concretions of a rather flat and small botryoidal external figure of an iron black colour, and highly metallic lustre, resembling grey manganese, or black hematitic iron ore.
Intermixed with these are small arborescent tufts, about a quarter of an inch in length, adherent by their base to the mass of coak, each branch of which, when examined by the microscope, appears composed of minute botryoidal shoots.
