Hello, Could I please get assistance with a rock identification. I came across this one in the southwest part of the U.S. While I see a lot of slag from old mines, this rock appears to be something different than slag. Besides, it was the only dark colored rock I came across that day. It also appears to have grooves of some kind. This is my second post asking for assistance with a rock identification, so just a reminder, I do historical research and at times, come across (what I consider) odd rocks that don't match anything else in the area. Please see the attached photos and let me know your thoughts or if you have additional questions. Thank you in advance.