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
Mineral resource classification not achievable in some deposits. Generally the conversion of resources into reserves requires the application of various modifying factors, including: Mineral resource classification Mineral resource classification is the classification of mineral resources based on an increasing level of geological knowledge and confidence. Mineral deposits can be classified as: In common mining terminology , an "ore deposit" by definition must have an 'ore reserve', and may or may not have additional 'resources'. Classification, because it is an economic function, is governed by statutes, regulations and industry best practice norms. There are several classification schemes worldwide, however the Canadian CIM classification (see