Roasting is a preliminary metallurgical process where sulfide ores are heated in the presence of excess air to a temperature below their melting point. The heat causes the sulfur in the ore to react with oxygen and escape as sulfur dioxide gas, converting the metal sulfide into a metal oxide. This prepares the ore for subsequent smelting and reduction operations.
Heard on the job
We need to roast the zinc blende thoroughly before it goes into the retorts, or the extraction yield will tank.