Some questions for you. Where did you find it? Location tells us about the region you found your specimen. Geological features will give us a clue as well as a descriptive phrase like I found this grey rock in a dry riverbed near Mt. St. Helen. Also, our people here are from everywhere and they may have specific knowledge. It scratches easily and seems fragile. It is magnetic. It is very heavy for its size. These kind of descriptive sentences allow us to narrow down possibilities to identify your rock.