https://lemmy.world/pictrs/image/d6b8bc87-d0cf-4bb8-bfa6-787e09524093.png This is a trimmed chestnut. They grow a material similar to a nail or horse hoof - ergots are similar, but in a different location. When they get big you just peel or clip it off. They can smell a bit strong when you trim them, but hooves smell worse when the farrier comes out!