non magnetic

Heavy hard rock dulls a file quickly, oxidized but not magnetic

Dug this up the other day at an old home site near saltwater where I previously found 1700s coins. It?s non magnetic and it has weight to it. Might be silver and it?s about the size of a quarter. What do you think?

I live in minnesota. I was digging a hole to plant a tree in some relatively sandy and clay mixed soil. The shovel created a sort of cross section in the side of the hole when I noticed this rock about 2 feet down from the surface with a rust colored streak in the sand, verticly above it that...