… Slate, whether or not roughly trimmed or merely cut, by sawing or otherwise, into blocks or slabs of a rectangular (including square) shape. …
Explanatory notes
… cut, by sawing or otherwise, into blocks or slabs of a rectangular (including square) shape. Slate, which splits readily into thin sheets, is generally bluish‑grey but … (e.g., with a wire strand), into blocks or slabs of a rectangular (including square) shape. Slate powder and waste …