chalk
A limestone composed mainly of the calcareous tests of foraminifera, though containing, also, shells of larger mollusks. When much indurated, as in the valley of the Seine, it is used as a building material. (Sturgis, 1900)
A limestone composed mainly of the calcareous tests of foraminifera, though containing, also, shells of larger mollusks. When much indurated, as in the valley of the Seine, it is used as a building material. (Sturgis, 1900)