A black, heavy material by-product from smelting for which there was no technological capacity for further use in antiquity but became exploitable in industrial times. Slag, which often contained as much as 12 percent of its weight in silver lead, was utilised in the new metallurgical activity in the Lavreotiki area from 1865 onwards. The area’s mineral wealth by site and type is analysed here: www.mindat.org/loc-14187.html