There are basically two types of ore minerals: oxides and sulfides. From these, the metals of interest will be extracted: iron, zinc, copper, tin, lead etc. In the past, the unwanted sulfide minerals may have been converted to sulfur dioxide and released into the atmosphere. Some of it may have been used to make sulfuric acid. Some of it has been dumped and is slowly oxidizing and forming sulfuric acid in the environment, to the detriment of the environment.

In the past, some sulfide ores have been burned as a fuel to rapidly oxidize the minerals to make downstream extraction of the desired metal easier. Such burning produced vast quantities of sulfur dioxide which produced acid rain, which then kill the surrounding vegetation resulting in a denuded and much damaged landscape.

Eventually, most metals that have been extracted from minerals will oxidize over time.