 The Hertfordshire Puddingstone is characterized by silica-cemented flint gravel that is brown to deep red in color and often exhibits black exteriors and thin rinds on cut or polished surfaces.It typically occurs scattered across the land surface as isolated concretion-like masses in the area of Hertfordshire and Plumstead Common, England.Large masses of Hertfordshire Puddingstone often occur within local Pleistocene glacial tills.