Apologies for the late update. Here are the requested dry pictures. Consensus from the original post is that this is a very convincing concrete replica. I did some more tests and hopefully this can clarify things and be useful for people in the future who are purchasing a questionable Molcajete. It holds water overnight but has one long pore in the rock that allows some water to leak out of the bottom. It can be scratched with a fork or knife but bot cut, it just makes a bit of white lines in the stone. It also smells like sulfur/burnt hair when the tejolote is ground into it.
Link to original post: https://www.reddit.com/r/mexicanfood/comments/1d4kab8/real_molcajete/
by cerciscanadensis1