A historic method of breaking rock by building a large wood fire against the working face. The intense heat caused the rock to expand and crack, a process often accelerated by throwing cold water or vinegar onto the hot stone. It was the primary method for driving tunnels through hard rock before the invention of chemical explosives.
Heard on the job
You can still see the smooth, rounded soot-stained roofs in the adit where they used firesetting to advance the heading.
Related terms
Adit
A horizontal or near-horizontal tunnel driven from the surface into a mountain or hillside to access an ore body.
Lode
A defined vein or tabular deposit of valuable metallic ore embedded within barren rock.
Stope
To excavate ore from an underground block by driving a series of steps or horizontal cuts.