Galena 1–2% silver, a byproduct that far outweighs the main lead ore in revenue. Galena deposits often also contain significant amounts of silver as included silver sulfide mineral phases or as limited solid solution within the galena structure. These argentiferous galenas have long been the most important ore of silver. Galena deposits are found worldwide in various environments. Noted deposits include those at Freiberg in Saxony; Cornwall, the Mendips in Somerset, Derbyshire, and Cumberland in England; the Madan and Rhodope Mountains in Bulgaria; the Sullivan Mine of British Columbia; Broken Hill and Mount Isa in Australia; and the ancient mines of
National Mineral Development Corporation National Mineral Development Corporation </nowiki> NMDC Limited, previously known as National Mineral Development Corporation, is an Indian state-controlled mineral producer. It is 72.43% owned by the Government of India, under the administrative control of the Ministry of Steel. It is involved in the exploration of iron ore, copper, rock phosphate, limestone, dolomite, gypsum, bentonite, magnesite, diamond, tin, tungsten, graphite etc. It is India's largest iron ore producer and exporter producing more than 35 million tons of iron ore from 3 fully mechanized mines in Chhattisgarh and Karnataka. It also operates the only mechanized diamond mine in the country at Panna