Coarse, gravel-like mine waste produced during the milling and concentration of lead and zinc ores. It consists mostly of chert, limestone, and dolomite fragments left over after the heavy sulfide minerals are separated, often accumulating in massive surface piles near historic mining districts.
Heard on the job
We need to grade the haul road with a fresh layer of chat before the rains start.
Insider tip
In the American Midwest, chat was widely sold as aggregate for road construction and railroad ballast, leading to widespread environmental remediation efforts due to residual heavy metals.