So, I found this stone mantel behind the garage of the 100 year old house we just bought. It was mostly buried in the dirt. Fits our mantel perfect. Some sort of green stone. Was painted black at some point. I'm trying to strip the paint and want to refinish the stone. Area is southeast of Pittsburgh. Father of the man who built the house was an Italian stonemason that immigrated.

Don't think it's slate, has a tight grain and rings when you knock on it.

What kind of stone is this?