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
Broken Hill ore deposit hornblende schists. The ore consists of massive, recrystallised sphalerite-rich, galena-sphalerite and galena-rich sulfide lenses in folded horizons, known as No. 2 Lens Formation and No.3 Lens Formation. Both have distinctive metal ratios and gangue minerals. The ore boundaries are parallel to the bedding planes. According to Gustafson, "There is evidence that the ore has been introduced into an old, already folded, rock and has replaced certain favourable layers of that rock, particle by particle, with large tonnages of garnet, rhodonite, fluorite, marmatite (and wurtzite), galena, and other minerals that constitute the orebodies." The Potosi-Footwall Gneiss is found on both sides