wˌɛn ðə ɹˈɑːk kəntˈeɪnɪŋ paɪɹˈaɪɾiːz pˈaɪɹaɪt ɪz wˈɛðɚd, ðɪ ˌɑːksɪdˈeɪʃən ʌvðə pˈaɪɹaɪt wɪð sˈʌbsᵻkwənt bæktˈɪɹiəl ɹᵻdˈʌkʃən ʌvðə sˈʌlfeɪt ˈaɪɑːn pɹədˈuːsᵻz hˈaɪdɹədʒən sˈʌlfaɪd ˈeɪtʃ tˈuː z.
When the rock containing pyrites (pyrite) is weathered, the oxidation of the pyrite with subsequent bacterial reduction of the sulfate ion produces hydrogen sulfide (H2S).