, if you look close, both sets angle inward. To me, natural erosion could not have done this. I also have never seen drill holes for blasting this close together or for that matter angled like that. I am gong to suggest another theory... man made. What if this was mounted between the forks of a Y shaped stick. Could it have been used as some sort of hammer or some other type tool? You also have to take into account were it was found. I wouldn't discard it as a S#X rock to quickly. OK, that is my two cents worth.