LAUNDER, in Mineralogy, a name given in Devonshire, and other places, to a long and shallow trough, which receives the powdered ore after it comes out of the box or cosier, which is a sort of mortar, in which it is powdered with iron pestles. The powdered ore, which is waisted into the launder by the water from the cosier, is always finest nearest the grate, and coarser all the way down.