Porphyry, basalt and other monumental or building stone, whether or not roughly trimmed or merely cut, by sawing or otherwise, into blocks or slabs of a square or rectangular shape (excl. in the form of granules, chippings or powder, or already with the characteristics of setts, curbstones and flagstones, monumental or building stone of an apparent specific gravity of >= 2,5, granite and sandstone)