19 Stone, rock, clay and minerals; pitch, tar, bitumen and asphalt; spackling compounds; building and construction materials and elements, not of metal; refractory building materials, not of metal; concrete; cement facing; stones; mixes for mixing non-metallic building materials; liquid mixes for mixing concrete, cement facing and stones; liquid mixes for mixing non-metallic building materials; furnace linings, not of metal; refractory ceramic masses; ceramic refractory masses for lining metallurgical furnaces; prefabricated non-metallic building components; sand