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
Ore genesis classified hydrothermal deposits as "hypothermal", "mesothermal", "epithermal", and "telethermal". Epithermal deposits are hydrothermal ore deposits formed at low temperatures (50-200 °C) near the Earth´s surface (<1500 m), that fill veins, breccias, and stockworks. The age of formation of epithermal deposits in México is currently being investigated. "As they require the conjunction of specific environmental conditions to form, particular mineral deposit types tend to occupy specific geodynamic niches," therefore, this page has been organised by metal commodity. It is also possible to organise theories the other way, namely according to geological criteria of formation. Often ores of the same metal can