Joe, Thanks so much for responding.
This guy came to me as a rescue along with a few other critters. I have read up on his care, but it's not a species that I am closely familiar with.

What does the term "s WC adult" mean? I am including a couple of shots, but the belly shot may not be too helpful for sexing. I was just cleaning the tank, so he's off hiding out right now
I did notice a few rubs on him besides the lips, probably from being handled prior to being handed over. I am also wondering if this is his original tail... the color is so different, but very attractive nonetheless.

The stone is more likely to be black slate, it's part of a waterfall in his enclosure.
The obsidian comment reminded me of Shawshank Redemption. LOL.