Iron pyrite is unstable when exposed to the oxidizing conditions prevailing at the Earths surface: iron pyrite in contact with atmospheric oxygen and water, or damp, ultimately decomposes into iron oxyhydroxides (ferrihydrite, FeO(OH)) and sulfuric acid (). This process is accelerated by the action of Acidithiobacillus' bacteria which oxidize pyrite to first produce ferrous ions (), sulfate ions (), and release protons (, or ). In a second step, the ferrous ions () are oxidized by  into ferric ions () which hydrolyze also releasing  ions and producing FeO(OH). These oxidation reactions occur more rapidly when pyrite is finely dispersed (framboidal crystals initially formed by sulfate reducing bacteria (SRB) in argillaceous sediments or dust from mining operations).