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 Mg (16,500 tons) from 1990 production. Except for mines in Missouri ...