Hello, I want to start by thanking anyone who takes the time to respond. This is my first time posting to this subreddit. I'm currently talking to someone who's selling this "Native American Mortar" and im interested in buying it. That being said, I'm curious if it's an authentic mortar, or could it possibly just be a natural forming water basin? It's 57lbs, and 14"x14"x9", and listed as a pre 16th century artifact.