40d:Block
From Dwarf Fortress Wiki
A block is a sub-type of building material. Stone and wood can be shaped into blocks at the Mason's workshop or Carpenter's workshop. Glass can be formed as blocks at a Glass Furnace, and metal blocks can be made at the forge from a single metal bar (or, in the case of adamantine, from four wafers).
A single block is required in order to build a well, pump, or ashery. Blocks can also be used in place of raw stone or wood in roads, bridges, and other major constructions (but not in items like crafts or furniture), but the difference is purely in the value. A pillar made out of normal stone is called a rough pillar.
Blocks, unlike raw stone or wood, can stack in bins in bar/block stockpiles.
Blocks have a base value of 5, compared to the raw material value of 3 for stone, wood or glass; metal bars already have a base value of 5. Blocks do not have quality levels.
Stone blocks are sometimes used as materials during strange moods.
