It is unlikely that much sulphur in coal comes from extraneous mineral matter. If the mineral matter contains sulphides, then they could provide a source of SO, and H,S to the coal, but amounts would usually be small. Even though pyrite is often found in parting material in coal, the sulphur probably originated in the coal. Partings formed by degradation of biomass may contain high concentrations of sulphur liberated from the biomass. Partings composed of extraneous mineral matter will have variable sulphur contents depending on the degree of marine influence and introduction of sulphur.