fieldstone n : stone that occurs naturally in fields; often used as building material
Fieldstone is a building construction material. Strictly speaking, it is stone collected from the surface of fields where it occurs naturally. In practice it is any architectural stone used in its natural shape and can be applied to stones recovered from the topsoil or subsoil. Although fieldstone is generally used to describe such material when used for exterior walls, it has come to include its use in other ways including garden features and interiors.