19 Stone, rock, clay and minerals; building and construction materials and elements made of sand, stone, rock, clay, minerals and concrete; minerals for use in construction; non-metallic minerals for building or construction; building glass; structural elements of glass; building materials consisting of glass; laminated building glass incorporating fine electrical conductors; infrared reflective glass for use in building; heat reflecting glass for building; thermal insulating glass for use in building; infrared-ray absorbing glass for building; feldspar (felspar); sand; sandstone; stone; rock grit; stone chippings; building materials made of rock fibres; building materials made of mineral fibres; porphyry (stone).