12.18 Leadbearing Ore Crushing And Grinding 12.18.1 General1 Leadbearing ore is mined from underground or open pit mines. After extraction, the ore is processed by crushing, screening, and milling. Domestic lead mine production for 1991 totaled 480,000 megagrams (Mg) (530,000 tons) of lead in ore concentrates, a decrease of some 15,000 …Web