Those marbles which are among the calcareous rocks, interconnected by cementitious materials and forms a layered structure. If the grain sizes are between 70 microns to 4 mm, it is called sandstone, while the larger grains turn into conglomerate stone. Marbles which are among calcareous rocks, are always layered & usually consists of very beautiful crystal lodes and fossils which gives a special beauty to this type of stone.