He then hammers the tough, low-carbon steel, which he has shaped so it will ... Sometimes called "water stones," these tools are typically composed of hard silicate particles suspended in clay.

durable metal with a low carbon content. Items such as locks, bolts, tools, and fences are crafted out of this metal. Wrought iron bars were also sold and traded to be later converted into steel ...

The carbon saving comes presumably in the lower energy cost from not smelting iron to make steel, as well as the need for less concrete due to the lightness. All we need now is a low-carbon ...