Tellurium does exist in nature in its free form, but it is very rarely found this way. Most tellurium in nature occurs in nature and gold tellurides such as calaverite, krennerite, petzite, and sylvanite. Additional sources of tellurium can be used for isolation. One isolation process uses treatment of copper ore; this treatment process using electrolytic refining of copper forms anode sludges of tellurium. Tellurium can also be collected and isolated from dust that is emitted from the process of refining lead using a blast furnace.
Another isolation method which extracts tellurium from copper uses a multi-step chemical reaction process. The first step of the isolation process is to oxidize the tellurium-copper complex using sodium carbonate and oxygen to produce tellurite. The tellurite is then acidified with sulphuric acid to precipitate out of the solution in its dioxide form. The tellurium dioxide is then dissolved in sodium hydroxide, and electrolytic reduction is used to produce pure tellurium.